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Natural killer (NK) cells include different subsets with diverse effector capacities that are poorly understood in the context of parasitic diseases. Here, we investigated inhibitory and activating receptor expression on NK cells in patients with cutaneous leishmaniasis (CL) and explored their phenotypic and functional heterogeneity based on CD57 and NKG2C expression. The expression of CD57 identified NK cells that accumulated in CL patients and exhibited features of senescence. The CD57+ cells exhibited heightened levels of the activating receptor NKG2C and diminished expression of the inhibitory receptor NKG2A. RNA sequencing analyses based on NKG2C transcriptome have revealed two distinct profiles among CL patients associated with cytotoxic and functional genes. The CD57+NKG2C+ subset accumulated in the blood of patients and presented conspicuous features of senescence, including the expression of markers such as p16, yH2ax, and p38, as well as reduced proliferative capacity. In addition, they positively correlated with the number of days until lesion resolution. This study provides a broad understanding of the NK cell biology during Leishmania infection and reinforces the role of senescent cells in the adverse clinical outcomes of CL. Natural killer (NK) cells include different subsets with diverse effector capacities that are poorly understood in the context of parasitic diseases. This study provides a broad understanding of the NK cell biology during Leishmania infection and reinforces the role of senescent cells in the adverse clinical outcomes of cutaneous leishmaniasis. Graphical Abstract (A) NK subsets present opposite immune and senescence features in cutaneous leishmaniasis. (B) Expansion of cytotoxic NKG2C + CD57 + NK cells is associated with increased lesional healing delay. Spearman's rank correlation (ρ) between cell subsets frequencies and patient stratified by CD57 and NKG2C expression and lesional healing time (days) taken by cutaneous leishmaniasis patients. The graphs show a median with 95% confidence. The P values were calculated by comparing each treatment round set between the NK cell subsets using RM-one-way ANOVA and Benjamin and Hochberg method. *P < 0.05, **P < 0.01, ***P < 0.001. [ABSTRACT FROM AUTHOR]

Summary: Natural killer (NK) cells play a crucial role in controlling viral infections. The ability to kill infected cells without prior immunization, yet being tolerant to self, healthy cells, depends on the balance of germ-line encoded surface receptors. NK-cell receptors are divided into either activating, leading to activation of NK cell and its cytotoxic and pro-inflammatory activity, or inhibitory, providing tolerance for a target cell. The signals from inhibitory receptors dominate and NK-cell activation requires stimulation of activating receptors. In viral infections, NK-cell interaction with infected cells can result in activation, memory-like NK-cell differentiation, or NK-cell exhaustion, which constitutes one of the viral immune evasion mechanisms. All of these states are associated with the modulation of NK-cell receptor expression. In this review, we summarize the current knowledge of NK-cell receptors and their role in viral infection control, as well as the alterations of their expression observed in acute or chronic infections. We present recently discovered SARS-CoV-2-mediated modulation of NK-cell receptor expression and compare them with other human viral infections. Finally, since modulation of NK-cell receptor activation gives a promising addition to currently used antiviral therapies, we briefly discuss the clinical significance and future perspective of the application of agonists or antagonists of activating and inhibitory receptors, respectively. In sum, our review shows that although much is known about NK-cell receptor biology, a deeper understanding of NK-cell receptors role in viral infections is still needed. This review summarizes recent knowledge on NK cell receptor alterations mediated by viral infections, along with the mechanisms responsible for this modulation. We present recently discovered SARS-CoV-2-mediated modulation of NK cell receptor expression and compare them with other human viral infections. Graphical Abstract [ABSTRACT FROM AUTHOR]

Gestational diabetes mellitus (GDM) is a frequent and serious complication of pregnancy, often associated with obesity. Metabolic dysfunction and metainflammation are evident in both obesity and GDM. In this cross-sectional study, we aimed at defining the direct contribution of the immune system in GDM, across the main metabolic tissues, specifically focussing on elucidating the roles of obesity and GDM to the clinical outcome. Using immunoassays and multicolour flow cytometry, cytokine profiles and immune cell frequencies were measured in maternal circulation and central metabolic tissues [placenta and visceral adipose tissue (VAT)] in GDM-diagnosed (n = 28) and normal glucose tolerant (n = 32) women undergoing caesarean section. Participants were sub-grouped as non-obese [body mass index (BMI) < 30 kg/m2] or obese (BMI ≥ 30 kg/m2). Unsupervised data analysis was performed on the flow cytometry data set to identify functional alterations. GDM obese participants had significantly elevated circulating IL-6 and IL-17A levels. GDM non-obese participants had elevated circulating IL-12p70, elevated placental IL-17A, and VAT IFN-γ production. Unsupervised clustering of immune populations across the three biological sites simultaneously, identified different NK- and T-cell phenotypes that were altered in NGT obese and GDM non-obese participants, while a classical tissue monocyte cluster was increased in GDM obese participants. In this study, there was significant evidence of subclinical inflammation, and significant alterations in clusters of NK cells, T cells, and tissue monocyte populations in GDM. While increased adiposity assimilates with increased inflammation in the non-pregnant state, this overt relationship may not be as evident during pregnancy and warrants further examination in future longitudinal studies. Gestational diabetes mellitus (GDM) is a frequent and serious complication of pregnancy, often associated with obesity. In this study, there was significant evidence of subclinical inflammation in maternal circulation and in both placental and visceral adipose tissue. However, no direct causal role could be attributed to any specific immune cell population in GDM. Graphical Abstract [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells were reported to be involved in the pathogenesis of primary antiphospholipid syndrome (pAPS). Immunosuppressive receptor T-cell immunoreceptor with Ig and ITIM domains (TIGIT) and activating receptor cluster of differentiation 226 (CD226) are specifically expressed on NK cells with competitive functions. This study aims to investigate the expression diversities of CD226/TIGIT on NK subsets and their associations with NK subsets activation phenotypes and potential clinical significance, furthermore, to explore potential cause for CD226/TIGIT expression diversities in pAPS. We comparatively assessed the changes of CD56brightNK, CD56dimNK, and NK-like cells in 70 pAPS patients compared with control groups, including systemic lupus erythematosus, asymptomatic antiphospholipid antibodies carriers (asymp-aPLs carriers), and healthy controls and their expression diversities of CD226/TIGIT by flow cytometry. CD25, CD69, CD107α expression, and interferon gamma (IFN-γ) secretion levels of NK subsets were detected to determine the potential association of CD226/TIGIT expression with NK subsets phenotypes. CD226/TIGIT expression levels were compared among different subgroups divided by aPLs status. Moreover, in vitro cultures were conducted to explore the potential mechanisms of CD226/TIGIT expression imbalance. CD56brightNK and CD3+CD56+NK-like cells were significantly increased while CD56dimNK cells were obviously decreased in pAPS, and CD56brightNK and NK-like cells exhibited significantly higher CD226 but lower TIGIT expressions. CD226+CD56brightNK and TIGIT-CD56brightNK cells show higher CD69 expression and IFN-γ secretion capacity, and CD226+NK-like and TIGIT-NK-like cells showed higher expressions of CD25 and CD69 but lower apoptosis rate than CD226− and TIGIT+CD56brightNK/NK-like cells, respectively. The imbalanced CD226/TIGIT expressions were most significant in aPLs triple-positive group. Imbalanced expressions of CD226/TIGIT on CD56brightNK and NK-like cells were aggravated after interleukin-4 (IL-4) stimulation and recovered after tofacitinib blocking. Our data revealed significant imbalanced CD226/TIGIT expressions on NK subsets in pAPS, which closely associated with NK subsets phenotypes and more complicated autoantibody status. CD226/TIGIT imbalanced may be affected by IL-4/Janus Kinase (JAK) pathway activation. Levels of CD56bright NK and natural killer (NK)-like cells were significantly elevated with imbalanced expressions of CD226 and T-cell immunoreceptor with Ig and ITIM domains (TIGIT), exhibited as higher expression of CD226 but lower expression of TIGIT. Imbalanced expression of CD226 and TIGIT were closely associated with activated phenotypes and stronger functions of NK subsets, and this imbalance was most prominently in pAPS patients with complicated serum antiphospholipid antibodies status. Altered CD226/TIGIT expression on CD56bright NK and NK-like cells may be aggravated by stimulation of IL-4 and recovered by JAK inhibitor tofacitinib. Graphical Abstract [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells are innate lymphocytes capable to recognize and kill virus-infected and cancer cells. In the past years, the use of allogeneic NK cells as anti-cancer therapy gained interest due to their ability to induce graft-versus-cancer responses without causing graft-versus-host disease and multiple protocols have been developed to produce high numbers of activated NK cells. While the ability of these cells to mediate tumor kill has been extensively studied, less is known about their capacity to influence the activity of other immune cells that may contribute to a concerted anti-tumor response in the tumor microenvironment (TME). In this study, we analyzed how an allogeneic off-the-shelf cord blood stem cell-derived NK-cell product influenced the activation of dendritic cells (DC). Crosstalk between NK cells and healthy donor monocyte-derived DC (MoDC) resulted in the release of IFNγ and TNF, MoDC activation, and the release of the T-cell-recruiting chemokines CXCL9 and CXCL10. Moreover, in the presence of prostaglandin-E2, NK cell/MoDC crosstalk antagonized the detrimental effect of IL-10 on MoDC maturation leading to higher expression of multiple (co-)stimulatory markers. The NK cells also induced activation of conventional DC2 (cDC2) and CD8+ T cells, and the release of TNF, GM-CSF, and CXCL9/10 in peripheral blood mononuclear cells of patients with metastatic colorectal cancer. The activated phenotype of MoDC/cDC2 and the increased release of pro-inflammatory cytokines and T-cell-recruiting chemokines resulting from NK cell/DC crosstalk should contribute to a more inflamed TME and may thus enhance the efficacy of T-cell-based therapies. Allogeneic off-the-shelf cord blood stem cell-derived NK cells engage in a crosstalk with monocyte-derived DC (MoDC) resulting in MoDC activation and in the release of pro-inflammatory cytokines and chemokines. Similar results were also obtained in the presence of PgE2, where the NK cells could mostly antagonize the detrimental effect of IL-10 on MoDC maturation, and in peripheral blood of patients with colorectal cancer, where the NK cells induced the activation of conventional DC2 (cDC2) and CD8 + T cells, and the release of TNF, GM-CSF, and CXCL9/10. Our data show that allogeneic NK cells have the potential to induce dendritic cell activation and thereby trigger a pro-inflammatory response, even under cancer-associated immune suppressive conditions. Graphical Abstract [ABSTRACT FROM AUTHOR]

The immune system of semi- (from ≥105 to <110 years old) and supercentenarians (≥110 years old), i.e. oldest centenarians, is thought to have characteristics that allow them to reach extreme longevity in relatively healthy status. Thus, we investigated variations of the two principal subsets of Tγδ, Vδ1, and Vδ2, and their functional subsets using the markers defining Tαβ cells, i.e. CD27, CD45RA, in a cohort of 28 women and 26 men (age range 19–110 years), including 11 long-living individuals (from >90 years old to<105 years old), and eight oldest centenarians (≥105 years old), all of them were previously analysed for Tαβ and NK cell immunophenotypes on the same blood sample collected on recruitment day. Naïve Vδ1 and Vδ2 cells showed an inverse relationship with age, particularly significant for Vδ1 cells. Terminally differentiated T subsets (TEMRA) were significantly increased in Vδ1 but not in Vδ2, with higher values observed in the oldest centenarians, although a great heterogeneity was observed. Both naïve and TEMRA Vδ1 and CD8+ Tαβ cell values from our previous study correlated highly significantly, which was not the case for CD4+ and Vδ2. Our findings on γδ TEMRA suggest that these changes are not unfavourable for centenarians, including the oldest ones, supporting the hypothesis that immune ageing should be considered as a differential adaptation rather than a general immune alteration. The increase in TEMRA Vδ1 and CD8+, as well as in NK, would represent immune mechanisms by which the oldest centenarians successfully adapt to a history of insults and achieve longevity. The aim of the present study was to investigate the impact of ageing on the blood levels of the two main Tγδ populations, including various subsets, in a cohort of 54 Sicilian individuals aged between 19 and 110 years (including eight semi- and supercentenarians). This cohort had previously been extensively studied for Tαβ and NK subsets. The results regarding Tγδ, when combined with the previous findings on Tαβ and NK, lend support to the idea that immune ageing should be regarded as a specific adaptation rather than a general immune alteration. In this context, the increase in TEMRA Vδ1 and CD8+ cells, along with NK CD3–CD56+CD16+, could represent immune mechanisms that enable the oldest centenarians to successfully adapt to a lifetime of antigenic challenges and achieve extreme longevity. Graphical Abstract [ABSTRACT FROM AUTHOR]

The adaptive and innate immune system is important in both initiating and preventing functional disorders during pregnancy, one of which is pre-eclampsia. The research aims to conduct the comparative quantification of selected subpopulations of peripheral blood immunoregulatory cells in pregnant women with pre-eclampsia in the third trimester. The marker receptors CD4, CD8, CD95, CD25, and CD27 and the marker antigen HLA-DR were considered. The screening was performed by flow cytometry with dual phenotyping using phycoerythrin- and fluorescein-isothiocyanate-labeled monoclonal antibodies. Data processing consisted in calculating a likelihood value to assess the statistical significance of the difference between the samples. A statistically significant decrease in the subpopulation titer of T and B lymphocytes with marker receptors CD4, CD8, and CD19 was found in pre-eclampsia patients. In the CD4 carrier T-lymphocyte population, there was an increased expression of the CD25/CD95 activation and apoptosis markers. In the CD8 T-killer population, a decreased representation of the CD27/CD25/CD95 markers of differentiation, activation, and apoptosis was deterministic. The expression pattern of the major histocompatibility complex antigen HLA-DR did not change significantly in normality and pathology. The titer of peripheral natural killer cells carrying the CD56 marker increased in patients with various degrees of disease severity, while the number of CD16 natural killer remained at the level of the control group. The research results suggest that a change in the ratio of the above receptors is a diagnostic indicator for pre-eclampsia. The research conducted a comparative analysis of specific immune cell subpopulations in the peripheral blood of pregnant women with pre-eclampsia during the third trimester. The study examined markers such as CD4, CD8, CD95, CD25, CD27, and HLA-DR using flow cytometry with dual phenotyping. The findings indicated a statistically significant decrease in the levels of T and B lymphocytes with CD4, CD8, and CD19 receptors in pre-eclampsia patients, along with altered expression patterns of activation and apoptosis markers in T lymphocytes, emphasizing the potential diagnostic value of these receptor ratios in pre-eclampsia. Graphical Abstract [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (SA) and its exotoxins activate eosinophils (Eos) and mast cells (MCs) via CD48, a GPI-anchored receptor belonging to the signaling lymphocytes activation molecules (SLAM) family. 2B4 (CD244), an immuno-regulatory transmembrane receptor also belonging to the SLAM family, is the high-affinity ligand for CD48. 2B4 is expressed on several leukocytes including NK cells, T cells, basophils, monocytes, dendritic cells (DCs), and Eos. In the Eos and MCs crosstalk carried out by physical and soluble interactions (named the 'allergic effector unit', AEU), 2B4–CD48 binding plays a central role. As CD48 and 2B4 share some structural characteristics and SA colonization accompanies most of the allergic diseases, we hypothesized that SA exotoxins (e.g. Staphylococcus enterotoxin B, SEB) can also bind and activate 2B4 and thereby possibly further aggravate inflammation. To check our hypothesis, we used in vitro, in silico, and in vivo methods. By enzyme-linked immunosorbent assay (ELISA), flow cytometry (FC), fluorescence microscopy, and microscale thermophoresis, we have shown that SEB can bind specifically to 2B4. By Eos short- and long-term activation assays, we confirmed the functionality of the SEB–2B4 interaction. Using computational modeling, we identified possible SEB-binding sites on human and mouse 2B4. Finally, in vivo, in an SEB-induced peritonitis model, 2B4-KO mice showed a significant reduction of inflammatory features compared with WT mice. Altogether, the results of this study confirm that 2B4 is an important receptor in SEB-mediated inflammation, and therefore a role is suggested for 2B4 in SA associated inflammatory conditions. In summary, we have shown a functional binding of SEB to cell surface expressed 2B4 in vitro , in silico , and in vivo. All these results strongly support the conclusion that 2B4 is an important receptor in SEB-mediated inflammation in allergy and beyond and therefore may constitute an interesting therapeutic target. Graphical Abstract [ABSTRACT FROM AUTHOR]

Early life is a time of increased susceptibility to infectious diseases and development of allergy. Innate lymphocytes are crucial components of the initiation and regulation of immune responses at mucosal surfaces, but functional differences in innate lymphocytes early in life are not fully described. We aimed to characterize the abundance and function of different innate lymphocyte cell populations in cord blood in comparison to that of adults. Blood was collected from adult donors and umbilical vessels at birth. Multicolor flow cytometry panels were used to identify and characterize lymphocyte populations and their capacity to produce hallmark cytokines. Lymphocytes were more abundant in cord blood compared to adults, however, mucosal-associated invariant T cells and natural killer T (NKT)-like cells, were far less abundant. The capacity of NKT-like cells to produce cytokines and their expression of the cytotoxic granule protein granzyme B and the marker of terminal differentiation CD57 were much lower in cord blood than in adults. In contrast, natural killer (NK) cells were as abundant in cord blood as in adults, they could produce IFNγ, and their expression of granzyme B was not significantly different from that of adult NK cells, although CD57 expression was lower. All innate lymphoid cell (ILC) subsets were more abundant in cord blood, and ILC1 and ILC2 were capable of production of IFNγ and IL-13, respectively. In conclusion, different innate lymphoid cells differ in both abundance and function in peripheral blood at birth and with important implications for immunity in early life. Innate lymphocytes may be important for immunity in early life. Natural killer T- (NKT-) and mucosal-associated invariant T-cells were found in low abundance in cord blood and NKT cells from cord blood were less capable of cytokine and granzyme B production than those from adults. In contrast, cord blood natural killer cells and subsets of innate lymphoid cells were abundant and capable of producing their hallmark cytokines. Graphical Abstract [ABSTRACT FROM AUTHOR]

Respiratory syncytial virus (RSV) infections are a major cause of bronchiolitis and pneumonia in infants and older adults, for which there is no known correlate of protection. Increasing evidence suggests that Fc-mediated antibody effector functions have an important role, but little is known about the development, heterogeneity, and durability of these functional responses. In light of future vaccine strategies, a clear view of the immunological background and differences between various target populations is of crucial importance. In this study, we have assessed both quantitative and qualitative aspects of RSV-specific serum antibodies, including IgG/IgA levels, IgG subclasses, antibody-dependent complement deposition, cellular phagocytosis, and NK cell activation (ADNKA). Samples were collected cross-sectionally in different age groups (11-, 24-, and 46-month-old children, adults, and older adults; n = 31–35 per group) and longitudinally following natural RSV infection in (older) adults (2–36 months post-infection; n = 10). We found that serum of 24-month-old children induces significantly lower ADNKA than the serum of adults (P < 0.01), which is not explained by antibody levels. Furthermore, in (older) adults we observed boosting of antibody levels and functionality at 2–3 months after RSV infection, except for ADNKA. The strongest decrease was subsequently observed within the first 9 months, after which levels remained relatively stable up to three years post-infection. Together, these data provide a comprehensive overview of the functional landscape of RSV-specific serum antibodies in the human population, highlighting that while antibodies reach adult levels already at a young age, ADNKA requires more time to fully develop. Serum antibodies of children aged 24- and 46-months induce lower RSV-specific antibody-dependent NK cell activation compared to (older) adults. In contrast, no difference is found in RSV-specific IgG levels, antibody-dependent cellular phagocytosis, and antibody-dependent complement deposition. [ABSTRACT FROM AUTHOR]

As the largest proportion of myeloid immune cells in tumors, macrophages play an important role in tumor growth and regression according to their different phenotypes, thus reprogramming macrophages has become a new research direction for cancer immunotherapy. Yeast-derived whole β-glucan particles (WGPs) can induce M0 macrophages to differentiate into M1 macrophages and convert M2 macrophages and tumor-associated macrophages (TAMs) into M1 macrophages. In vitro, studies have confirmed that WGP-treated macrophages increase the activating receptors in natural killer cells (NK cells) and enhance the cytotoxicity of NK cells. The extracellular regulated protein kinases (ERK) signaling pathway is involved in WGP-mediated regulation of the macrophage phenotype. Further in vivo studies show that oral WGP can significantly delay tumor growth, which is related to the increased proportion of macrophages and NK cells, the macrophage phenotype reversal, and the enhancement of NK cell immune function. NK-cell depletion reduces the therapeutic efficacy of WGP in tumor-bearing mice. These findings revealed that in addition to T cells, NK cells also participate in the antitumor process of WGP. It was confirmed that WGP regulates the macrophage phenotype to regulate NK-cell function. ERK1/2 signaling pathway involved in WGP regulation of macrophage phenotype. Macrophages polarized by WGP upregulate NK cell activity. NK cells participate in the antitumor effect of WGP. [ABSTRACT FROM AUTHOR]

Passive transfer of antithyroid antibodies in mice leads to reproductive disorders. The purpose was to assess the placental tissue of experimental animals under the influence of the circulating thyroperoxidase antibodies. We performed an immunohistochemical examination of murine placentae after a passive transfer of thyroperoxidase antibodies. Placentae of mice that passively transferred IgG from healthy donors were used as control samples. For histological examination, 30 placental samples were selected from mice from the anti-TPO group and 40 placental samples were taken from mice from the IgG group. Immunostaining for VEGFR1, THBS 1, Laminin, CD31, CD34, FGF-β, CD56, CD14, TNF-α, kisspeptin, MCL 1, and Annexin V was performed. There is a significant decrease in the relative area of the expression of VEGFR1 (23.42 ± 0.85 vs. 33.44 ± 0.35, P < 0.01), thrombospondin 1 (31.29 ± 0.83 vs. 34.51 ± 0.75, P < 0.01), CD14 (25.80 ± 0.57 vs. 32.07 ± 0.36, P <.01), CD56 (30.08 ± 0.90 vs. 34.92 ± 0.15, P < 0.01), kisspeptin (25.94 ± 0.47 vs. 31.27 ± 0.57, P < 0.01), MCL 1 (29.24 ± 1.06 vs. 38.57 ± 0.79, P < 0.01) in the labyrinth zone of the placentae of mice from the anti-TPO group compared with control group. A significant increase in the relative expression of laminin and FGF-β was noted in the group of mice to which antibodies to thyroperoxidase were transferred, compared with the control group (36.73 ± 1.38 vs. 29.83 ± 0.94, P < 0.01 and 23.26 ± 0.61 vs. 16.38 ± 1.01, P < 0.01respectively). Our study exposed an imbalance of pro- and anti-angiogenic factors, decreased representation of placental macrophages and NK cells, abnormal trophoblast invasion processes, and insufficient expression of antiapoptotic factors in the placentae of mice in which anti-TPO antibodies were passively transferred. We performed an immunohistochemical examination of murine placentae after a passive transfer of thyroperoxidase antibodies. Our study exposed an imbalance of pro- and anti-angiogenic factors, decreased representation of placental macrophages and NK cells, abnormal trophoblast invasion processes, and insufficient expression of antiapoptotic factors in the placentae of mice in which anti-TPO antibodies were passively transferred. [ABSTRACT FROM AUTHOR]

Summary: Mucosa-associated invariant T (MAIT) cells are evolutionarily conserved, innate-like T lymphocytes with enormous immunomodulatory potentials. Due to their strategic localization, their invariant T cell receptor (iTCR) specificity for major histocompatibility complex-related protein 1 (MR1) ligands of commensal and pathogenic bacterial origin, and their sensitivity to infection-elicited cytokines, MAIT cells are best known for their antimicrobial characteristics. However, they are thought to also play important parts in the contexts of cancer, autoimmunity, vaccine-induced immunity, and tissue repair. While cognate MR1 ligands and cytokine cues govern MAIT cell maturation, polarization, and peripheral activation, other signal transduction pathways, including those mediated by costimulatory interactions, regulate MAIT cell responses. Activated MAIT cells exhibit cytolytic activities and secrete potent inflammatory cytokines of their own, thus transregulating the biological behaviors of several other cell types, including dendritic cells, macrophages, natural killer cells, conventional T cells, and B cells, with significant implications in health and disease. Therefore, an in-depth understanding of how costimulatory pathways control MAIT cell responses may introduce new targets for optimized MR1/MAIT cell-based interventions. Herein, we compare and contrast MAIT cells and mainstream T cells for their expression of classic costimulatory molecules belonging to the immunoglobulin superfamily and the tumor necrosis factor (TNF)/TNF receptor superfamily, based not only on the available literature but also on our transcriptomic analyses. We discuss how these molecules participate in MAIT cells' development and activities. Finally, we introduce several pressing questions vis-à-vis MAIT cell costimulation and offer new directions for future research in this area. The CD40L-CD40 costimulatory axis modulates mucosa-associated invariant T (MAIT) cells' functions and mediates their bidirectional crosstalk with other important immunocytes. Activated MAIT cells rely on this pathway to promote dendritic cell maturation, resulting in type-I cytokine production as well as follicular helper T cell expansion in lymph nodes. In addition, CD40L signaling in MAIT cells enhances B cell activation and antibody responses. [ABSTRACT FROM AUTHOR]

Endometriosis is a common inflammatory disorder in women of reproductive age due to an abnormal endometrial immune environment and is associated with infertility. This study aimed to systematically understand the endometrial leukocyte types, inflammatory environment, and impaired receptivity at single-cell resolution. We profiled single-cell RNA transcriptomes of 138 057 endometrial cells from endometriosis patients (n = 6) and control (n = 7), respectively, using 10x Genomics platform. We found that one cluster of epithelial cells that expressed PAEP and CXCL14 was mostly from the control during the window of implantation (WOI). This epithelial cell type is absent in the eutopic endometrium during the secretory phase. The proportion of endometrial immune cells decreased in the secretory phase in the control group, whereas the cycle variation of total immune cells, NK cells, and T cells was absent in endometriosis. Endometrial immune cells secreted more IL-10 in the secretory phase than in the proliferative phase in the control group; the opposite trend was observed in endometriosis. Proinflammatory cytokines levels in the endometrial immune cells were higher in endometriosis than in the control group. Trajectory analysis revealed that the secretory phase epithelial cells decreased in endometriosis. Ligand–receptor analysis revealed that 11 ligand–receptor pairs were upregulated between endometrial immune and epithelial cells during WOI. These results provide new insights into the endometrial immune microenvironment and impaired endometrial receptivity in infertile women with minimal/mild endometriosis. We systematically revealed the eutopic endometrial single-cell transcriptome immune landscape in minimal/mild endometriosis and compared it with that of disease-free controls. Our study provides new insights into the eutopic endometrial inflammatory microenvironment and defective endometrial receptivity in patients with endometriosis-associated infertility. Our results give clues into immunopathogenesis of endometriosis endometriosis-associated infertility. [ABSTRACT FROM AUTHOR]

Summary: Natural killer (NK) cells possess the innate ability to eliminate cancerous cells effectively. Their crucial role in immunosurveillance has been widely recognized and exploited for therapeutic intervention. Despite the fast-acting nature of NK cells, NK adoptive cell transfer lacks favorable response in some patients. Patient NK cells often display diminished phenotype in preventing cancer progression resulting in poor prognosis. Tumor microenvironment plays a significant role in causing the downfall of NK cells in patients. The release of inhibitory factors by tumor microenvironment hinders normal function of NK cells against tumor. To overcome this challenge, therapeutic strategies such as cytokine stimulation and genetic manipulation are being investigated to improve NK tumor-killing capacity. One of the promising approaches includes generation of more competent NK cells via ex vivo cytokines activation and proliferation. Cytokine-induced ML-NK demonstrated phenotypic alterations such as enhanced expression of activating receptors which help elevate their antitumor response. Previous preclinical studies showed enhanced cytotoxicity and IFNγ production in ML-NK cells compared to normal NK cells against malignant cells. Similar effects are shown in clinical studies in which MK–NK demonstrated encouraging results in treating hematological cancer. However, there is still a lack of in-depth studies using ML-NK in treating different types of tumors and cancers. With convincing preliminary response, this cell-based approach could be used to complement other therapeutic modalities to achieve better clinical outcomes. The success of NK cells to eliminate tumors depends on their strong immunosurveillance capacity. Tumor microenvironment promotes the release of inhibitory factors which dampen NK cell functionality against tumor. This challenge can be overcome by transforming naïve NK cells to memory-like NK cells to enhance their ability to target tumors. [ABSTRACT FROM AUTHOR]

The effect of cytomegalovirus (CMV) infection on leukemia relapse and the potential mechanism remains controversial. In this retrospective study, we evaluated the association among CMV infection, NK reconstitution and clinical outcomes in consecutive patients with hematologic malignancy who underwent HLA matched sibling donor transplantation (MST). In total, 228 patients were enrolled in the study between January 2010 and December 2011. The cumulative incidence of CMV infection on day 100 post-HSCT was 13.6 ± 4.9%. The probabilities of OS and DFS were 45.4% vs. 71.7% (P = 0.004) and 43.9% vs. 64.2% (P = 0.050) in the patients with CMV infection and without CMV infection, respectively. The cumulative incidence of treatment-related mortality (TRM) and relapse at 5 years was 48.6 ± 9.6% vs. 11.5 ± 2.9% (P < 0.001) and 6.2 ± 4.3% vs. 29.2 ± 3.9% (P = 0.024) in the patients with CMV infection and without CMV infection, respectively. In the multivariate analysis, CMV infection was associated with higher TRM, lower OS, and lower DFS. In addition, we found that CMV infection may promote the recovery of the absolute number of NK cells and promote the differentiation of NK cells post-MST. In conclusion, CMV infection may promote the recovery and differentiation of NK cells and was correlated with a lower relapse rate post-MST. CMV infection associated with decreased relapse rate post MST. CMV infection associated with the recovery and differentiation of NK cells post MST. Rapid NK cells recovery and differentiation associated with decreased relapse post MST. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells are important anti-viral effector cells. The function and phenotype of the NK cells that constitute an individual's NK cell repertoire can be influenced by ongoing or previous viral infections. Indeed, infection with human cytomegalovirus (HCMV) drives the expansion of a highly differentiated NK cell population characterized by expression of CD57 and the activating NKG2C receptor. This NK cell population has also been noted to occur in HIV-1-infected individuals. We evaluated the NK cells of HIV-1-infected and HIV-1-uninfected individuals to determine the relative frequency of highly differentiated CD57+NKG2C+ NK cells and characterize these cells for their receptor expression and responsiveness to diverse stimuli. Highly differentiated CD57+NKG2C+ NK cells occurred at higher frequencies in HCMV-infected donors relative to HCMV-uninfected donors and were dramatically expanded in HIV-1/HCMV co-infected donors. The expanded CD57+NKG2C+ NK cell population in HIV-1-infected donors remained stable following antiretroviral therapy. CD57+NKG2C+ NK cells derived from HIV-1-infected individuals were robustly activated by antibody-dependent stimuli that contained anti-HIV-1 antibodies or therapeutic anti-CD20 antibody, and these NK cells mediated cytolysis through NKG2C. Lastly, CD57+NKG2C+ NK cells from HIV-1-infected donors were characterized by reduced expression of the inhibitory NKG2A receptor. The abundance of highly functional CD57+NKG2C+ NK cells in HIV-1-infected individuals raises the possibility that these NK cells could play a role in HIV-1 pathogenesis or serve as effector cells for therapeutic/cure strategies. Highly differentiated CD57+NKG2C+ natural killer (NK) cells are expanded during human cytomegalovirus (HCMV) infection. This expansion is exaggerated in individuals infected with both HCMV and HIV-1. Highly differentiated CD57+NKG2C+ NK cells have potential relevance for strategies to cure HIV-1 infection. [ABSTRACT FROM AUTHOR]

Sarcoma is a rare and heterogeneous class of mesenchymal malignancies with poor prognosis. Panobinostat (LBH589) as one of histone deacetylase (HDAC) inhibitors has demonstrated anti-tumor activity in patients with sarcoma, but its mechanisms remains unclear. Here, we found that LBH589 alone inhibited the proliferation and colony formation of soft tissue sarcoma (STS) cell lines. Transcriptome analysis showed that treatment with LBH589 augmented the NK cell-mediated cytotoxicity. Quantitative real-time PCR and flow cytometric analysis (FACS) further confirmed that LBH589 increased the expression of NKG2D ligands MICA/MICB. Mechanistically, LBH589 activated the Wnt/β-catenin pathway by upregulating the histone acetylation in β-catenin promoter. In vitro co-culture experiments and in vivo animal experiments showed that LBH589 increased the cytotoxicity of natural killer (NK) cells while Wnt/β-catenin inhibitor decreased the effects. Our findings suggest that LBH589 facilitates the anti-tumor effect of NK cells, highlights LBH589 an effective assistance drug in NK cell-based immunotherapies. [ABSTRACT FROM AUTHOR]

Systemic lupus erythematosus (SLE) is a multi-organ inflammatory disease with kidney inflammation, lupus nephritis (LN), being one of the most severe manifestations. Immune complex deposits, particularly in glomeruli, and T cells, B cells, and myeloid cells, mainly with extraglomerular localization, contribute to the inflammatory process. Natural killer (NK) cells have been suggested to play a role in autoimmune diseases, but have not been investigated in detail in renal lupus before. In this exploratory study, we performed the first characterization of NK cell number and distribution in LN kidney biopsies. Twelve SLE patients were analyzed in the active phase of disease and five patients following immunosuppressive therapy. CD56+ cells, corresponding to NK cells or NK-like T-cells, were identified in all patients; however, with reduced numbers in four out of five patients at follow-up. Furthermore, cells were present in the kidney interstitium and peri-glomerular areas, but only rarely in glomeruli. Fluorescent co-staining of CD56 or NKp46 and CD3 revealed the presence of both CD56+/NKp46+CD3-NK cells and CD56+/NKp46+CD3+NK-like T-cells. Compared to healthy kidney sections, one out of four LN patients showed increased numbers of NK cells. A correlation between CD56+ and NK cells with clinical parameters could not be observed, perhaps due to the small patient cohort. In conclusion, we have identified NK cells and NK-like T-cells in the LN kidney and performed the first detailed analysis of their localization during active and inactive diseases. Their role in LN pathogenesis is, however, unclear and deserves further studies. We perform the first characterization of number and distribution of NK cells and NK like T cells in renal tissue in the active phase of LN disease and following immunosuppressive treatment. [ABSTRACT FROM AUTHOR]

Mucosal-associated invariant T (MAIT) cells are a type of innate immune cells that protect against some infections. However, the involvement of MAIT cells in Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases (EBV-T/NK-LPD) is unclear. In this study, we found that MAIT cells were highly activated in the blood of patients with EBV-T/NK-LPD. MAIT cell activation levels correlated with disease severity and plasma IL-18 levels. Stimulation of healthy peripheral blood mononuclear cells with EBV resulted in activation of MAIT cells, and this activation level was enhanced by exogenous IL-18. MAIT cells stimulated by IL-18 might thus be involved in the immunopathogenesis of EBV-T/NK-LPD. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is the world's leading cause of tumor‐related mortalities. Natural killer (NK) cells play a critical role at the first immunological defense line against HCC initiation and progression. NK cell dysfunction is therefore an important mechanism for immune evasion of HCC cells. In the present study using a murine HCC model, we revealed the down‐regulation of PR/SET Domain 10 (PRDM10) in hepatic NK cells that were phenotypically and functionally exhausted. PRDM10 silencing diminished the expression of natural killer group 2 member D (NKG2D) and tumor necrosis factor (TNF)‐related apoptosis‐inducing ligand (TRAIL), augmented T cell immunoglobulin and ITIM domain (TIGIT) expression, and decreased the expression of interferon (IFN)‐γ, perforin and granzyme B in normal hepatic NK cells in vitro. Consistently, PRDM10‐deficient NK cells exhibited impaired cytotoxicity on target cells. In contrast, PRDM10 over‐expression promoted NKG2D and Fas ligand (FasL) expression, reduced CD96 expression and enhanced transcripts of IFN‐γ, perforin and granzyme B in NK cells in vivo. Moreover, PRDM10 silencing and PRDM10 over‐expression down‐regulated and up‐regulated Eomesodermin (Eomes) expression, respectively. In summary, this study reveals PRDM10 down‐regulation as a novel mechanism underlying NK cell dysfunction and identifies PRDM10 as a supporting factor of NK cell function. [ABSTRACT FROM AUTHOR]

Gamma‐tocotrienol (γT3) is an analogue of vitamin E with beneficial effects on the immune system, including immune‐modulatory properties. This study reports the immune‐modulatory effects of daily supplementation of γT3 on host T helper (Th) and T regulatory cell (Treg) populations in a syngeneic mouse model of breast cancer. Female BALB/c mice were fed with either γT3 or vehicle (soy oil) for 2 weeks via oral gavage before they were inoculated with syngeneic 4T1 mouse mammary cancer cells (4T1 cells). Supplementation continued until the mice were euthanized. Mice (n = 6) were euthanized at specified time‐points for various analysis (blood leucocyte, cytokine production and immunohistochemistry). Tumour volume was measured once every 7 days. Gene expression studies were carried out on tumour‐specific T lymphocytes isolated from splenic cultures. Supplementation with γT3 increased CD4+ (p < 0.05), CD8+ (p < 0.05) T‐cells and natural killer cells (p < 0.05) but suppressed Treg cells (p < 0.05) in peripheral blood when compared to animals fed with the vehicle. Higher interferon (IFN)‐γ and lower transforming growth factor (TGF)‐ꞵ levels were noted in the γT3 fed mice. Immunohistochemistry findings revealed higher infiltration of CD4+ cells, increased expression of interleukin‐12 receptor‐beta‐2 (IL‐12ꞵ2R), interleukin (IL)‐24 and reduced expression of cells that express the forkhead box P3 (FoxP3) in tumours from the γT3‐fed animals. Gene expression studies showed the down‐regulation of seven prominent genes in splenic CD4+ T cells isolated from γT3‐fed mice. Supplementation with γT3 from palm oil‐induced T cell‐dependent cell‐mediated immune responses and suppressed T cells in the tumour microenvironment in a syngeneic mouse model of breast cancer. [ABSTRACT FROM AUTHOR]

Numerous reports suggest that activating killer immunoglobulin‐like receptors (aKIRs) of natural killer (NK) cells, in addition to inhibitory KIRs (iKIRs), play a prognostic role after allogeneic haematopoietic stem cell transplantation (allo‐HSCT). We aimed to investigate the association between the dynamic expression of KIRs on NK cells and the outcomes, particularly regarding graft‐versus‐host disease (GvHD). This study retrospectively enrolled 260 pairs of donors and recipients who had undergone allo‐HSCT without in‐vitro T cell depletion. The mRNA transcription level of KIRs was determined by quantitative real‐time polymerase chain reaction (RT–qPCR). The levels of aKIR transcripts were decreased more than those of iKIRs during the occurrence of GvHD. The transcription levels of KIR2DS2 and KIR2DS4 in the patients developing GvHD, compared with those who were at a tolerance state, showed the most significant decrease in the month at their peak transcription levels (p = 0.03, p = 0.002). Significantly decreased expression of KIR2DS1 (p = 0.02), KIR2DS3 (p = 0.04) and KIR2DS5 (p = 0.04) in the GvHD group was observed when the transcription level reached a maximum. High expression of KIR3DS1 was associated with superior overall survival (OS) (p < 0.001). The expression of KIR2DS4 in the KIR genotype Bx group decreased more during GvHD, particularly at 3M (p = 0.02). These findings suggest that KIR genes are potential post‐HSCT biomarkers and dynamic changes in the KIR transcription levels can be detected to better predict the occurrence and evaluate the treatment of GvHD after transplantation. [ABSTRACT FROM AUTHOR]

Summary: Ageing dramatically affects number and function of both innate and adaptive arms of immune system, particularly T cell subsets, contributing to reduced vaccination efficacy, decreased resistance to infections and increased prevalence of cancer in older people. In the present paper, we analysed the age‐related changes in the absolute number of lymphocytes in 214 Sicilian subjects, and in the percentages of T and natural killer (NK) cells in a subcohort of donors. We compared these results with the immunophenotype of the oldest living Italian supercentenarian (aged 111 years). The results were also sorted by gender. The correlation between number/percentage of cells and age in all individuals. and separately in males and females, was examined using a simple linear regression analysis. We did not record the increase in the rate of inversion of the CD4/CD8 ratio, frequently reported as being associated with ageing in literature. Our observation was the direct consequence of a flat average trend of CD4+ and CD8+ T cell percentages in ageing donors, even when gender differences were included. Our results also suggest that CD4+ and CD8+ subsets are not affected equally by age comparing females with males, and we speculated that gender may affect the response to cytomegalovirus (CMV) infection. The supercentenarian showed a unique immunophenotypic signature regarding the relative percentages of her T cell subsets, with CD4+ and CD8+ T cell percentages and CD4+ naive T cell values in line with those recorded for the octogenarian subjects. This suggests that the supercentenarian has a naive 'younger' T cell profile comparable to that of a >80‐year‐old female. [ABSTRACT FROM AUTHOR]

Summary: The mechanisms that drive systemic lupus erythematosus (SLE) patients to achieve remission are unknown; one possible explanation might be T cell exhaustion. The aim of the present study was to measure CD4+ and CD8+ T cell exhaustion in SLE patients in prolonged remission (PR‐SLE) and compared them with patients with active SLE (Act‐SLE) and healthy subjects. We included 15 PR‐SLE patients, 15 Act‐SLE and 29 healthy subjects. T cell exhaustion was determined by flow cytometry according to the expression of programmed cell death 1 (PD)‐1, T cell immunoglobulin and mucin 3 (Tim‐3), natural killer cell receptor (2B4), eomesodermin (EOMES) and T‐box transcription factor TBX21 (T‐bet) in CD4+ and CD8+ T cells. Dimensionality reduction using the T‐distributed stochastic neighbor‐embedding algorithm and clustering analysis was used for the identification of relevant populations. Percentages of CD3+, CD4+ and CD8+ T cells were similar among groups. We identified five subpopulations of CD8+ and seven of CD4+ cells. The CD4+T‐bet+CD45RO+ cells identified in the unsupervised analysis were significantly increased in PR‐SLE versus Act‐SLE [median = 0·20, interquartile range (IQR) = 1·74–30·50 versus 1·68, IQR = 0·4–2·83; P < 0·01]. CD4+EOMES+ cells were also increased in PR‐SLE versus Act‐SLE (5·24, IQR = 3·38–14·70 versus 1·39, IQR = 0·48–2·87; P < 0·001). CD8+EOMES+ cells were increased in PR‐SLE versus Act‐SLE (37·6, IQR = 24·9–53·2 versus 8·13, IQR = 2·33–20·5; P < 0·001). Exhausted and activated T cells presented an increased frequency of PD‐1, CD57 and EOMES in SLE patients versus healthy subjects. Some subpopulations of T cells expressing markers associated with exhaustion are increased in patients in remission, supporting T cell exhaustion as a tolerance mechanism in SLE. Exhaustion of specific populations of T cells might represent a potential therapeutic tool that will contribute to the goal of achieving sustained remission in these patients. [ABSTRACT FROM AUTHOR]

Summary: Tuberculosis (TB) kills more people than any other single infectious disease globally. Despite decades of research, there is no vaccine to prevent TB transmission. Bacille Calmette–Guérin (BCG) vaccine, developed a century ago, is effective against childhood (disseminated and miliary) TB. However, its protective efficacy against pulmonary TB varies from 0 to 80% in different populations. One of the main reasons for the lack of an effective vaccine against TB is the lack of complete understanding about correlates of protective immunity on which to base vaccine design and development. However, some household contacts who are extensively exposed to Mtb infection remain persistently negative to tuberculin skin test and interferon‐gamma assay. These individuals, called 'resisters', clear Mtb infection early before the development of acquired immunity. The immunological basis of early Mtb clearance is yet to be established; however, innate lymphocytes such as monocytes/macrophages, dendritic cells, neutrophils and natural killer cells, and innate‐like T cells such as mucosal‐associated invariant T cells, invariant natural killer (NK) T cells and gamma‐delta (γδ) T cells, have been implicated in this early protection. In recent years, NK cells have attracted increasing attention because of their role in controlling Mtb infection. Emerging data from animal and epidemiological studies indicate that NK cells play a significant role in the fight against Mtb. NK cells express various surface markers to recognize and kill both Mtb and Mtb‐infected cells. This review presents recent advances in our understanding of NK cells in the fight against Mtb early during infection, with emphasis on cohort studies. [ABSTRACT FROM AUTHOR]

Summary: Vogt–Koyanagi–Harada (VKH) is an autoimmune disease characterized by inflammation in tissues that contain melanocytes. We aimed to increase the knowledge regarding immunological pathways deregulated in VKH disease. We compared the percentages of circulating natural killer (NK), NK T and T cells expressing the activatory markers: CD16, CD69, NK group 2D (NKG2D), natural cytotoxicity triggering receptor 3 (Nkp30), natural cytotoxicity triggering receptor 1 (Nkp46) and the inhibitory marker: NK group 2 member A (NKG2A) in 10 active VKH patients, 20 control subjects (CTR) and seven patients with Behçet disease (BD) by flow cytometry. Cytotoxic potential of NK cells was determined through the degranulation marker CD107a expression after contact with K562 cells by flow cytometry. Moreover, plasmatic levels of 27 cytokines were determined with a multiplex bead‐based assay. VKH patients showed higher percentages of NKG2Dpos NK and NK T cells versus CTR. The cytotoxic potential of NK cells induced by K562 cells was comparable between VKH patients and CTR. Finally, higher concentrations of interleukin (IL)‐4, IL‐5, IL‐7, IL‐17 and platelet‐derived growth factor‐subunits B (PDGF‐bb) were detected in plasma of VKH patients versus CTR. The immune profile of VKH patients was similar to that of BD patients. [ABSTRACT FROM AUTHOR]

Summary: Immune checkpoint therapy to reverse natural killer (NK) and T cell exhaustion has emerged as a promising treatment in various cancers. While anti‐programmed cell death 1 (PD‐1) pembrolizumab has recently gained Food and Drug Administration (FDA) approval for use in recurrent or metastatic cervical cancer, other checkpoint molecules, such as T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine‐based inhibition motif (ITIM) domains (TIGIT) and T cell immunoglobulin and mucin‐domain containing‐3 (Tim‐3), have yet to be fully explored in this disease. We report expression of TIGIT, Tim‐3 and PD‐1 on subsets of peripheral blood NK (CD56dim/negCD16bright/dim/neg and CD56brightCD16dim/neg) and T cells. The percentages of these cells were increased in women with cervical cancer and pre‐malignant lesions. PD‐1+ NK and T cells were likely to co‐express TIGIT and/or Tim‐3. These cells, with an apparently 'exhausted' phenotype, were augmented in patients. A subset of cells were also natural killer group 2 member D (NKG2D)‐ and DNAX accessory molecule 1 (DNAM‐1)‐positive. PD‐1int and PD‐1high T cells were notably increased in cervical cancer. Soluble programmed cell death ligand 1 (PD‐L1) was higher in cancer patient blood versus healthy donors and we observed a positive correlation between sPD‐L1 and PD‐1+ T cells in women with low‐grade lesions. Within the cancer group, there were no significant correlations between sPD‐L1 levels and cervical cancer stage. However, when comparing cancer versus healthy donors, we observed an inverse association between sPD‐L1 and total T cells and a correlation between sPD‐L1 and CD56dim NK cells. Our results may show an overview of the immune response towards pre‐cancerous lesions and cervical cancer, perhaps giving an early clue as to whom to administer blocking therapies. The increase of multiple checkpoint markers may aid in identifying patients uniquely responsive to combined antibody therapies. [ABSTRACT FROM AUTHOR]

Summary: Natural killer (NK) cell functions are regulated by diverse inhibitory and activating receptors, including killer cell immunoglobulin‐like receptors (KIR), which interact with human leukocyte antigen (HLA) class I molecules. Some KIR/HLA genetic combinations were reported associated with spontaneous clearance (SC) of hepatitis C virus (HCV) but with discordant results, possibly reflecting KIR and/or HLA gene polymorphism according to populations. KIR/HLA genetic combinations associated with both an exhaustive NK and T cell repertoire were investigated in a cohort of HIV–HCV co‐infected individuals with either SC (n = 68) or chronic infection (CI, n = 163) compared to uninfected blood donors [controls (Ctrl), n = 100]. Multivariate analysis showed that the HLA C2C2 environment was associated with SC only in European HIV–HCV co‐infected individuals [odds ratio (OR) = 4·30, 95% confidence interval = 1·57–12·25, P = 0·005]. KIR2D+ NK cell repertoire and potential of degranulation of KIR2DL1/S1+ NK cells were similar in the SC European cohort compared to uninfected individuals. In contrast, decreased frequencies of KIR2DS1+ and KIR2DL2+ NK cells were detected in the CI group of Europeans compared to SC and a decreased frequency of KIR2DL1/S1+ NK cells compared to controls. Regarding T cells, higher frequencies of DNAX accessory molecule‐1 (DNAM‐1)+ and CD57+ T cells were observed in SC in comparison to controls. Interestingly, SC subjects emphasized increased frequencies of KIR2DL2/L3/S2+ T cells compared to CI subjects. Our study underlines that the C2 environment may activate efficient KIR2DL1+ NK cells in a viral context and maintain a KIR2DL2/L3/S2+ mature T cell response in the absence of KIR2DL2 engagement with its cognate ligands in SC group of HCV–HIV co‐infected European patients. [ABSTRACT FROM AUTHOR]

Summary: Natural killer T (NKT) cells are an abundant subset of liver lymphocytes activated by lipid antigens presented on CD1d molecules that are expressed by cholangiocytes. We aimed to determine if bile from patients with chronic liver diseases contains antigenic lipids that can activate NKT cells. Using murine invariant (24.7, 24.8 and DN32.D3) and non‐invariant (14S.6, 14S.7 and 14S.10) NKT hybridomas we investigated the presence of lipid antigens in bile collected from the gallbladder of patients undergoing liver transplantation due to end‐stage liver disease. Biliary microbiota profiles were generated using 16S rRNA amplicon sequencing. We found that the patient bile samples contain antigens that activate both invariant and non‐invariant NKT hybridomas (24.7, 24.8, DN32.D3, 14S.6, 14S.7 and 14S.10), as demonstrated by activation of at least one hybridoma by eight of 10 bile samples. Activation at high dilutions suggests that some antigens are highly potent. We used the non‐invariant NKT hybridoma 14S.6 to screen 21 additional patient bile samples for NKT‐reactivity and demonstrated that 12 of 21 bile samples resulted in activation, three of which gave a strong activation. Four of 12 activating bile samples contained microbial DNA. Our results reveal an immunological pathway that could be of critical importance in biliary immunology. [ABSTRACT FROM AUTHOR]

Summary: Kawasaki disease (KD) is an acute pediatric vasculitis of unknown etiology that can cause coronary artery aneurysms, and is the leading cause of acquired heart disease in children. We studied aspects of the innate and adaptive immune response in 17 acute KD children prior to treatment with intravenous immunoglobulin. Distinct patterns within the innate immune response correlated with specific clinical features. Proinflammatory myeloid dendritic cells (mDC) were abundant in four of 17 (23·5%) subjects who were older and manifested severe inflammation with clinical myocarditis and elevated hepatobiliary enzyme levels. Of the nine subjects with low levels of anti‐inflammatory, tolerogenic mDC, six had enlarged cervical lymph nodes at diagnosis. In contrast, the adaptive immune repertoire varied greatly with no discernible patterns or associations with clinical features. Two subjects with aneurysms had numerous circulating CD8+ T cells. Ten subjects showed low CD4+ T cell numbers and seven subjects had CD4+ T cells in the normal range. CD4+ T cells expressed interleukin‐7 receptor (IL‐7R), suggesting repeated antigenic stimulation. Thymic‐derived regulatory T cells (nTreg) and peripherally induced regulatory T cells (iTreg) were also enumerated, with the majority having the nTreg phenotype. Natural killer (NK) and NK T cell numbers were similar across all subjects. Taken together, the results of the immune monitoring suggest that KD may have multiple triggers that stimulate different arms of the innate and adaptive compartment in KD patients. Thus, it is possible that diverse antigens may participate in the pathogenesis of KD. [ABSTRACT FROM AUTHOR]

Summary: Takayasu arteritis (TAK) is a large‐vessel granulomatous vasculitis; the inflammatory infiltration in arteries comprises macrophages, multi‐nucleated giant cells, CD4+ and CD8+ T cells, γδ T cells, natural killer (NK) cells and neutrophils. However, it is unknown which subtype of macrophages predominates. This study aims to evaluate macrophages subpopulations in the aorta in TAK. Immunohistochemistry was performed in the aorta from TAK patients (n = 22), patients with atherosclerotic disease (n = 9) and heart transplant donors (n = 8) using the markers CD68, CD86, CD206, CD3, CD20 and CD56. Active disease was observed in 54·5% of patients and active histological lesions were found in 40·9%. TAK patients presented atherosclerotic lesions in 27·3% of cases. The frequency of macrophages, M1 macrophages, T, B and NK cells was higher in the aorta from TAK and atherosclerotic patients compared to heart transplant donors. In TAK, macrophages and T cells were the most abundant cells in the aorta, and the expression of CD206 was higher than CD86 (P = 0·0007). No associations were found between the expression of cell markers and active disease or with atherosclerotic lesions. In TAK patients, histological disease activity led to higher T cell counts than chronic fibrotic lesions (P = 0.030), whereas prednisone use was associated with lower T cell counts (P = 0·035). In conclusion, M1 macrophages were more frequent in TAK and atherosclerotic patients compared to heart transplant donors, while M2 macrophages dominated M1 macrophages in TAK. T cells were associated with histological disease activity and with prednisone use in TAK. [ABSTRACT FROM AUTHOR]

Summary: A combination of pegylated interferon‐alpha (peg‐IFN‐α) and nucleos(t)ides analogue (NA) therapy can effectively reduce hepatitis B surface antigen (HBsAg), especially in NA‐experienced chronic hepatitis B (CHB) patients. However, the immune mechanism of this therapy is unclear. Forty NA‐experienced CHB patients were enrolled into this study. The frequencies of peripheral blood natural killer (NK) cells, dendritic cells (DCs), CD4+ T cells, CD8+ T cells, T helper (Th) cells, regulatory T cells (Treg), B cells and follicular T helper (Tfh) cells were evaluated by flow cytometry. Seven of the 40 patients converted to peg‐IFN‐α combined with NA treatment, while the other 33 continued to NA therapy. The decrease in HBsAg was more pronounced in the combination treatment group, and only patients receiving combination treatment achieved HBsAg loss. The frequency and absolute number of CD56bright NK cells in the combination treatment group increased significantly compared with the NA treatment group, whereas the CD56dim NK cells were decreased. In the NA treatment group, the proportions of CD4+ TN, CD8+ TN, CD19+ B and cytotoxic T lymphocyte antigen‐4 (CTLA‐4)+CD4+ T cells were increased, while the proportions of CD4+ TEM, CD8+ TEM, CD25+CD4+ Treg, CD25highCD4+ Treg, CD127lowCD25+ Treg, programmed cell death 1 (PD‐1)+CD4+ T, PD‐1+CD8+ T, CTLA‐4+CD8+ T, CCR4+CD25+ Treg and CCR4+CD25high Treg cells were decreased after therapy. For NA‐experienced CHB patients who achieved low HBsAg levels, combination treatment is more likely to result in HBsAg decline and HBsAg clearance by increasing the activity of CD56brightNK cells. [ABSTRACT FROM AUTHOR]

Summary: Natural killer (NK) cells are innate immune effectors which play a crucial role in recognizing and eliminating virally infected and cancerous cells. They effectively distinguish between healthy and distressed self through the integration of signals delivered by germline‐encoded activating and inhibitory cell surface receptors. The frequent up‐regulation of stress markers on genetically unstable cancer cells has prompted the development of novel immunotherapies that exploit such innate receptors. One prominent example entails the development of chimeric antigen receptors (CAR) that detect cell surface ligands bound by NK receptors, coupling this engagement to the delivery of tailored immune activating signals. Here, we review strategies to engineer CARs in which specificity is conferred by natural killer group 2D (NKG2D) or other NK receptor types. Multiple preclinical studies have demonstrated the remarkable ability of chimeric NK receptor‐targeted T cells and NK cells to effectively and specifically eliminate cancer cells and to reject established tumour burdens. Importantly, such systems act not only acutely but, in some cases, they also incite immunological memory. Moreover, CARs targeted with the NKG2D ligand binding domain have also been shown to disrupt the tumour microenvironment, through the targeting of suppressive T regulatory cells, myeloid‐derived suppressor cells and tumour vasculature. Collectively, these findings have led to the initiation of early‐phase clinical trials evaluating both autologous and allogeneic NKG2D‐targeted CAR T cells in the haematological and solid tumour settings. [ABSTRACT FROM AUTHOR]

Summary: Major histocompatibility complex class I (MHC‐I)‐dependent inhibitory receptors on natural killer (NK) cells have been found to contribute to NK cell dysfunction in hepatocellular carcinoma (HCC). However, the roles of MHC‐I‐independent inhibitory receptors on NK cells in HCC remain poorly defined. In this study, we analyzed the expression of the MHC‐I‐independent inhibitory receptors sialic acid‐binding immunoglobulin‐like lectin (Siglec)‐7 and Siglec‐9 on NK cells by analyzing the peripheral blood of 35 HCC patients and 63 healthy donors. We observed that HCC patients had lower frequencies and total numbers of NK cells in the peripheral blood. Importantly, both the expression levels of Siglec‐7 on NK cells and the frequencies of Siglec‐7+ NK cells were significantly reduced in HCC patients, which was accompanied by a decrease in activating receptor and an increase in inhibitory receptor expression on NK cells. Moreover, Siglec‐7+ NK cells expressed higher levels of activating receptors and displayed stronger effector functions, compared with Siglec‐7− NK cells. Our findings demonstrate for the first time that reduced Siglec‐7 expression predicts NK cell dysfunction in HCC patients, suggesting that Siglec‐7 may be a potential marker of functional NK cell subset in HCC patients. [ABSTRACT FROM AUTHOR]

Summary: Low‐dose interleukin (IL)‐2 has shown clinical benefits in patients with autoimmune and inflammatory diseases. Both regulatory T cells (Tregs) and natural killer (NK) cells are increased in response to low‐dose IL‐2 immunotherapy. The role of regulatory T cells in autoimmune diseases has been extensively studied; however, NK cells have not been as thoroughly explored. It has not been well reported whether the increase in NK cells is purely an epiphenomenon or carries actual benefits for patients with autoimmune diseases. We demonstrate that low‐dose IL‐2 expands the primary human CD56bright NK cells resulting in a contact‐dependent cell cycle arrest of effector T cells (Teffs) via retention of the cycle inhibitor p21. We further show that NK cells respond via IL‐2R‐β, which has been shown to be significant for immunity by regulating T cell expansion. Moreover, we demonstrate that blocking NK receptors NKp44 and NKp46 but not NKp30 could abrogate the regulation of proliferation associated with low‐dose IL‐2. The increase in NK cells was also accompanied by an increase in Treg cells, which is dependent on the presence of CD56bright NK cells. These results not only heighten the importance of NK cells in low‐dose IL‐2 therapy but also identify key human NK targets, which may provide further insights into the therapeutic mechanisms of low‐dose IL‐2 in autoimmunity. [ABSTRACT FROM AUTHOR]

Summary: Bile acids (BAs) are produced by liver hepatocytes and were recently shown to exert functions additional to their well‐known role in lipid digestion. As yet it is not known whether the mucosal‐associated invariant T (MAIT) cells, which represent 10–15% of the hepatic T cell population, are affected by BAs. The focus of the present investigation was on the association of BA serum concentration with MAIT cell function and inflammatory parameters as well as on the relationship of these parameters to body weight. Blood samples from 41 normal weight and 41 overweight children of the Lifestyle Immune System Allergy (LISA) study were analyzed with respect to MAIT cell surface and activation markers [CD107a, CD137, CD69, interferon (IFN)‐γ, tumor necrosis factor (TNF)‐α] after Escherichia coli stimulation, mRNA expression of promyelocytic leukemia zinc finger protein (PLZF) and major histocompatibility complex class I‐related gene protein (MR1), the inflammatory markers C‐reactive protein (CRP), interleukin (IL)‐8 and macrophage inflammatory protein (MIP)‐1α as well as the concentrations of 13 conjugated and unconjugated BAs. Higher body weight was associated with reduced MAIT cell activation and expression of natural killer cell marker (NKp80) and chemokine receptor (CXCR3). BA concentrations were positively associated with the inflammatory parameters CRP, IL‐8 and MIP‐1α, but were negatively associated with the number of activated MAIT cells and the MAIT cell transcription factor PLZF. These relationships were exclusively found with conjugated BAs. BA‐mediated inhibition of MAIT cell activation was confirmed in vitro. Thus, conjugated BAs have the capacity to modulate the balance between pro‐ and anti‐inflammatory immune responses. [ABSTRACT FROM AUTHOR]

Summary: T cell immunoglobulin and ITIM domain (TIGIT) is an inhibitory receptor expressed on lymphocytes that was recently propelled under the spotlight as a major emerging target in cancer immunotherapy. TIGIT interacts with CD155 expressed on antigen‐presenting cells or tumour cells to down‐regulate T cell and natural killer (NK) cell functions. TIGIT has emerged as a key inhibitor of anti‐tumour responses that can hinder multiple steps of the cancer immunity cycle. Pre‐clinical studies indicated that TIGIT blockade may protect against various solid and haematological cancers. Several monoclonal antibodies (mAbs) that block the inhibitory activity of human TIGIT have been developed. Clinical trials are ongoing, investigating TIGIT blockade as a monotherapy or in combination with anti‐PD1/PD‐L1 mAbs for the treatment of patients with advanced solid malignancies. In this review, we cover our current knowledge on TIGIT, from its discovery in 2009 to its current status as a clinical target. [ABSTRACT FROM AUTHOR]

Summary: Glioblastoma (GBM) is an aggressive cancer with a very poor prognosis. Generally viewed as weakly immunogenic, GBM responds poorly to current immunotherapies. To understand this problem more clearly we used a combination of natural killer (NK) cell functional assays together with gene and protein expression profiling to define the NK cell response to GBM and explore immunosuppression in the GBM microenvironment. In addition, we used transcriptome data from patient cohorts to classify GBM according to immunological profiles. We show that glioma stem‐like cells, a source of post‐treatment tumour recurrence, express multiple immunomodulatory cell surface molecules and are targeted in preference to normal neural progenitor cells by natural killer (NK) cells ex vivo. In contrast, GBM‐infiltrating NK cells express reduced levels of activation receptors within the tumour microenvironment, with hallmarks of transforming growth factor (TGF)‐β‐mediated inhibition. This NK cell inhibition is accompanied by expression of multiple immune checkpoint molecules on T cells. Single‐cell transcriptomics demonstrated that both tumour and haematopoietic‐derived cells in GBM express multiple, diverse mediators of immune evasion. Despite this, immunome analysis across a patient cohort identifies a spectrum of immunological activity in GBM, with active immunity marked by co‐expression of immune effector molecules and feedback inhibitory mechanisms. Our data show that GBM is recognized by the immune system but that anti‐tumour immunity is restrained by multiple immunosuppressive pathways, some of which operate in the healthy brain. The presence of immune activity in a subset of patients suggests that these patients will more probably benefit from combination immunotherapies directed against multiple immunosuppressive pathways. [ABSTRACT FROM AUTHOR]

Summary: A20, a pivotal anti‐inflammatory protein, preserves immune homeostasis and regulates prolonged inflammation. A previous study has shown that A20 expression levels are down‐regulated in peripheral blood mononuclear cells (PBMCs) from patients with ankylosing spondylitis (AS). However, the precise role of A20 in reducing autoimmune disorders needs to be further elucidated. In this study, A20 expression was found to be preferentially reduced on circulating CD56bright natural killer (NK) cells in patients with AS, and its level was negatively correlated with that of proinflammatory cytokines. Further investigation demonstrated that A20 reduces interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α production in CD56bright NK cells after stimulation with monokines or phorbol myristate acetate (PMA)/ionomycin(P/I). Furthermore, CD56bright NK cells isolated from AS patients promote TNF‐α secretion by autologous monocytes, and increasing the A20 expression level partially attenuates this process. More importantly, decreased A20 expression on circulating CD56bright NK cells is associated with worse disease status in patients with AS. Our findings reveal that A20 participates in the pathogenesis of AS by negatively regulating CD56bright NK cells and that its reduced expression contributes to a worsened disease status in patients with AS. [ABSTRACT FROM AUTHOR]

Summary: Type 1 diabetes (T1D) results from autoimmune destruction of insulin‐producing beta cells in pancreatic islets. Various immune cell populations are involved in disease development and natural course. However, to our knowledge, so far there are no comprehensive comparative investigations of all main immune cell populations and their most important subsets at the onset of disease. Therefore, in the current study, we analyzed 51 peripheral blood immune cell populations in 22 young T1D patients and in 25 age‐matched controls using a comprehensive polychromatic flow cytometry panel developed for whole blood by the COST Action no. BM0907 ENTIRE (European Network for Translational Immunology Research and Education: From Immunomonitoring to Personalized Immunotherapy) consortium. We found that in T1D patients, frequencies and absolute counts of natural killer (NK) cells, dendritic cells (DC) and T cells, as well as their respective subsets, were significantly altered compared to controls. Further, we observed that changes in several cell populations (e.g. CD14+CD16+ non‐classical monocytes, plasmablasts) were dependent on the age of the patient. In addition to age‐related changes, we also found that alterations in immune cell patterns were associated with parameters such as the presence of ketoacidosis and C‐peptide serum levels. Our study provides a foundation for future studies investigating different cell lineages and their role in T1D and illustrates the value of polychromatic flow cytometry for evaluating all main peripheral immune cells and their subsets in whole blood samples. [ABSTRACT FROM AUTHOR]

Summary: The major histocompatibility complex (MHC) class I‐related chain A (MICA) is induced upon stress, and labels malfunctioning cells for their recognition by cytotoxic lymphocytes. Alterations in this recognition and also abnormal natural killer (NK) functions have been found in systemic lupus erythematosus (SLE). MICA can be shed from cells, subsequently acting as a soluble decoy receptor (sMICA). Our purpose was to study circulating sMICA levels in relationship with the activation of innate pathways in PBMC in a cohort of lupus patients. NK cells were characterized by flow cytometry. Gene expression of Toll‐like receptors (TLR), interferon (IFN)‐I sensitive genes and MICA were separately analyzed in monocytes, T cells and B cells. Serum sMICA was measured with enzyme‐linked immunosorbent assay (ELISA). In our cohort, NK cell counts dropped in relationship with disease activity. sMICA showed an inverse trend with NK cell counts, as well as a significant association with activity indices, but not with complement decrease. Levels of sMICA associated to proteinuria and active nephritis. A multivariate regression model revealed anti‐nuclear antibody (ANA) titres, the up‐regulation of TLR‐4 in T cells and lower vitamin D as predictors of sMICA enhancement. Interestingly, vitamin D showed an inverse association with proteinuria and a strong correlation with T cell MICA mRNA levels. According to our data, circulating sMICA identifies a subgroup of lupus patients with low vitamin D, innate activation of T cells and nephritis. We propose that lymphocyte shedding could account for the enhancement of sMICA and reflect an immune evasion mechanism driving disease activation in lupus. [ABSTRACT FROM AUTHOR]

Summary: Viruses, when used as vectors for vaccine antigen delivery, can induce strong cellular and humoral responses against target epitopes. Recent work by Hansen et al. describes the use of a cytomegalovirus‐vectored vaccine, which is able to generate a stable effector‐memory T cell population at the sites of vaccination in rhesus macaques. This vaccine, targeted towards multiple epitopes in simian immunodeficiency virus (SIV), did not induce classical CD8+ T cells. However, non‐canonical CD8+ T cell induction occurred via major histocompatibility complex (MHC) class II and MHC‐E. The MHC‐E‐restricted T cells could recognize broad epitopes across the SIV peptides, and conferred protection against viral challenge to 55% of vaccinated macaques. The human homologue, human leucocyte antigen (HLA)‐E, is now being targeted as a new avenue for vaccine development. In humans, HLA‐E is an unusually oligomorphic class Ib MHC molecule, in comparison to highly polymorphic MHC class Ia. Whereas MHC class Ia presents peptides derived from pathogens to T cells, HLA‐E classically binds defined leader peptides from class Ia MHC peptides and down‐regulates NK cell cytolytic activity when presented on the cell surface. HLA‐E can also restrict non‐canonical CD8+ T cells during natural infection with various pathogens, although the extent to which they are involved in pathogen control is mostly unknown. In this review, an overview is provided of HLA‐E and its ability to interact with NK cells and non‐canonical T cells. Also discussed are the unforeseen beneficial effects of vaccination, including trained immunity of NK cells from bacille Calmette–Guérin (BCG) vaccination, and the broad restriction of non‐canonical CD8+ T cells by cytomegalovirus (CMV)‐vectored vaccines in pre‐clinical trials. [ABSTRACT FROM AUTHOR]

Summary: Systemic lupus erythematosus (SLE) is a complex autoimmune disorder whose pathology involves multiple immune cell types, including B and T lymphocytes as well as myeloid cells. While it is clear that autoantibody‐producing B cells, as well as CD4+ T cell help, are key contributors to disease, little is known regarding the role of innate lymphoid cells such as natural killer (NK) cells in the pathogenesis of SLE. We have characterized the phenotype of NK cells by multi‐color flow cytometry in a large cohort of SLE patients. While the overall percentage of NK cells was similar or slightly decreased compared to healthy controls, a subset of patients displayed a high frequency of NK cells expressing the proliferation marker, Ki67, which was not found in healthy donors. Although expression of Ki67 on NK cells correlated with Ki67 on other immune cell subsets, the frequency of Ki67 on NK cells was considerably higher. Increased frequencies of Ki67+ NK cells correlated strongly with clinical severity and active nephritis and was also related to low NK cell numbers, but not overall leukopenia. Proteomic and functional data indicate that the cytokine interleukin‐15 promotes the induction of Ki67 on NK cells. These results suggest a role for NK cells in regulating the immune‐mediated pathology of SLE as well as reveal a possible target for therapeutic intervention. [ABSTRACT FROM AUTHOR]

Summary: Immunosuppression therapies including corticosteroids fail to prevent bronchiolitis obliterans syndrome (BOS), primarily a disease of the small airways, following lung transplantation. We reported increases in steroid‐resistant proinflammatory lymphocytes and their loss of histone deacetylase 2 (HDAC2), an important mediator of steroid action, in the blood of stable lung transplant recipients. We noted similar increases in the steroid‐resistant lymphocytes in both the blood and small airways in BOS compared with the large airways. We hypothesized that these small airway cells would also exhibit a loss of HDAC2, and that these changes could be reversed by treatment with theophylline (HDAC2 activator). Blood, bronchoalveolar lavage and large and small airway brushings were collected from lung transplant patients with BOS (n = 12) or stable lung function (n = 18) and healthy aged‐matched controls (n = 13). Intracellular proinflammatory cytokines [interferon (IFN‐γ) and tumour necrosis factor (TNF)‐α and HDAC2 were measured in CD8+ T, natural killer (NK) T‐like and NK cells from cultured small airway brushings ± 5 mg/l theophylline ± 1 µM prednisolone using flow cytometry. Increased small airway CD8 T, NK T‐like and NK cells were identified in BOS versus stable transplant and controls. In BOS, these cells exhibited increased IFN‐γ/TNF‐α and a loss of HDAC2. HDAC2 expression by small airway CD8+ T cells correlated with forced expiratory volume in 1 s (FEV1) (R = 0·880, P = 0·031). Theophylline and prednisolone synergistically up‐regulated HDAC2 in CD8+ T cells. BOS is associated with loss of HDAC2 from steroid‐resistant proinflammatory CD8+ T, NK T‐like and NK cells in the small airways. Therapeutically increasing HDAC2 in these lymphocytes may reduce steroid resistance and improve graft survival. Immunosuppression therapies including corticosteroids fail to prevent bronchiolitis obliterans syndrome (BOS), primarily a disease of the small airways, following lung transplantation. We report that BOS is associated with loss of HDAC2 from steroid‐resistant proinflammatory CD8+ T, NKT‐like and NK cells in the small airways. Therapeutically increasing HDAC2 in these lymphocytes may reduce steroid resistance and improve graft survival. [ABSTRACT FROM AUTHOR]

Summary: Cytomegalovirus (CMV) infection is a potentially fatal complication in patients receiving haematopoietic stem cell transplantation (HSCT), but recent evidence indicates that CMV has strong anti‐leukaemia effects due in part to shifts in the composition of natural killer (NK) cell subsets. NK cells are the primary mediators of the anti‐leukaemia effect of allogeneic HSCT, and infusion of allogeneic NK cells has shown promise as a means of inducing remission and preventing relapse of several different haematological malignancies. The effectiveness of these treatments is limited, however, when tumours express human leucocyte antigen (HLA)‐E, a ligand for the inhibitory receptor NKG2A, which is expressed by the vast majority of post‐transplant reconstituted and ex‐vivo expanded NK cells. It is possible to enhance NK cell cytotoxicity against HLA‐Epos malignancies by increasing the proportion of NK cells expressing NKG2C (the activating receptor for HLA‐E) and lacking the corresponding inhibitory receptor NKG2A. The proportion of NKG2Cpos/NKG2Aneg NK cells is typically low in healthy adults, but it can be increased by CMV infection or ex‐vivo expansion of NK cells using HLA‐E‐transfected feeder cells and interleukin (IL)‐15. In this review, we will discuss the role of CMV‐driven NKG2Cpos/NKG2Aneg NK cell expansion on anti‐tumour cytotoxicity and disease progression in the context of haematological malignancies, and explore the possibility of harnessing NKG2Cpos/NKG2Aneg NK cells for cancer immunotherapy. [ABSTRACT FROM AUTHOR]

Summary: Patients with recurrent miscarriage (RM) show up‐regulated cytotoxic natural killer (NK) cells that are suspected to play a causal role in abortion. In the present study, we investigated counter‐regulating inhibitory mechanisms and compared the results in RM patients with those of healthy controls (HC), patients with end‐stage renal disease (ESRD) and kidney transplant recipients late post‐transplant (TX). NK, NK T and T cell subsets were analysed in the peripheral blood of 31 RM, 14 female ESRD and nine female TX patients as well as 21 female HC using eight‐colour fluorescence flow cytometry. Compared with HC, RM patients showed significantly higher absolute numbers of CD56+ NK cells co‐expressing the phenotype interferon (IFN)‐γR+, IL‐4+, transforming growth factor (TGF)‐β+, IL‐4+ human leucocyte antigen D‐related (HLA‐DR)+, TGF‐β+HLA‐DR+, IL‐4+TGF‐β+, IL‐4+TGF‐β–, IFN‐γ+ and/or IL‐10–IFN‐γ+ (all P ≤ 0·01), more IL‐17+CD56bright (P = 0·028) NK cells and more CD56dimCD16+ NK cells co‐expressing IFN‐γR, IFN‐γ, IL‐4 and/or TGF‐β (all P ≤ 0·01). When the same cell subsets were analysed in ESRD or TX patients, cytokine‐producing NK cell subsets were not significantly different from those of HC. RM patients showed significantly higher absolute numbers of CD158a+, CD158b+, CD158a–CD158e+ (all P < 0·05), NKG2D+NKG2A+, NKG2D +NKG2A–, NKG2D+ and/or NKG2A+ (all P ≤ 0·01) CD56+ NK cells and higher CD158a+, CD158b+ (all P < 0·05), NKG2D+ and/or NKG2A+ (all P < 0·01) CD56dim+CD16+ NK cells than HC. In contrast, ESRD patients had normal and TX recipients had lower CD158a+ and NKG2D+NKG2A–CD56+ NK cells and lower CD158a+CD56dim+CD16+ NK cells (all P < 0·05) than HC. RM patients have abnormally high circulating NK cells expressing inhibitory cytokines and inhibitory surface receptors which might contribute to the pathogenesis of RM. [ABSTRACT FROM AUTHOR]

Summary: Regulatory B (Breg) cells are characterized by various membrane markers and the secretion of different inhibitory cytokines. A new subset of Breg cells was identified as CD5hi Fas‐ligand (FasL)hi. Their main reported role is to suppress anti‐viral and anti‐tumour immune responses, and, hence they have been dubbed ‘killer’ B cells. In this study, we aim to assess the role of these cells in chronic hepatitis C virus (HCV) infection, and determine if they contribute to the increased viral load and persistence of HCV and its related autoimmunity. (i) FasL expression on CD5hi B cells is increased significantly in HCV‐infected patients compared to healthy individuals [28·06 ± 6·71 mean fluorescence intensity (MFI) ± standard error of the mean (s.e.m.), median = 27·9 versus 10·87 ± 3·97 MFI ± s.e.m., median = 10·3, respectively, P <  0·0001]. (ii) Killer B cells from HCV patients increased autologous CD4+ T cell apoptosis compared to the apoptosis in healthy individuals [39·17% ± 7·18% mean ± standard deviation (s.d.), median = 39·6 versus 25·92 ± 8·65%, mean ± s.d., median = 24·1%, P <  0·0001, respectively]. A similar increase was observed in CD8+ T cell apoptosis (54·67 ± 15·49% mean ± s.d., median = 57·3 versus 21·07% ± 7·4%, mean ± s.d., median = 20%, P = 0·0006, respectively). (iii) By neutralizing FasL with monoclonal anti‐FasL antibodies, we have shown that the induction of apoptosis by killer B cells is FasL‐dependent. (iv) Increased expression of FasL on CD5hi B cells is correlated positively with an increased viral load and the presence of anti‐nuclear antibodies and rheumatoid factor in HCV. This is the first study in which killer B cells have been suggested to play a pathogenic role in HCV. They seem to be involved in HCV's ability to escape efficient immune responses. [ABSTRACT FROM AUTHOR]

Summary: All organisms are exposed constantly to a variety of infectious and injurious stimuli. These induce inflammatory responses tailored to the threat posed. While the innate immune system is the front line of response to each stimulant, it has been considered traditionally to lack memory, acting in a generic fashion until the adaptive immune arm can take over. This outmoded simplification of the roles of innate and acquired arms of the immune system has been challenged by evidence of myeloid cells altering their response to subsequent encounters based on earlier exposure. This concept of ‘innate immune memory’ has been known for nearly a century, and is accepted among myeloid biologists. In recent years other innate immune cells, such as natural killer cells, have been shown to display memory, suggesting that innate immune memory is a trait common to several cell types. During the last 30 years, evidence has slowly accumulated in favour of not only haematopoietic cells, but also stromal cells, being imbued with memory following inflammatory episodes. A recent publication showing this also to be true in epithelial cells suggests innate immune memory to be widespread, if under‐appreciated, in non‐haematopoietic cells. In this review, we will examine the evidence supporting the existence of innate immune memory in stromal cells. We will also discuss the ramifications of memory in long‐lived tissue‐resident cells. Finally, we will pose questions we feel to be important in the understanding of these forgotten cells in the field of innate memory. [ABSTRACT FROM AUTHOR]

Summary: Natural killer (NK) cells play a major role in host immunity against leukaemia and lymphoma. However, clinical trials applying NK cells have not been as efficient as hoped for. Patients treated with rapidly accelerated fibrosarcoma (RAF) inhibitors exhibit increased tumour infiltration by immune cells, suggesting that a combination of RAF inhibitors with immunotherapy might be beneficial. As mitogen‐activated protein kinases (MAPKs) such as raf‐1 proto‐oncogene, serine/threonine kinase (CRAF) regulate NK cell functions, we performed an in‐vitro investigation on the potential of clinically relevant short‐acting tyrosine kinase inhibitors (TKIs) as potential adjuvants for NK cell therapy: NK cells from healthy human blood donors were thus treated with sorafenib, sunitinib or the pan‐RAF inhibitor ZM336372 during ex‐vivo expansion. Functional outcomes assessed after washout of the drugs included cytokine production, degranulation, cytotoxicity, apoptosis induction and signal transduction with/without target cell contact. Paradoxically, sorafenib enhanced NK cell effector functions in a time‐ and dose‐dependent manner by raising the steady‐state activation level. Of note, this did not lead to NK cell exhaustion, but enhanced activity against target cells such as K562 or Daudis mediated via the RAS/RAF/extracellular‐regulated kinase (ERK) pathway, but not via protein kinase B (AKT). Our data will pave the path to develop a rationale for the considered use of RAF inhibitors such as sorafenib for pre‐activation in NK cell‐based adoptive immune therapy. [ABSTRACT FROM AUTHOR]