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Summary Current donor cell-dependent strategies can only produce limited “made-to-order” therapeutic natural killer (NK) cells for limited patients. To provide unlimited “off-the-shelf” NK cells that serve many recipients, we designed and demonstrated a holistic manufacturing scheme to mass-produce NK cells from induced pluripotent stem cells (iPSCs). Starting with a highly accessible human cell source, peripheral blood cells (PBCs), we derived a good manufacturing practice-compatible iPSC source, PBC-derived iPSCs (PBC-iPSCs) for this purpose. Through our original protocol that excludes CD34+ cell enrichment and spin embryoid body formation, high-purity functional and expandable NK cells were generated from PBC-iPSCs. Above all, most of these NK cells expressed no killer cell immunoglobulin-like receptors (KIRs), which renders them unrestricted by recipients' human leukocyte antigen genotypes. Hence, we have established a practical “from blood cell to stem cells and back with less (less KIRs)” strategy to generate abundant “universal” NK cells from PBC-iPSCs for a wide range of patients., Highlights • A GMP-compatible iPSC source has been generated from peripheral blood cells • An industry-friendly protocol has been developed to produce NK cells from iPSCs • These iPSC-derived NK cells are high-purity, functional, and KIR negative • These iPSC-derived NK cells recognize and kill a wide variety of cancer cells, To provide unlimited “off-the-shelf” NK cells that serve many recipients, Zeng and colleagues demonstrate a manufacturing scheme to mass-produce NK cells from peripheral blood cell-derived iPSCs (PBC-iPSCs). Through their original protocol, high-purity functional NK cells are generated from PBC-iPSCs. Most of these NK cells express no killer cell immunoglobulin-like receptors, which renders them unrestricted by recipients' HLA genotypes.

Summary Interleukin 21 (IL-21) plays key roles in humoral immunity and autoimmune diseases. It is known to function in mature CD4 + T follicular B cell helper (T FH ) cells, but its potential involvement in early T cell ontogeny is unclear. Here, we find that a significant population of newly activated thymic and peripheral CD4 + T cells functionally expresses IL-21 soon after birth. This naturally occurring population, termed natural (n)T H 21 cells, exhibits considerable similarity to mature T FH cells. nT H 21 cells originating and activated in the thymus are strictly dependent on autoimmune regulator (AIRE) and express high levels of NUR77, consistent with a bias toward self-reactivity. Their activation/expansion in the periphery requires gut microbiota and is held in check by FoxP3 + T REG cells. nT H 21 cells are the major thymic and peripheral populations of IL-21 + cells to expand in an IL-21-dependent humoral autoimmune disease. These studies link IL-21 to T cell ontogeny, self-reactivity, and humoral autoimmunity.

Summary The interaction of mesenchymal stromal cells (MSCs) with natural killer (NK) cells is traditionally thought of as a static inhibitory model, whereby resting MSCs inhibit NK cell effector function. Here, we use a dynamic in vitro system of poly(I:C) stimulation to model the interaction of NK cells and tissue-resident MSCs in the context of infection or tissue injury. The experiments suggest a time-dependent system of regulation and feedback, where, at early time points, activated MSCs secrete type I interferon to enhance NK cell effector function, while at later time points TGF-β and IL-6 limit NK cell effector function and terminate inflammatory responses by induction of a regulatory senescent-like NK cell phenotype. Importantly, feedback of these regulatory NK cells to MSCs promotes survival, proliferation, and pro-angiogenic properties. Our data provide additional insight into the interaction of stromal cells and innate immune cells and suggest a model of time-dependent MSC polarization and licensing., Graphical Abstract, Highlights • Poly(I:C) activation of tissue-resident MSC leads to a time-dependent polarization • MSC early inflammatory response, via IFN-α/β, activates NK cells • MSC late regulatory response induces senescent-like NK cells via TGF-β and IL-6 • Senescent-like NK cell feedback to MSCs promotes survival and pro-angiogenic activity, Brandau et al. stimulated MSCs of the nasal mucosa with poly(I:C), a compound which mimics viral RNA. Although resting MSCs are thought to inhibit NK cell function, stimulated MSCs exerted a time-dependent biphasic response, which either promoted NK cell effector function (early response) or induced a senescent-like process (late response). The data suggest a model of time-dependent MSC polarization and innate immune interaction.

Summary HLA haplotype-homozygous (HLA-homo) induced pluripotent stem cells (iPSCs) are being prepared to be used for allogeneic transplantation of regenerated tissue into recipients carrying an identical haplotype in one of the alleles (HLA-hetero). However, it remains unaddressed whether natural killer (NK) cells respond to these regenerated cells. HLA-C allotypes, known to serve as major ligands for inhibitory receptors of NK cells, can be classified into group 1 (C1) and group 2 (C2), based on their binding specificities. We found that the T cells and vascular endothelial cells regenerated from HLA-homo-C1/C1 iPSCs were killed by specific NK cell subsets from a putative HLA-hetero-C1/C2 recipient. Such cytotoxicity was canceled when target cells were regenerated from iPSCs transduced with the C2 gene identical to the recipient. These results clarify that NK cells can kill regenerated cells by sensing the lack of HLA-C expression and further provide the basis for an approach to prevent such NK cell-mediated rejection responses., Graphical Abstract, Highlights • Cells from HLA-homo iPSCs are killed by NK cells from an HLA-hetero C1/C2 individual • NK cells kill the regenerated cells by sensing the lack of KIR ligand expression • Cytotoxicity is cancelled when regenerated cells overexpress the missing KIR ligand, In this article, Kawamoto and colleagues show that NK cells derived from an HLA-hetero individual killed the cells regenerated from HLA-homo iPSCs in KIR ligand-mismatched cases, by sensing the lack of KIR ligand expression. Such cytotoxicity was cancelled when regenerated cells are enforced to express the missing KIR ligand, providing a novel approach to prevent NK cell-mediated rejection.

IL-4 is a cytokine commonly secreted by TH2 and follicular helper T (TFH) cells after antigenic sensitization. TH2 cells have been thought to be the major contributor of B cell help as a source of IL-4 responsible for class switch recombination to Immunoglobulin G1 (IgG1) and Immunoglobulin E (IgE). Importantly, there are some differences in transcriptional regulation between these two T cell subsets. The IL-4 production by TH2 and TFH cells is distinctively regulated by two pathways, GATA-3-mediated Il4-HS2 enhancer and Notch mediated Il4-CNS-2 enhancer. IgE and IgG1 antibody responses are mainly controlled by IL-4-secreting TFH cells, but not by TH2 cells. In this review, we discuss the role of TH2 and TFH cells in IgE production and allergic responses.

Considering umbilical cord blood (UCB) as a rich source of hematopoietic stem cells, we introduced a cost-effective approach to expand CD3depleted UCB-MNCs into functional NK cells. CD3depleted UCB-MNCs were expanded in the presence or absence of a feeder [bone marrow stem cells (BMSCs) or osteoblasts], with or without cytokines and their differentiation into NK cells was determined by flow cytometry. NK cell function was quantified by LAMP-1/CD107a expression, TNF-α/IFN-γ release, and LDH release/PI staining in targets. Higher expansion of NK cells was observed after two weeks in the presence of BMSCs and cytokines (104 ± 15) compared to osteoblasts and cytokines (84 ± 29, p

Human natural killer (NK) cells are considered professional cytotoxic cells that are integrated into the effector branch of innate immunity during antiviral and antitumoral responses. The purpose of this study was to examine the peripheral distribution and expression of NK cell activation receptors from the fresh peripheral blood mononuclear cells of 30 breast cancer patients prior to any form of treatment (including surgery, chemotherapy, and radiotherapy), 10 benign breast pathology patients, and 24 control individuals. CD3−CD56dimCD16bright NK cells (CD56dim NK) and CD3−CD56brightCD16dim/− NK cells (CD56bright NK) were identified using flow cytometry. The circulating counts of CD56dim and CD56bright NK cells were not significantly different between the groups evaluated, nor were the counts of other leukocyte subsets between the breast cancer patients and benign breast pathology patients. However, in CD56dim NK cells, NKp44 expression was higher in breast cancer patients (P = .0302), whereas NKp30 (P = .0005), NKp46 (P = .0298), and NKG2D (P = .0005) expression was lower with respect to healthy donors. In CD56bright NK cells, NKp30 (P = .0007), NKp46 (P = .0012), and NKG2D (P = .0069) expression was lower in breast cancer patients compared with control group. Only NKG2D in CD56bright NK cells (P = .0208) and CD56dim NK cells (P = .0439) showed difference between benign breast pathology and breast cancer patients. Collectively, the current study showed phenotypic alterations in activation receptors on CD56dim and CD56bright NK cells, suggesting that breast cancer patients have decreased NK cell cytotoxicity.

Natural killer (NK) cell-associated lymphoproliferative disorder includes NK/T cell lymphoma, nasal type and aggressive NK cell leukemia which exhibit poor outcomes. However, benign NK cell proliferative lesion has been recognized in the gastrointestinal tract under the name of NK-cell enteropathy or lymphomatoid gastropathy. We report a case of a similar CD56-positive NK-cell proliferative disorder involving the gallbladder and gastrointestinal tract in a 33-year-old woman who presented with chronic cholecystitis and underwent cholecystectomy. The gallbladder showed a few scattered polyps which were infiltrated by medium-sized atypical lymphoid cells with eosinophilic cytoplasmic granules. On immunohistochemistry, the lymphoid cells were positive for CD2, CD56, T-cell-restricted intracellular antigen-1, and granzyme B, but negative for CD3, CD4, CD5, CD8, CD20, CD30, CD34, CD68 and myeloperoxidase. In situ hybridization for Epstein–Barr virus-encoded RNA was negative and T-cell receptor gene rearrangement was polyclonal. The patient is under close observation for 36months without any evidence of lymphoma.

We describe a cohort of 50 elderly subjects, age at least 70 years. We present gender-specific findings in T lymphocyte markers and soluble immune mediators. We show the correlation between cytomegalovirus infection status with CD56dim NK cell responses to a variety of stimuli and with CD56bright/CD56dim NK cell ratio. We also present the correlation of retinol binding protein (RBP)−4 plasma levels with NK cell responses and we explore the relationship between gender and adiponectin, 25(OH)D (vitamin D), and RBP4 in affecting CD56dim NK cell responses. These data are discussed in Al-Attar et al. (2016) [1]. Keywords: NK cell, Ageing, Cytomegalovirus, T cell, Sex factors, Vitamin D, C-reactive protein, Adiponectin, IL-15, Sphingosine-1-phosphate, Retinol binding protein-4

Human papillomavirus type 16 (HPV16) infections are intra-epithelial, and thus, HPV16 is known to interact with Langerhans cells (LCs), the resident epithelial antigen-presenting cells (APCs). The current paradigm for APC-mediated induction of T cell anergy is through delivery of T cell receptor signals via peptides on MHC molecules (signal 1), but without costimulation (signal 2). We previously demonstrated that LCs exposed to HPV16 in vitro present HPV antigens to T cells without costimulation, but it remained uncertain if such T cells would remain ignorant, become anergic, or in the case of CD4+ T cells, differentiate into Tregs. Here we demonstrate that Tregs were not induced by LCs presenting only signal 1, and through a series of in vitro immunizations show that CD8+ T cells receiving signal 1+2 from LCs weeks after consistently receiving signal 1 are capable of robust effector functions. Importantly, this indicates that T cells are not tolerized but instead remain ignorant to HPV, and are activated given the proper signals. Keywords: T cell anergy, T cell ignorance, Immune tolerance, Human papillomavirus, HPV16, Langerhans cells

The thymus is the principal organ responsible for supporting the generation and maturation of T cells from hematopoietic progenitor cells arriving from the bone marrow. Thymocytes undergo a series of well-defined differentiation steps that lead to the generation of T-cell receptor bearing mature T cells.

Background β-Lactam hypersensitivity has been classified according to the phenotype and function of drug-specific T cells. However, new T-cell subsets have not been considered. Objective The objective of this study was to use piperacillin as a model of β-lactam hypersensitivity to study the nature of the drug-specific T-cell response induced in the blood and skin of hypersensitive patients and healthy volunteers. Methods Drug-specific T cells were cloned from blood and inflamed skin, and cellular phenotype and function were explored. Naive T cells from healthy volunteers were primed to piperacillin, cloned, and subjected to the similar analyses. Results PBMC and T-cell clones (n = 570, 84% CD4 + ) from blood of piperacillin-hypersensitive patients proliferated and secreted T H 1/T H 2 cytokines alongside IL-22 after drug stimulation. IL-17A secretion was not detected. Drug-specific clones from inflamed skin (n = 96, 83% CD4 + ) secreted a similar profile of cytokines but displayed greater cytolytic activity, secreting perforin, granzyme B, and Fas ligand when activated. Blood- and skin-derived clones expressed high levels of skin-homing chemokine receptors and migrated in the presence of the ligands CCL17 and CCL27. Piperacillin-primed naive T cells from healthy volunteers also secreted IFN-γ, IL-13, IL-22, and cytolytic molecules. Aryl hydrocarbon receptor blockade prevented differentiation of the naive T cells into antigen-specific IL-22–secreting cells. Conclusion Together, our results reveal that circulating and skin-resident, antigen-specific, IL-22–secreting T cells are detectable in patients with β-lactam hypersensitivity. Furthermore, differentiation of naive T cells into antigen-specific T H 22 cells is dependent on aryl hydrocarbon receptor signaling.

Natural killer (NK) cells are a group of innate immune cells. They show spontaneous cytolytic activity against cells under stress or infected with a virus. NK cells show a wide tissue distribution and a variable phenotype from tissue to tissue. Unlike adaptive immune cells, the cytolytic function of NK cells does not require clonal expansion. The function of NK cells is regulated by a cumulative signal received from the activating and inhibitory receptors. Mostly, expression of inhibitory receptors is controlled by genetic factors and provides tolerance to the self-tissues, whereas activation of receptor expression is controlled by environmental factors, and helps to mount the effector immune response against virus infection and tumor. NK cells isolated from the peripheral blood show antitumor cytolytic activity, which has led to several clinical trials using NK cells as adoptive cellular therapy which, however, have showed very limited success. With the advancement of or knowledge about NK cell biology, a combination of modified NK cells or NK cells in combination with other therapeutics showed better clinical output. In this review, we discuss the development of NK cells in humans and mice, various NK cell subsets and tissue distribution, an interaction of NK cells with other innate immune cells and adaptive immune cells, and the mechanism of NK cell-mediated antitumor immunity. We further discuss the use of NK cells to control tumor growth and suggested possible ways to improve the NK cell-based therapy.

We have previously reported on the deregulation of cellular microRNAs involved in hematopoiesis and inflammation in human T-cell lymphotropic virus type 1 (HTLV-I)–transformed cells. In this study, we demonstrate that miR-150 and miR-223 specifically target the signal transducer and activator of transcription 1 (STAT1) 3′ untranslated region, reducing STAT1 expression and dampening STAT1-dependent signaling in human T cells. The effects of miR-150 and miR-223 on endogenous STAT1 were confirmed using inducible cell lines. Our studies also showed that miR-150 expression is upregulated by interleukin-2 signaling in adult T cell leukemia/lymphoma (ATL) cells. HTLV-I–transformed and ATL-derived cells have reduced levels of miR150 and miR223 expression, which coincide with increased STAT1 expression and STAT1-dependent signaling. Knockdown of STAT1 by short hairpin RNA demonstrated that the constitutive activation of STAT1 is required for the continuous proliferation of HTLV-I–transformed cells. Our studies further demonstrate that increased expression of STAT1 in ATL cells is associated with higher levels of major histocompatibility complex class I expression. Previous studies have demonstrated that the pressure exerted by natural killer (NK) cells in vivo can edit leukemic tumor cells by forcing an increased expression of major histocompatibility complex class I to escape immune clearance. STAT1-expressing tumor cells produce more aggressive tumors because they cannot be eliminated by NK cells. Our results suggest that therapeutic approaches using combined targeting of STAT1 and MHC class I may be an effective approach to activate NK cell–mediated clearance of ATL tumor cells.

γδ T cells constitute the third arm of a tripartite adaptive immune system in jawed vertebrates, besides αβ T cells and B cells. Like the other two lymphocyte-types, they express diverse antigen receptors, capable of specific ligand recognition. Functionally, γδ T cells represent a system of differentiated subsets, sometimes engaged in cross-regulation, which ultimately determines their effect on other components of the immune system, including B cells and antibodies. γδ T cells are capable of providing help to B cells in antibody production. More recently it became clear that γδ T cells influence B cell differentiation during the peripheral stages of B cell development, control levels of circulating immunoglobulin (all subclasses), and affect production of autoantibodies. Because of this relationship between γδ T cells and B cells, the extensive variation of γδ T cells among human individuals might be expected to modulate their humoral responsiveness.

The A2b receptor (A2bR) belongs to the adenosine receptor family. Emerging evidence suggest that A2bR is implicated in tumor progression in some murine tumor models, but the therapeutic potential of targeting A2bR in melanoma has not been examined. This study first shows that melanoma-bearing mice treated with Bay 60-6583, a selective A2bR agonist, had increased melanoma growth. This effect was associated with higher levels of immune regulatory mediators interleukin-10 (IL-10) and monocyte chemoattractant protein 1 (MCP-1) and accumulation of tumor-associated CD11b positive Gr1 positive cells (CD11b+Gr1+) myeloid-derived suppressor cells (MDSCs). Depletion of CD11b+Gr1+ cells completely reversed the protumor activity of Bay 60-6583. Conversely, pharmacological blockade of A2bR with PSB1115 reversed immune suppression in the tumor microenvironment, leading to a significant melanoma growth delay. PSB1115 treatment reduced both levels of IL-10 and MCP-1 and CD11b+Gr1+ cell number in melanoma lesions. These effects were associated with higher frequency of tumor-infiltrating CD8 positive (CD8+) T cells and natural killer T (NKT) cells and increased levels of T helper 1 (Th1)-like cytokines. Adoptive transfer of CD11b+Gr1+ cells abrogated the antitumor activity of PSB1115. These data suggest that the antitumor activity of PSB1115 relies on its ability to lower accumulation of tumor-infiltrating MDSCs and restore an efficient antitumor T cell response. The antitumor effect of PSB1115 was not observed in melanoma-bearing nude mice. Furthermore, PSB1115 enhanced the antitumor efficacy of dacarbazine. These data indicate that A2bR antagonists such as PSB1115 should be investigated as adjuvants in the treatment of melanoma.

Group 1 innate lymphoid cells (ILCs) include natural killer (NK) cells and ILC1. NK cells function in response to intracellular pathogens such as viruses and they directly kill infected cells as well as produce cytokines that activate innate and adaptive components of the immune response. While the critical functions of ILC1 are still under investigation, these cells share many features with NK cells including expression of a common core of transcription factors and a requirement for the T-box binding factors for their development. In this article I will discuss the essential features of NK cell and ILC1 development, and I will discuss the transcription factors that are known to be critical for their development from their common ancestor, the common lymphoid progenitor.

Research on the pathogenesis of multiple sclerosis (MS) has almost exclusively been conducted on T cells, more specifically CD4+ T cells. This has been based on the theory that the most effective genetic factor in MS disease is located within the major histocompatibility complex class II region. This region plays a vital and central role in the development and maturation of cell tolerance. The other reason was accessibility of experimental autoimmune encephalomyelitis, an animal model for MS. This murine model can readily be produced by injecting encephalitogenic myelin-specific T cells. The general consensus was that B cells participate in autoimmune disease pathogenesis only through production of autoantibodies. However, we now know that the role of B cells goes beyond an antibody-producing factory; they are the major antigen-presenting cells (APCs), and they produce both pro-inflammatory and anti-inflammatory cytokines in the vicinity of the affected region. Therefore, when an autoantigen-specific B cell is present, it will be the first APC to take the self-protein, break it down, and present it to T cells, priming them to become activated cells, in effect jump-starting the autoreactive chain.

Natural Killer (NK) cells are effector cells of the innate immune system and are important in the control of viral infection. Several key NK cell receptors have been associated with differential human immunodeficiency virus type 1 (HIV-1) disease progression and/or transmission. Moreover, HIV-1 has evolved multiple mechanisms to evade NK cell recognition, implying that NK cells can contribute to the control of HIV-1 infection. Within the past decade, our understanding of the interplay between NK cell immunity and HIV-1 pathogenesis has significantly expanded. This article summarizes the current knowledge pertaining to the role of NK cells in HIV-1 infection.

Nectin and nectin-like molecules (necls) are important regulators of intercellular junctions and tissue morphogenesis. In addition, several members from this family exert immunoregulatory functions by their interactions with receptors expressed at the cell surface of immune cells. These receptors binding nectin and necls proteins include DNAM-1 (CD226, TLiSA-1, PTA1), CD96 (TACTILE), TIGIT (WUCAM, VSTM3), and CRTAM and were shown to impact the functions of diverse immune cell types including natural killer (NK) cells, monocytes, dendritic cells (DCs), and T lymphocytes. In this article, we will review the most recent knowledge concerning the biochemistry and the signaling of these receptors. We will discuss their specific role in the biology of NK cells, antigen-presenting cells, and T lymphocytes. In addition, we will examine the pathological implication of these receptors and their potential therapeutic application in cancer, infectious disease, and autoimmunity.

Natural killer (NK) cells are classically considered innate immune effector cells involved in the first line of defense against infection and malignant cells of the body. More recently, NK cells have been discovered to share similarities with adaptive T lymphocytes, such as long-lasting antigen-specific responses to secondary challenges. NK cells are able to distinguish healthy cells from abnormal cells due to low or absent expression of MHC class I molecules in combination with activating ligands on virus-infected and cancer cells. Overall, the threshold for NK cell attack is regulated by the net input of activating and inhibitory signals perceived from target cells. In the cancer microenvironment, however, NK cells frequently become functionally impaired by inhibitory factors produced by immunosuppressive immune cells and cancer cells. In this article, we outline the regulation of NK cell cytolytic activity leading to cancer cell destruction or tumor cell escape. Evidence for a role of NK cells in cancer immunosurveillance is discussed. Finally, we present recent approaches which focus on exploiting NK cell anticancer responses for immunotherapeutic approaches.

T lymphocytes expressing the CD4 marker have diverse functions within the immune system. A subset of CD4 T lymphocytes known as T-helper (Th) cells is essential in the generation and augmentation of humoral immune responses and cell-mediated immunity. Other subsets of CD4 T cells known as T regulatory cells have an opposite function and will be described in a different article. Here we review the important role of CD4 Th cells in antitumor immunity in providing help for the generation of antibodies and CD8 cytotoxic T-lymphocytes capable of limiting tumor cell growth. Furthermore, CD4 Th cells are essential for generating memory CD8 T cells, which are responsible for preventing tumor recurrences. In addition to their intrinsic helper function, some tumor-reactive CD4 Th cells can also serve as effector cells promoting tumor eradication via production of cytostatic cytokines within the tumor microenvironment or through cell-mediated cytotoxicity. Due to their important role in antitumor responses, effective immunotherapy approaches such as antitumor vaccines include strategies to generate tumor-reactive CD4 Th cell responses.

Multiple sclerosis (MS) is a progressive demyelinating disease associated with chronic inflammation in the central nervous system (CNS). Genetic linkage is found in genes related to T cell function, and T cell infiltration is evident in MS lesions, suggesting a pathophysiological role for these cells. In the MS animal model experimental autoimmune encephalomyelitis (EAE), activated CD4+ and CD8+ T cells that recognize CNS antigens can induce MS-like symptoms. Various cytokines from these T cells trigger inflammation, critically contributing to the pathogenesis of the CNS disease. Evidence suggests an important role for cytokine-mediated crosstalk between T cells and nonimmune cells, including endothelial cells, glial cells, and fibroblasts in enhancing CNS inflammation. Counterbalancing T cell-induced inflammation, certain regulatory CD4+ and CD8+ T cell subsets can suppress CNS disease progression. Here, we discuss the pathophysiological role of T cells during MS and EAE, including neuro–immune interactions that allow T cells to invade the CNS.

Despite decades of intense research, new functions for CD4 T cells in immunity to viral and other infections are revealed each year, suggesting that some are still unknown. Defense against viral infection includes a mosaic of multiple, highly specialized responses that often synergize to clear virus. Moreover, the development of subsets of CD4 effector T cells with diverse functions is determined by the detailed characteristics of the particular infection so that the exact composition and kinetics of a response to a given virus are unique. As virus is cleared, a population of memory CD4 T cells mirroring the diversity of the effectors is generated, again strongly influenced by the status of the viral infection during the effector phase of the CD4 T cell response. When there is a new viral challenge, the effectiveness of CD4 T cell immunity depends on the subsets composing the memory pool. Thus development of more effective vaccines that harness the potential of CD4 T cell immunity requires a detailed understanding of the full complexity of the CD4 T cell response and how it is regulated.

Th17 cells are a subset of effector CD4 T cells that induce neutrophilic tissue inflammation, particularly in mucosal tissues. While they play a critical role in host defense against extracellular bacteria and fungi, they also have been implicated in the pathogenesis of a number of T cell–mediated autoimmune disorders, including multiple sclerosis, rheumatoid arthritis, and psoriasis. Consistent with their dichotomous roles in promoting host defense and inducing autoimmunity, several subtypes of Th17 cells have been described with distinct effector functions and differing ability to induce autoimmune tissue inflammation. Moreover, Th17 cells are markedly plastic, both in their expression of cytokines typically associated with other effector T cell subsets and in their relationship with regulatory CD4 T cells; and this plasticity has important functional consequences. In this article, we describe the mechanisms that control Th17 cell differentiation, function, and plasticity, as well as highlight Th22 cells, a recently described and closely related CD4 T cell subset.

Natural killer (NK) cells demonstrate potent activity against a variety of viruses. The most important features of the antiviral response include NK cell activation, cytotoxic and cytokine-mediated effector functions, and interaction with other immune cells. The mechanisms utilized by NK cells to sense and respond to infection have been characterized in both humans and mice. In this article, we review our current understanding of how NK cells contribute to antiviral defenses.

The immune response to tuberculosis is a complex event consisting of various elements of innate immunity which, if not effective, are then followed by the generation of acquired specific cell-mediated immunity. The latter consists of the interaction of antigen-specific T cells with infected macrophages and is driven by the interleukin-12/gamma interferon cytokine axis (IL-12/IFNγ), a process that is the paradigm of ‘Th1 immunity’ to intracellular bacterial parasites. In parallel, the host recruits large numbers of macrophages and other cells into a containment structure – the granuloma – the formation of which is controlled by a large array of chemokines and their receptors. As these processes contain the infection, the effector T cell response contracts and is replaced by memory T cells, most of which express an effector memory T cell phenotype. Other T cell subsets are also involved, including IL-17–secreting CD4 + T cells (Th17), and Foxp3 + CD4 + regulatory T cells. The interrelationship between these three primary CD4 + responses in the pathogenesis of the disease is still unclear, and further complicated by the observation that regulatory T cells are potently induced by high virulence strains of the bacterium and appear to interfere with vaccination processes. Overall, while the major components of acquired immunity to tuberculosis have been delineated, there is still much to learn.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Although the precise etiology of MS remains unclear, CD4 + T cells have been proposed to play not only effector but also regulatory roles in MS. CD4 + T cells can be divided into four subsets: pro-inflammatory helper T (Th) 1 and Th17 cells, anti-inflammatory Th2 cells and regulatory T cells (Tregs). The roles of CD4 + T cells in MS have been clarified by either “loss-of-function” or “gain-of-function” methods, which have been carried out mainly in autoimmune and viral models of MS: experimental autoimmune encephalomyelitis and Theiler's murine encephalomyelitis virus infection, respectively. Observations in MS patients were consistent with the mechanisms found in the MS models, that is, increased pro-inflammatory Th1 and Th17 activity is associated with disease exacerbation, while anti-inflammatory Th2 cells and Tregs appear to play a protective role.

γδ T cells form an integral part of the immune system of various lymphoid and mucosal tissues in mice and humans. Recently, it has become apparent that unlike αβ T cell receptor (TCR)-bearing T cells, these innate-like lymphocytes undergo functional programming during their development in the fetal and adult thymus. Distributed throughout the body, γδ T cells act as first responders to various environmental and pathogenic perturbations. Therefore, understanding the development and functional programming of these γδ T cells has broad implications on health and disease. Here, we review a complex network of molecular mechanisms that govern the cellular processes involved in γδ T cell development and concurrent installation of IFNγ and IL-17 effector programs, including TCR signaling strength, genetic and epigenetic programs, E protein activity, and various microenvironmental factors.

Diverse forms of cellular stress activate signaling pathways controlling the expression of molecules with key roles in immunity, which allows the recognition of stressed cells and tissues by components of the innate and adaptive immune systems. For instance, triggering of ataxia telangiectasia mutated (ATM) or p53 pathways is known to stimulate the expression of ligands of activating receptors of natural killer (NK) cells, such as NK group 2, member D (NKG2D) or DNAX accessory molecule-1 (DNAM-1), hence inducing cytotoxic immune responses against stressed cells. Likewise, immunogenic death of stressed cancer cells frequently involves the exposure of calreticulin at the cell surface, which enhances the recruitment of dendritic cells and, eventually, the activation of T cell-mediated responses. In this chapter, we summarize the major molecular mechanisms underpinning the modulation of the immunosurveillance against stressed cells and tissues.

Natural killer (NK) cells have the capacity to regulate acute and persistent viral infections, the development of long-term immunological memory, and even autoimmunity by virtue of their control of CD4 and CD8 T cells. This NK cell control of T cells can involve a variety of distinct mechanisms, including NK cell–mediated lysis of the T cells or their antigen-presenting cells or by NK cell–produced immunoregulatory cytokines like IL-10. We show here that a variety of distinct NK cell receptor–ligand interactions may be involved in this process and that the expression of these receptors and ligands may vary with the inflammatory stimulus.

CD8 T cells play a pivotal role in our defense against viruses and intracellular bacteria. A productive CD8 T cell response requires the generation of a large number of effector cells in order to clear the infection. Most of these cells will die following the clearance of a pathogen, while a small fraction of them will survive and mature into long-lived memory cells that provide enhanced protection against future encounters with the same pathogen. What determines the eventual fate of these effector CD8 T cells has been a long-standing question. In this article, we summarize recent advances in understanding how pathogen-specific CD8 T cells transition from the effector to memory phase by focusing on the identification of effector and memory precursors, the models that help to explain this differentiation process, and the cytokine signaling and genetic pathways that influence these cell fate decisions.

T follicular helper (Tfh) cells are a specialized subset of CD4 + T cells that support B cell responses in germinal centers (GC). Tfh development is initiated when antigen-presenting cells provide signals that trigger differentiation toward the Tfh state through the induction of key transcription factors such as B cell lymphoma-6 (Bcl-6). The Tfh differentiation program establishes a chemokine profile that causes Tfh-precursors cells to migrate to the border between the T zone and the B cell follicle where they interact with activated B cells. As a result of these interactions there is stabilization and commitment of Tfh-precursor cells to the Tfh lineage. Within the GC, Tfh cells provide growth and survival signals to GC B cells that have enhanced affinity for antigen as a result of somatic mutation of their B cell receptors. Tfh cells help in mediating the survival of GC B cells and subsequent differentiation into long-lived antibody-producing plasma and memory B cells that confer long-term immunity against their specific-antigen.

Natural killer (NK) cells are a member of the innate lymphoid cell (ILC) family that provide host defense against tumors and pathogen-infected cells. They express a remarkably diverse repertoire of inhibitory and activating receptors on their cell surface, which regulates their immune responses. As their name implies, NK cells can kill transformed or infected cells by the release of perforin and granzymes or by using effector molecules of the tumor necrosis factor (TNF) family, such as TNF, TNF-related apoptosis inducing ligand (TRAIL), and Fas ligand, which induce apoptosis in the target cells. Additionally, upon activation NK cells rapidly produce chemokines and cytokines, including interferon (IFN)-γ, GM-CSF, and IL-10, that recruit and affect the function of hematopoietic and nonhematopoietic cells in the host.

In paraneoplastic neurological syndromes associated with Hu-antibodies (Hu-PNS) an important role for cellular immunity is hypothesized. We characterized the cerebrospinal fluid (CSF) pleocytosis in Hu-PNS patients by assessing the major lymphocyte subsets by flow cytometry. The B cell subset in the CSF of Hu-PNS patients showed a significant absolute (similar to 20x) and relative (similar to 3x) expansion, while the numbers of CD4+ T cells, CD8+ T cells and NK cells only showed an absolute expansion (similar to 4-7x) compared to the controls. On the other hand, the NKT cell subset showed a significant relative reduction in CSF and in blood of Hu-PNS patients. The relative B cell expansion is consistent with the intrathecal synthesis of Hu-antibodies, while the increased number of T and NK cells supports an additional role for cellular immunity in the pathogenesis of Hu-PNS. In addition, the autoimmune hypothesis of Hu-PNS is supported by the relative NKT cell deficiency. (C) 2008 Elsevier B.V. All rights reserved.

Hepatitis B surface antigen (HBsAg)-specific T cells were analysed in 16 healthy individuals vaccinated against hepatitis B, using optimised protocols. HBsAg-specific IFN-gamma producing CD4(+) T cells were found at a similar low frequency (0.01%) within the naive T cell subset, the central and the effector memory T cell subset. Overall, HBsAg-specific total CD4(+) T cells were detected in approximately 81% of the HBV vaccinees. The use of dendritic cells substantially increased the otherwise low proliferative responses but not the percentage of IFN-gamma producing cells. The analysis of readily detectable CMV-specific CD4(+) T cell responses was used as a positive control and confirmed the adequacy of our assays. T cell responses associated with (in-) adequate hepatitis B vaccination can now be analysed in more detail. (C) 2007 Elsevier B.V. All rights reserved.

Regulatory T (Treg) cells are considered to inhibit the development of both type 1 (Th1) and type 2 helper T (Th2) cells. However, it is recently reported that there are reduced numbers of Treg cells in patients with allergic diseases as compared with individuals who have high levels of serum immunoglobulin E and blood eosinophils but are asymptomatic. Therefore, Treg cells may suppress the onset of allergic disease by down-regulating other types of immune cells besides Th1 and Th2 cells. The newly discovered interleukin 17-producing helper T cells that are responsible for autoimmune inflammatory diseases may counteract Treg cells even in allergic diseases. The Th2 cells that are capable of producing of high levels of tumor necrosis factor-α may also be involved in inflammation in allergic diseases. In this review, we further discuss the role of Th1, Th2, interleukin 17-producing helper T cells, and Treg cells in allergic diseases by using the balancing square model and the factors differentiating between patients with clinical manifestations of allergic symptomatic and atopic individuals who are sensitized but asymptomatic. Keywords: helper T cells, regulatory T cells, interleukin 17, mast cells, thymic stromal lymphopoietin

Hepatic stellate cells (HSCs) are strategically located to interact with hepatocytes, sinusoidal endothelial and Kupffer cells, and hepatic resident and migratory cells of the immune system. Compelling evidence in recent years has demonstrated that HSCs recruit inflammatory and immune cells by producing specific cytokines and chemokines. Upon activation or appropriate stimulation, HSCs express or upregulate MHC class I and II and co-regulatory B7 family molecules (e.g., CD80, CD86, and B7-H1), but suppress activation/proliferation of conventional CD4+ and CD8+ T cells and cause their apoptosis. Paradoxically, HSCs induce expansion of regulatory CD4+CD25+FoxP3+ T cells (Tregs). Whereas HSC-expanded Tregs acquire greater immunosuppressive potential, HSC-modulated dendritic cells become poor stimulators of T-cell activation. These characteristics of HSCs are likely critical in the liver’s inherent tolerogenicity and potentially important in liver allograft tolerance. On the other hand, HSCs can present bacterial lipid antigens to natural killer T cells and play an important role in limiting bacterial infection.

γδ T cells and the gut share a special relationship. Following the unanticipated identification of the T cell receptor (TCR) γ chain cDNA and the subsequent identification of γδ T cells, there was intense interest in how these cells might be distinct from αβ T cells. It soon emerged that whereas γδ T cells usually accounted for less than 5% of T cells in mouse lymph nodes and spleen, they were conspicuously enriched within epithelia, as was first revealed for the mouse skin and soon thereafter for the gut, tongue, and uterus. Thus, mucosal epithelia, and particularly the gut, suggested a route to better understanding γδ T cell biology. Likewise, the finding of lymphocyte compartment asymmetry compounded the growing view that mucosa-associated lymphoid tissue (MALT) would have unique phenotypic and functional properties that would be key to its understanding, and that would be informed by the study of γδ T cells. Indeed, body surface immune responses, including those in the gut, are dysregulated in mice specifically lacking γδ T cells. This chapter will consider how a contemporary view of γδ T cell biology highlights the dual afferent and effector functions of mucosal T cells, regulating downstream responses and balancing the cost-benefits of attenuated versus immunogenic responses to body surface perturbation. Several key facts, some established many years ago, provide an essential preface to the chapter, while critical issues requiring further experimental resolution are also highlighted throughout.

Antibody-dependent cellular cytotoxicity (ADCC), a key effector function for the clinical effectiveness of monoclonal antibodies, is triggered by the engagement of the antibody Fc domain with the Fcγ receptors expressed by innate immune cells such as natural killer (NK) cells and macrophages. Here, we fused cancer cell-binding peptides to the Fc domain of human IgG1 to engineer novel peptide-Fc fusion proteins with ADCC activity. The designed fusion proteins were expressed in human embryonic kidney 293T cells, followed by purification and characterization by western blots. One of the engineered variants (WN-Fc), bound with high affinity to a wide range of solid tumor cell lines (e.g., colon, lung, prostate, skin, ovarian, and mammary tumors). Treatment of cancer cells with the engineered peptide-Fc fusions in the presence of effector NK cells potentially enhanced cytotoxicity, degranulation, and interferon-γ production by NK cells when compared to cells treated with the Fc control. The presence of competing peptides inhibited NK cell activation. Furthermore, a bispecific peptide-Fc fusion protein activated NK cells against HER-1- and/or HER-2-expressing cancer cells. Collectively, the engineered peptide-Fc fusions constitute a new promising strategy to recruit and activate NK cells against tumor cells, a primary goal of cancer immunotherapy.

CD4+ T cells emerge from thymic selection programmed for fixed antigenic specificity. However, with the exception of natural regulatory T cells (nTreg cells), they are multipotent for alternative developmental programs that diverge contingent upon the peripheral microenvironment in which antigen is first recognized. Antigen recognition in the presence of proinflammatory cytokines elicited from antigen-presenting cells (APCs) or other innate immune cells by microbe-associated molecular patterns (MAMPs) drives the differentiation of antigen-naive CD4+ T cells into distinct effector T cell subsets that are characterized by expression of signature cytokines that orchestrate different patterns of immunity. The intestines harbor the largest collection of CD4+ T cells in the body, including the largest number of effector T cells at homeostasis. Intestinal effector T cell responses are generally directed against antigens derived from microbes that penetrate innate barrier defenses in the gut, whether derived from the largest and most diverse commensal microbiota, or pathogenic bacteria, viruses, helminthic parasites, or fungi. In certain disease states, effector T cells can also be reactive to dietary or self-antigens. Whereas the physiologic role of effector T cell responses is pathogen eradication, when inadequately restrained or dysregulated, effector T cell responses can cause injury to host tissues and lead to chronic, immune-mediated disease.

Intraepithelial lymphocytes or IEL consist exclusively of T lymphocytes that reside interspersed between epithelial cells in the epithelium of the small and large intestine, the biliary tract, the oral cavity, the lung, the upper respiratory tract and the reproductive tract as well as in the skin. Together, these intraepithelial T cells or Epi-T cells form the biggest population of lymphocytes in the whole body, and they are most numerous within the single layer of epithelial cells that lines the lumen of the intestine. This epithelial barrier forms the main interface between the inner core of the body and the environment and, consequently, it also forms the foremost entry port for pathogens. All Epi-T cells are antigen-experienced T cells, which typically display a cytotoxic functional phenotype. This chapter will focus on the characteristics, development, functional differentiation, and protective and pathogenic roles of various TCRαβ Epi-T cells, mainly of the intestine. The intraepithelial TCRγδ T cells will be discussed in Chapter 37 .

In the present paper, an in vitro model was established in which the interaction between influenza virus-specific CD8+ T cells and human airway epithelial cells can be studied. To this end, the human lung epithelial cell line A549 was transduced with the HLA-A*0201 gene. This MHC class I allele is involved in the presentation of the immunodominant M1 58–66 cytotoxic T lymphocyte (CTL) epitope of the influenza A virus matrix protein. The A549-HLA-A2 cells and a CD8+ T cell clone specific for the M1 58–66 epitope were used to evaluate ISCOMATRIX ® (IMX), which is considered a potential mucosal adjuvant for influenza vaccines, for its capacity to activate virus-specific CTL after incubation with epithelial cells. It was found that virus infected epithelial cells activated virus-specific CTL efficiently. However, incubation of epithelial cells with ISCOMATRIX ® and recombinant M1 protein activated CD8+ T cells inefficiently, unlike the incubation of C1R cells expressing a HLA-A2 trans gene or HLA-A2+ B-lymphoblastoid cells with these reagents. It was concluded that this lack of antigen presentation by epithelial cells indicate that these cells are not subject to killing by virus-specific CTL upon instillation with ISCOMATRIX ® -based vaccines, which may be a favorable property of mucosal vaccines.

Background Respiratory viral infections are known to be a risk factor for the exacerbation of asthma. In a model of asthma with influenza A virus infection, dendritic cells play an important role during antigen sensitization and antigen challenge. However, the role of T cells in the asthma-influenza A model was unclear. The aim of the present study was to assess the roles of T cells during antigen sensitization and antigen challenge in the asthmatic model. Methods C57BL/6 mice were infected with influenza A virus and were sensitized with inhaled antigen during the acute phase of the virus infection. Anti-CD4 or anti-CD8 monoclonal antibodies were administered during antigen sensitization or antigen challenge to evaluate the role of CD4 + or CD8 + T cells in this murine model of asthma. The onset of asthma was determined by eosinophil recruitment into the lung. Results During antigen sensitization, depletion of either CD4 + or CD8 + T cells resulted in an absence of eosinophil infiltration into the lung after antigen challenge. However, during antigen challenge, depletion of CD4 + T cells did cause such an absence of eosinophil infiltration. Conclusions During antigen sensitization, both CD4 + and CD8 + T cells were required in C57BL/6 mice for exacerbation of asthma. During antigen challenge, CD4 + T cells were important for the onset of asthma, whereas CD8 + T cells do not affect eosinophil recruitment into the lung.

Upon encounter with antigen and depending on the cytokine milieu, T helper (Th) cells can differentiate into various effector T cell subsets, including the well-defined Th1 and Th2 subsets as well as the more recently discovered Th17, Th9, and follicular T helper (TFH) subsets. Among these, self-reactive Th1 and Th17 cells have been associated with organ-specific autoimmunity, while self-reactive TFH cells have been shown to promote aberrant B cell responses in systemic autoimmune diseases. On the other hand, regulatory T cell subsets including Foxp3+ regulatory T cells (Tregs) and type 1 regulatory T cells (Tr1) can regulate autoimmunity by suppressing effector T cell responses. Here, we give an overview of the different Th cell subsets, their development, and how the interplay between them can promote or inhibit autoimmune tissue inflammation.

Natural killer (NK) cells are granular lymphocytes that play important roles in immunity against viruses and in the immune surveillance of tumors. In addition to being a potent innate source of IFN-γ, NK cells hold cytoplasmic granula that contain perforin and granzymes involved in cell-mediated cytotoxicity. NK cells express various types of immunoreceptors that are all designed to sense pathological changes of self cells. NK cells differ from lymphocytes of the adaptive immune system, such as T and B cells, because they do not express one major immune recognition receptor generated by recombination of receptor elements. Instead, NK cells express an arsenal of polymorphic inhibitory and activating, germline-encoded immunoreceptors with variegated expression that interact with ligands expressed by self cells. The balance of inhibitory and activating input to an NK cell determines its activation state, and harnessing the power of NK cells by exploiting this polymorphic inhibitory receptor/ligand system has become a constituent of clinical therapies.

CD4 + T cells are derived from the thymus and activated in the periphery when their T-cell receptors encounter cognate ligands. In response to specific cytokine milieu during T-cell activation, naive CD4 + T cells differentiate into distinct T helper (Th) subsets that secrete unique sets of cytokines. Through cytokine production, activated Th cells orchestrate adaptive immune responses to infectious pathogens, noninfectious environmental agents, and self-antigens. Specific cytokines and transcription factors play critical roles in the development, activation, fate determination, plasticity, and memory generation of heterogeneous Th cell subsets. Abnormality during these processes often leads to immune-related human diseases.