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Aim: Porphyromonas gingivalis can synthesize an extracellular capsule and different serotypes have been described based on capsular antigenicity. On dendritic cells (DCs), the type of capsule present plays a role on the strength of the developed immune response. This study aimed to investigate the T-lymphocyte responses when stimulated with autologous mature DCs exposed to different P. gingivalis K-serotypes., Materials and Methods: Naïve CD4(+) T-lymphocytes were obtained from healthy subjects and stimulated with autologous DCs primed with increasing multiplicity of infections of the different P. gingivalis K-serotypes. The Th1, Th2, Th17 and T-regulatory cytokines and transcription factor levels were quantified., Results: Distinct types of response were detected when T-lymphocytes were stimulated by DCs primed with the different P. gingivalis K-serotypes. T-lymphocytes stimulated by K1 or K2-primed DCs elicited higher levels of Th1 and Th17-associated cytokines, T-bet and RORC2 than T-lymphocytes stimulated with DCs primed with the other serotypes. Conversely, the serotypes K3-K5 induced higher levels of Th2-associated cytokines and GATA-3 than the others., Conclusions: These results demonstrate that DCs primed with the different P. gingivalis K-serotypes elicited distinct T-cell responses. Strains K1 (W83) and K2 (HG184) induced a Th1/Th17 pattern of immune response and K3 (A7A1-28), K4 (ATCC(®49417™) ), and K5 (HG1690) a Th2 response., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The activation of T cells is a tightly regulated process that has evolved to maximize protective immune responses to pathogens while minimizing damage to self-tissues. A delicate balance of cell-intrinsic, costimulatory, and transcriptional pathways as well as micro-environmental cues such as local cytokines controls the magnitude and nature of T-cell responses in vivo. The discovery of functional small noncoding RNAs called micro-RNAs (miRNAs) has introduced new mechanisms that contribute to the regulation of protein translation and cellular responses to stimuli. miRNAs are short (approximately 22 bp) RNA species, which bind to mRNAs and suppress translation. Due to their short length and imperfect base pairing requirements, each miRNA has the potential to regulate various pathways through the translational inhibition of multiple mRNAs. The human and mouse genomes each encode hundreds of miRNAs, and studying the function of miRNAs has led to the realization that they play important roles in diverse biological processes from development and cancer to immunity. This review focuses on the function of mir-155 in T cells and the impact of this miRNA on autoimmunity, tumor immunity, and pathogen-induced immunity.

Postinfluenza pneumococcal pneumonia is a common cause of death in humans. However, the role of IL-27 in the pathogenesis of secondary pneumococcal pneumonia after influenza is unknown. We now report that influenza infection induced pulmonary IL-27 production in a type I IFN-α/β receptor (IFNAR) signalling-dependent manner, which sensitized mice to secondary pneumococcal infection downstream of IFNAR pathway. Mice deficient in IL-27 receptor were resistant to secondary pneumococcal infection and generated more IL-17A-producing γδ T cells but not αβ T cells, thereby leading to enhanced neutrophil response during the early phase of host defence. IL-27 treatment could suppress the development of IL-17A-producing γδ T cells activated by Streptococcus pneumoniae and dendritic cells. This suppressive activity of IL-27 on γδ T cells was dependent on transcription factor STAT1. Finally, neutralization of IL-27 or administration of IL-17A restored the role of γδ T cells in combating secondary pneumococcal infection. Our study defines what we believe to be a novel role of IL-27 in impairing host innate immunity against pneumococcal infection.

Response of an immune system to a pathogen attack depends on the balance between the host immune defense and the virulence of the pathogen. Investigation of molecular interactions between the proteins of a host and a pathogen helps in identifying the pathogenic proteins. It is necessary to understand the dynamics of a normally behaved host system to evaluate the capacity of its immune system upon pathogen attack. In this study, we have compared the behavior of an unperturbed and pathogen perturbed host system. Moreover, we have developed a formalism under Flux Balance Analysis (FBA) for the optimization of conflicting objective functions. We have constructed an integrated pathway system, which includes Staphylococcal Superantigen (SAg) expression regulatory pathway and TCR signaling pathway of Homo sapiens. We have implemented the method on this pathway system and observed the behavior of host signaling molecules upon pathogen attack. The entire study has been divided into six different cases, based on the perturbed/unperturbed conditions. In other words, we have investigated unperturbed and pathogen perturbed human TCR signaling pathway, with different combinations of optimization of concentrations of regulatory and signaling molecules. One of these cases has aimed at finding out whether minimization of the toxin production in a pathogen leads to the change in the concentration levels of the proteins coded by TCR signaling pathway genes in the infected host. Based on the computed results, we have hypothesized that the balance between TCR signaling inhibitory and stimulatory molecules can keep TCR signaling system into resting/stimulating state, depending upon the perturbation. The proposed integrated host-pathogen interaction pathway model has accurately reflected the experimental evidences, which we have used for validation purpose. The significance of this kind of investigation lies in revealing the susceptible interaction points that can take back the Staphylococcal Enterotoxin (SE)-challenged system within the range of normal behavior.

Peripheral lymphoid organs from 2 different groups of laboratory rat's was studied (30 animals in each group). 1) Gnotobionts received from experimental - biological models Iffa-Credo laboratory (Lyon, France), 2) Ordinary conventional animals from the same laboratory, contained in standard conditions of vivarium microbial environment (control group). Animals from each group were subdivided into 2 aged categories (15 in each group): mature (8-12 month, 200,0 - 250,0 g) and aged (I period of old age 24-32 month; 300,0-450 g.) animals. Histological, electron-microscopic and morphmetric methods of studies were used. Correlations between morphological peculiarities and cellular composition of the rat's lymphoid tissue with antigenic load and age were determined. Namely, gnotobiont rat's lymphoid tissue contains less mature population, hence inactive lymphoid cells compared with conventional animals. However, with age this processes in both animal groups acquire a similar orientation.

We report a case of mediastinal fibrosis secondary to histoplasmosis in a 9-year old male, who presented with superior vena cava syndrome. He was successfully treated by percutaneous superior vena cava stent placement in the outpatient cardiac catheterization laboratory., (Copyright © 2013 Wiley Periodicals, Inc.)

Autophagy is a fundamental eukaryotic pathway that has multiple effects on immunity. Autophagy is induced by pattern recognition receptors and, through autophagic adaptors, it provides a mechanism for the elimination of intracellular microorganisms. Autophagy controls inflammation through regulatory interactions with innate immune signalling pathways, by removing endogenous inflammasome agonists and through effects on the secretion of immune mediators. Moreover, autophagy contributes to antigen presentation and to T cell homeostasis, and it affects T cell repertoires and polarization. Thus, as we discuss in this Review, autophagy has multitiered immunological functions that influence infection, inflammation and immunity.

The important role played by cytokines in host innate immunity and the interaction of subsets of immune and inflammatory cells through cytokines offer avenues for immune interventions. We investigated 16 cytokine gene responses in the Japanese pufferfish, Takifugu rubripes orally treated with a heat-killed lactic acid bacterium (LAB), Lactobacillus paracasei spp. paracasei (strain 06TCa22) (Lpp) isolated from a Mongolian dairy product at 1mgg(-1)body weightd(-1) for 3days. Additionally, we assessed superoxide anion production (SAP) and phagocytic activity (PA) of head kidney cells and resistance to Vibrio harveyi infection in treated fish. Significant up-regulation of pro-inflammatory (IL-1β, IL-6, IL-17A/F-3, TNF-α and TNF-N), cell-mediated immunity inducing (IL-12p35, IL-12p40 and IL-18), antiviral/intra-cellular pathogen killing (I-IFN-1 and IFN-γ), anti-inflammatory (IL-10) and peripheral T cell expansion and survival controlling (IL-2, IL-7, IL-15, IL-21 and TGF-β1) cytokines was observed in the treated fish. Furthermore, significantly increased SAP, PA and pathogen resistance were observed in the treated fish compared to untreated fish. Our results indicate the enhancement of cytokine mediated immunity in T. rubripes by the use of the heat-killed Lpp as a potential immunostimulant and would be of great use in immunomodulation trials with the possibility to monitor positive immune response., (© 2013.)

Chronic granulomatous disease (CGD) patients are highly susceptible to invasive aspergillosis and might benefit from aspergillus-specific T cell immunotherapy, which has shown promise in treating those with known T cell defects such as haematopoietic stem cell transplant (HSCT) recipients. But whether such T cell defects contribute to increased risks for aspergillus infection in CGD is unclear. Hence, we set out to characterize the aspergillus-specific T cell response in CGD. In murine CGD models and in patients with CGD we showed that the CD4(+) T cell responses to aspergillus were unimpaired: aspergillus-specific T cell frequencies were even elevated in CGD mice (P < 0·01) and humans (P = 0·02), compared to their healthy counterparts. CD4-depleted murine models suggested that the role of T cells might be redundant because resistance to aspergillus infection was conserved in CD4(+) T cell-depleted mice, similar to wild-type animals. In contrast, mice depleted of neutrophils alone or neutrophils and CD4(+) T cells developed clinical and pathological evidence of pulmonary aspergillosis and increased mortality (P < 0·05 compared to non-depleted animals). Our findings that T cells in CGD have a robust aspergillus CD4(+) T cell response suggest that CD4(+) T cell-based immunotherapy for this disease is unlikely to be beneficial., (© 2013 British Society for Immunology.)

Background: Apoptosis is a highly controlled process of cell death that can be induced by periodontopathogens. The present study aimed to investigate the expression of Fas and Bcl-2 proteins by CD3+ T cells in vitro under stimulation by total Porphyromonas gingivalis antigens and purified recombinant P. gingivalis HmuY protein., Results: CD3+ T cells derived from CP patients and stimulated with HmuY expressed higher levels of Bcl-2 compared to identical cells stimulated with P. gingivalis crude extract or cells derived from NP control subjects (p = 0.043)., Conclusion: The authors hypothesize that P. gingivalis HmuY plays a role in the pathogenesis of chronic periodontitis, possibly by reducing or delaying apoptosis in T cells through a pathway involving the Bcl-2 protein.

Objective: To determine whether there were any defects in the presentation of the Mycobacterium tuberculosis antigen by monocytes from patients with tuberculosis (TB) and the role of vitamin D in the defence against M. tuberculosis., Design: A prospective study aimed at analysing the presentation of the M. tuberculosis antigen by monocytes and the response to vitamin D treatment in three groups of participants: 1) those with active TB, 2) those with healed TB and 3) those with frequent TB contact., Results: The antigen presentation ability of monocytes of persons in the frequent contact group was significantly higher than that of the active TB and healed TB groups. There was no difference between patients with active and healed TB. In addition, 1,25(OH)2D3 increased the presentation of mycobacterial antigens by monocytes from participants with frequent TB contact, but not those with active or healed TB., Conclusion: Patients with active and healed TB exhibit defective M. tuberculosis presentation in monocytes. The administration of vitamin D did not correct this defect in monocytes from participants with active or healed TB, but could increase antigen presentation by monocytes in participants with frequent TB contact.

Background: The HLA (human leukocyte antigen) molecules that present pathogen-derived epitopes to T cells are highly diverse. Correspondingly, many pathogens such as HIV evolve epitope variants in order to evade immune recognition. In contrast, another persistent human pathogen, Mycobacterium tuberculosis, has highly conserved epitope sequences. This raises the question whether there is also a difference in the ability of these pathogens' epitopes to bind diverse HLA alleles, referred to as an epitope's binding promiscuity. To address this question, we compared the in silico HLA binding promiscuity of T cell epitopes from pathogens with distinct infection strategies and outcomes of human exposure., Methods: We used computer algorithms to predict the binding affinity of experimentally-verified microbial epitope peptides to diverse HLA-DR, HLA-A and HLA-B alleles. We then analyzed binding promiscuity of epitopes derived from HIV and M. tuberculosis. We also analyzed promiscuity of epitopes from Streptococcus pyogenes, which is known to exhibit epitope diversity, and epitopes of Bacillus anthracis and Clostridium tetani toxins, as these bacteria do not depend on human hosts for their survival or replication, and their toxin antigens are highly immunogenic human vaccines., Results: We found that B. anthracis and C. tetani epitopes were the most promiscuous of the group that we analyzed. However, there was no consistent difference or trend in promiscuity in epitopes contained in HIV, M. tuberculosis, and S. pyogenes., Conclusions: Our results show that human pathogens with distinct immune evasion strategies and epitope diversities exhibit equivalent levels of T cell epitope promiscuity. These results indicate that differences in epitope promiscuity do not account for the observed differences in epitope variation and conservation.

Dominant Vγ2Vδ2 T-cell subset exist only in primates, and recognize phosphoantigen from selected pathogens including M. tuberculosis(Mtb). In vivo function of Vγ2Vδ2 T cells in tuberculosis remains unknown. We conducted mechanistic studies to determine whether earlier expansion/differentiation of Vγ2Vδ2 T cells during Mtb infection could increase immune resistance to tuberculosis in macaques. Phosphoantigen/IL-2 administration specifically induced major expansion and pulmonary trafficking/accumulation of phosphoantigen-specific Vγ2Vδ2 T cells, significantly reduced Mtb burdens and attenuated tuberculosis lesions in lung tissues compared to saline/BSA or IL-2 controls. Expanded Vγ2Vδ2 T cells differentiated into multifunctional effector subpopulations capable of producing anti-TB cytokines IFNγ, perforin and granulysin, and co-producing perforin/granulysin in lung tissue. Mechanistically, perforin/granulysin-producing Vγ2Vδ2 T cells limited intracellular Mtb growth, and macaque granulysin had Mtb-bactericidal effect, and inhibited intracellular Mtb in presence of perforin. Furthermore, phosphoantigen/IL2-expanded Vγ2Vδ2 T effector cells produced IL-12, and their expansion/differentiation led to enhanced pulmonary responses of peptide-specific CD4+/CD8+ Th1-like cells. These results provide first in vivo evidence implicating that early expansion/differentiation of Vγ2Vδ2 T effector cells during Mtb infection increases resistance to tuberculosis. Thus, data support a rationale for conducting further studies of the γδ T-cell-targeted treatment of established TB, which might ultimately help explore single or adjunctive phosphoantigen expansion of Vγ2Vδ2 T-cell subset as intervention of MDR-tuberculosis or HIV-related tuberculosis.

Recent evidence indicates that monocytes and macrophages express T cell receptor (TCR)αβ-like combinatorial immune receptors. Here, we demonstrate the presence of a second recombinatorial immunoreceptor, which is structurally based on the TCR γ- and δ-chains, in human and murine monocytes and differentially activated macrophages (referred to here as TCRL(m)γδ). In vitro, infection of macrophages with mycobacteria and gram positive or gram negative bacteria induced expression of donor-specific and differential TCRL(m)Vδ repertoires indicating that the novel immunoreceptor represents a dynamic flexible host defense system that responds to bacterial challenge. In vivo, we find that TCRL(m)γδ bearing macrophages, which express highly restricted repertoires of the antigen-binding Vδ chain, accumulate in the cerebrospinal fluid in acute bacterial meningitis and in advanced lesions of atherosclerosis. These results identify an as yet unrecognized monocyte/macrophage subpopulation that bears combinatorial TCRL(m)γδ immune receptors, and is associated with both acute and chronic inflammatory diseases. Moreover, they indicate that the monocytic lineage uses the same bipartite system of TCRαβ/TCRγδ-based combinatorial immune receptors that is present in T cells. Our findings suggest specific roles of monocytes/macrophages in various inflammatory conditions and lend further evidence that flexible immune recognition in higher vertebrates operates on a broader cellular basis than previously thought., (Copyright © 2013. Published by Elsevier GmbH.)

Porphyromonas gingivalis is a major pathogen in periodontal disease and is associated with immune dysbiosis. In this study, we found that P. gingivalis did not induce the expression of the T-cell chemokine IP-10 (CXCL10) from neutrophils, peripheral blood mononuclear cells (PBMCs), or gingival epithelial cells. Furthermore, P. gingivalis suppressed gamma interferon (IFN-γ)-stimulated release of IP-10, ITAC (CXCL11), and Mig (CXCL9) from epithelial cells and inhibited IP-10 secretion in a mixed infection with the otherwise stimulatory Fusobacterium nucleatum. Inhibition of chemokine expression occurred at the level of gene transcription and was associated with downregulation of interferon regulatory factor 1 (IRF-1) and decreased levels of Stat1. Ectopic expression of IRF-1 in epithelial cells relieved P. gingivalis-induced inhibition of IP-10 release. Direct contact between P. gingivalis and epithelial cells was not required for IP-10 inhibition. These results highlight the immune-disruptive potential of P. gingivalis. Suppression of IP-10 and other Th1-biasing chemokines by P. gingivalis may perturb the balance of protective and destructive immunity in the periodontal tissues and facilitate the pathogenicity of oral microbial communities.

Background: Myeloid-derived suppressor cells (MDSCs) are present in large numbers in blood of mice and humans with cancer, and they strongly inhibit T-cell and natural killer (NK) cell responses, at young and old age. We found that a highly attenuated bacterium Listeria monocytogenes (Listeria(at))-infected MDSC and altered the immune-suppressing function of MDSC., Methods: Young (3 months) and old (18 months) BALB/cByJ mice with metastatic breast cancer (4T1 model) were immunised with Listeria(at) semi-therapeutically (once before and twice after tumour development), and analysed for growth of metastases and primary tumour, in relation to MDSC-, CD8 T-cell and NK cell responses., Results: We found that Listeria(at)-infected MDSC, which delivered Listeria(at) predominantly to the microenvironment of metastases and primary tumours, where they spread from MDSC into tumour cells (infected tumour cells will ultimately become a target for Listeria-activated immune cells). Immunotherapy with Listeria(at) significantly reduced the population of MDSC in blood and primary tumours, and converted a remaining subpopulation of MDSC into an immune-stimulating phenotype producing IL-12, in correlation with significantly improved T-cell and NK cell responses to Listeria(at) at both ages. This was accompanied with a dramatic reduction in the number of metastases and tumour growth at young and old age., Conclusions: Although preclinical studies show that immunotherapy is less effective at old than at young age, our study demonstrates that Listeria(at)-based immunotherapy can be equally effective against metastatic breast cancer at both young and old age by targeting MDSC.

Coronin 1, which is a member of the evolutionary conserved coronin protein family that is highly expressed in all leukocytes is involved in the activation of the Ca(2+)/calcineurin signaling pathway following cell surface stimulation in T cells, B cells as well as macrophages. Mice deficient for coronin 1 have strongly reduced peripheral T cell numbers as a result of a lack of pro-survival signals for naïve T cells. Whether or not impaired antigen processing and presentation in the absence of coronin 1 expression contributes to this reduction of T cell numbers is unknown. We here show that coronin 1-deficient bone marrow-derived dendritic cells develop normally, and that wild type and coronin 1-deficient dendritic cells were equally able to induce antigen-specific proliferation of T cells. Furthermore, upon immunization, in vivo proliferation of adoptively transferred antigen-specific T cells was comparable in wild type and coronin 1-deficient mice. Finally, infection of wild type and coronin 1-deficient dendritic cells with an ovalbumin-expressing Listeria monocytogenes strain induced comparable levels of ovalbumin-specific T cells responses. Together these results suggest that coronin 1 is dispensable for antigen processing and presentation by dendritic cells., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Cells of the innate immune system regulate both adaptive immune responses and the maintenance of tolerance, especially in the gut. However, relatively little is known about the effects of complement on lymphocyte homeostasis., Objective: This study explored complement C3 deficiency in mice and human subjects for its effect on intestinal tolerance., Methods: C3-deficient mice and control C57BL/6 mice were fed ovalbumin (OVA) by means of gavage, and subsequent response to immunization with OVA in Freund's adjuvant was monitored. Serum antibodies against commensal microbes were measured, and the activation status of peripheral blood lymphocytes bearing mucosal homing markers was determined from 2 rare cases of C3-deficient patients., Results: We show in C3-deficient mice and human patients that intestinal tolerance fails in the absence of functional complement. In contrast to wild-type control animals, in which oral tolerance was induced, intragastric administration of OVA did not result in a significantly decreased response to subsequent subcutaneous OVA challenge in C3-deficient mice. In the jejunum of C3-deficient mice the cytokine ratio between IL-10 and IFN-γ or IL-17 levels was decreased, indicating a shift in favor of proinflammatory cytokines. In 2 C3-deficient children the frequency of gut-homing T cells expressing activation markers was increased, and the patients had increased serum IgG levels against gut commensal microbes. The data also suggest that the impaired oral tolerance was at least partly caused by the absence of signaling through C3-binding complement regulators in T cells., Conclusions: Taken together, our results identify complement as an important and nonredundant regulator of intestinal tolerance., (Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

The need for rapid diagnostic tests that can be applied in non-expert settings may now be greater than ever before, due to changes in leprosy control programmes and the decrease in special expertise required for (early) diagnosis of leprosy. However, there is no test available that can detect asymptomatic Mycobacterium leprae infection or predict progression of infection to clinical disease. The characteristics of the leprosy disease spectrum, in which both cellular and humoral immunity against M. leprae determine the outcome of infection, are pre-eminently suitable for development of tests that simultaneously detect biomarkers specific for both types of immune responses, thereby covering the complete immunological leprosy spectrum. Since publication of the M. leprae genome, many research groups have investigated the potential of M. leprae-unique antigens in serologic as well as T cell assays. Despite the early promise of the genome towards identifying antigens that induce M. leprae-specific T cells, it took more than a decade before promising candidates were identified. This review describes recent studies on M. leprae-specific T cell responses and discusses the application of measuring specific cellular mediated immune responses possibly combined with serologic responses in field-friendly tests for early diagnosis of M. leprae exposure and infection.

Developing T cells express diverse antigen receptors whose specificities are not prematched to the foreign antigens they eventually encounter. Past experiments have revealed that thymocytes must productively signal in response to self antigens to mature and enter the peripheral T cell pool (positive selection), but how this process enhances effective mature T cell responses to foreign antigen is not fully understood. Here we have documented an unsuspected connection between thymic recognition events and foreign antigen-driven T cell responses. We find that the strength of self-reactivity is a clone-specific property unexpectedly directly related to the strength of T cell receptor (TCR) binding to presented foreign antigen. T cells with receptors showing stronger interaction with self dominate in responses to infections and accumulate in aging individuals, revealing that positive selection contributes to effective immunity by skewing the mature TCR repertoire toward highly effective recognition of pathogens that pose a danger to the host., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Chlamydia pneumoniae is a respiratory pathogen involved in the onset of chronic inflammatory pathologies. Dendritic cells (DC), are major players in spreading of C. pneumoniae from the lungs, a crucial step leading to disseminated infections. Less is known concerning modulation of DC functions consequent to encounter with the bacterium. In order to address this aspect, human monocyte-derived (MD)DC were infected with C. pneumoniae. After internalization bacterial counts increased in MDDC, as well as the expression of CPn1046, a gene involved in bacterial metabolism, with a peak 48 h after the infection. Infected MDDC switched to the mature stage, produced IL-12p70, IL-1β, IL-6, and IL-10, and drove a mixed Type 1/Type 17 polarization. Intracellular pathways triggered by C. pneumoniae involved Toll-like receptor (TLR) 2. Indeed, TLR2 was activated by C. pneumoniae in transfected HEK 293 cells, and C. pneumoniae-mediated phosphorylation of ERK1/2 was inhibited by an anti-TLR2 antibody in MDDC. When an ERK1/2 inhibitor was used, IL-12p70 and IL-10 release by MDDC was reduced and T cell polarization shifted towards a Type 2 profile. Overall, our findings unveiled the role played by TLR2 and ERK1/2 induced by C. pneumoniae to affect DC functions in a way that contributes to a Type 1/Type 17 pro-inflammatory response., (Copyright © 2012 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Suppressor of cytokine signalling 3 (SOCS3) negatively regulates STAT3 activation in response to several cytokines such as those in the gp130-containing IL-6 receptor family. Thus, SOCS3 may play a major role in immune responses to pathogens. In the present study, the role of SOCS3 in M. tuberculosis infection was examined. All Socs3(fl/fl) LysM cre, Socs3(fl/fl) lck cre (with SOCS3-deficient myeloid and lymphoid cells, respectively) and gp130(F/F) mice, with a mutation in gp130 that impedes binding to SOCS3, showed increased susceptibility to infection with M. tuberculosis. SOCS3 binding to gp130 in myeloid cells conveyed resistance to M. tuberculosis infection via the regulation of IL-6/STAT3 signalling. SOCS3 was redundant for mycobacterial control by macrophages in vitro. Instead, SOCS3 expression in infected macrophages and DCs prevented the IL-6-mediated inhibition of TNF and IL-12 secretion and contributed to a timely CD4+ cell-dependent IFN-γ expression in vivo. In T cells, SOCS3 expression was essential for a gp130-independent control of infection with M. tuberculosis, but was neither required for the control of infection with attenuated M. bovis BCG nor for M. tuberculosis in BCG-vaccinated mice. Socs3(fl/fl) lck cre mice showed an increased frequency of γδ+ T cells in different organs and an enhanced secretion of IL-17 by γδ+ T cells in response to infection. Socs3(fl/fl) lck cre γδ+ T cells impaired the control of infection with M. tuberculosis. Thus, SOCS3 expression in either lymphoid or myeloid cells is essential for resistance against M. tuberculosis via discrete mechanisms.

Pro-inflammatory cytokines participate in the induction of ischemic stroke. So far, their participation in the cerebral ischemia was proven for the tumor necrosis factor TNF-α, interleukin-1 (IL-1), and interleukin-6 (IL-6). The release of the pro-inflammatory cytokines into the extracellular space causes the enlargement of the brain damage region, and consequently increases the neurological deficit and negatively affects the survival rate prognoses. That is confirmed by the increased concentration of pro-inflammatory cytokines in blood and the cerebrospinal fluid of patients with brain stroke, as well as by the research on the induced/experimental cerebral ischemia in animals. The pro-inflammatory cytokines participate in the migration of the reactive T lymphocytes to the regions of brain ischemia where they enhance the nerve tissue damage by down-regulation of microcirculation, induce the pro-thrombotic processes and release other neurotoxic cytokines. Also, in the early stage of cerebral ischemia, cytokines activate the axis hypothalamus-pituitary gland-adrenal cortex and increase the cortisol concentration in blood, what results in the decreased resistance to infectious diseases. Administration of the inhibitor of the interleukin-1 receptor (IL-1Ra) inhibits the inflammatory processes in the region of brain ischemia, and subsequently improves the prognosis for the size of the neurological deficit and the survival rate, as well as resistance to infectious diseases.

Mycoplasmas cause chronic respiratory diseases in animals and humans, and to date, development of vaccines have been problematic. Using a murine model of mycoplasma pneumonia, lymphocyte responses, specifically T cells, were shown to confer protection as well as promote immunopathology in mycoplasma disease. Because T cells play such a critical role, it is important to define the role of antigen presenting cells (APC) as these cells may influence either exacerbation of mycoplasma disease pathogenesis or enhancement of protective immunity. The roles of APC, such as dendritic cells and/or macrophages, and their ability to modulate adaptive immunity in mycoplasma disease are currently unknown. Therefore, the purpose of this study was to identify individual pulmonary APC populations that may contribute to the activation of T cell responses during mycoplasma disease pathogenesis. The present study indeed demonstrates increasing numbers of CD11c(-) F4/80(+) cells, which contain macrophages, and more mature/activated CD11c(+) F4/80(-) cells, containing DC, in the lungs after infection. CD11c(-) F4/80(+) macrophage-enriched cells and CD11c(+) F4/80(-) dendritic cell-enriched populations showed different patterns of cytokine mRNA expression, supporting the idea that these cells have different impacts on immunity in response to infection. In fact, DC containing CD11c(+) F4/80(-) cell populations from the lungs of infected mice were most capable of stimulating mycoplasma-specific CD4(+) Th cell responses in vitro. In vivo, these CD11c(+)F4/80(-) cells were co-localized with CD4(+) Th cells in inflammatory infiltrates in the lungs of mycoplasma-infected mice. Thus, CD11c(+)F4/80(-) dendritic cells appear to be the major APC population responsible for pulmonary T cell stimulation in mycoplasma-infected mice, and these dendritic cells likely contribute to responses impacting disease pathogenesis.

Background: Enteroaggregative Escherichia coli (EAEC) is recognized as an emerging cause of persistent diarrhea and enteric disease worldwide. Mucosal immunity towards EAEC infections is incompletely understood due in part to the lack of appropriate animal models. This study presents a new mouse model and investigates the role of peroxisome proliferator-activated receptor gamma (PPARγ) in the modulation of host responses to EAEC in nourished and malnourished mice., Methods/principal Findings: Wild-type and T cell-specific PPARγ null C57BL/6 mice were fed protein-deficient diets at weaning and challenged with 5×10(9)cfu EAEC strain JM221 to measure colonic gene expression and immune responses to EAEC. Antigen-specific responses to E. coli antigens were measured in nourished and malnourished mice following infection and demonstrated the immunosuppressive effects of malnutrition at the cellular level. At the molecular level, both pharmacological blockade and deletion of PPARγ in T cells resulted in upregulation of TGF-β, IL-6, IL-17 and anti-microbial peptides, enhanced Th17 responses, fewer colonic lesions, faster clearance of EAEC, and improved recovery. The beneficial effects of PPARγ blockade on weight loss and EAEC clearance were abrogated by neutralizing IL-17 in vivo., Conclusions: Our studies provide in vivo evidence supporting the beneficial role of mucosal innate and effector T cell responses on EAEC burden and suggest pharmacological blockade of PPARγ as a novel therapeutic intervention for EAEC infection.

Autophagy is a cell biological pathway affecting immune responses. In vitro, autophagy acts as a cell-autonomous defense against Mycobacterium tuberculosis, but its role in vivo is unknown. Here we show that autophagy plays a dual role against tuberculosis: antibacterial and anti-inflammatory. M. tuberculosis infection of Atg5(fl/fl) LysM-Cre(+) mice relative to autophagy-proficient littermates resulted in increased bacillary burden and excessive pulmonary inflammation characterized by neutrophil infiltration and IL-17 response with increased IL-1α levels. Macrophages from uninfected Atg5(fl/fl) LysM-Cre(+) mice displayed a cell-autonomous IL-1α hypersecretion phenotype, whereas T cells showed propensity toward IL-17 polarization during nonspecific activation or upon restimulation with mycobacterial antigens. Thus, autophagy acts in vivo by suppressing both M. tuberculosis growth and damaging inflammation.

Background: Methicillin-resistant Staphylococcus aureus-associated glomerulonephritis (MRSA-GN), a syndrome in which superantigens play an important role in the pathogenesis of the infection, has been well described in adult patients but not previously recognized in children., Case Diagnosis/treatment: We report the case of a 6-year-old girl with MRSA-GN. She presented multiple malformations, including tracheal stenosis necessitating tracheotomy. She was admitted to our hospital because of acute pneumonia caused by a MRSA infection and was found to have proteinuria and abnormal renal function. MRSA was detected in her sputum, and this MRSA isolate produced toxic shock syndrome toxin-1, which acts as a superantigen and stimulates Vβ2(+) T cells. A blood test revealed that the number of circulating Vβ2(+) T cells expressing CD45RO, a marker of activation, was increased along with a concomitant elevation in the levels of serum immunoglobulins. Both are hallmarks of MRSA-GN. The eradication of MRSA using appropriate antibiotics resulted in the disappearance of the proteinuria; in contrast, corticosteroid treatment failed. To the best of our knowledge, this is the youngest patient to be diagnosed with MRSA-GN., Conclusions: In summary, there should be a high index of suspicion for MRSA-GN, even in the very young, in order to avoid the unnecessary use of immune suppressants in this context.

Toll-like receptors (TLRs) sense structural patterns in microbial molecules and initiate immune defense mechanisms. The structures of many extracellular and intracellular domains of TLRs have been studied in the last 10 years. These structures reveal the extraordinary diversity of TLR-ligand interactions. Some TLRs use internal hydrophobic pockets to bind bacterial ligands and others use solvent-exposed surfaces to bind hydrophilic ligands. The structures suggest a common activation mechanism for TLRs: ligand binding to extracellular domains induces dimerization of the intracellular domains and so activates intracellular signaling pathways. Recently, the structure of the death domain complex of one of the signaling adapters, myeloid differentiation factor 88 (MyD88), has been determined. This structure shows how aggregation of signaling adapters recruits downstream kinases. However, we are still far from a complete understanding of TLR activation. We need to study the structures of TLR7-10 in complex with their ligands. We also need to determine the structures of TLR-adapter aggregates to understand activation mechanisms and the specificity of the signaling pathways. Ultimately, we will have to study the structures of the complete TLR signaling complexes containing full-length receptors, ligands, signaling, and bridging adapters, and some of the downstream kinases to understand how TLRs sense microbial infections and activate immune responses against them., (© 2012 John Wiley & Sons A/S.)

The profile of selective modulation of hepatic cytochrome P450 (P450) gene expression caused by infection with the murine intestinal pathogen Citrobacter rodentium has been well characterized in multiple genetic backgrounds; yet, the mechanisms underlying this modulation are still not entirely understood. Although several studies have addressed the roles of cytokines from the innate immune system, the influence of the adaptive immune system is not known. To address this deficiency, we used mice harboring the severe combined immune deficiency (SCID) spontaneous mutation, which lack mature T and B lymphocytes and are unable to mount an acquired immune response. Female C57BL/6 (B6) and SCID mice were infected orally with C. rodentium and assessed for bacterial colonization/translocation and P450 and flavin monooxygenase-3 (Fmo3) expression levels after 7 days. SCID mice showed similar patterns of colonic bacterial colonization and a similar degree of colonic mucosal hypertrophy compared with infected B6 mice, but SCID mice displayed 6-fold greater bacterial translocation to the liver. In the SCID mice, Cyp4a10 and Cyp2b9 down-regulations were partially and fully blocked, respectively, whereas the regulation of other P450s and Fmo3 was similar in both strains. In the C3H genetic background, the SCID mutation also blocked the down-regulation of Cyp3a11, Cyp3a25, Cyp2d22, and Cyp2c29. The results clearly dissociate bacterial translocation to the liver from hepatic drug-metabolizing enzyme regulation and suggest a possible role of T cells, T-cell cytokines, or other proteins regulated by such cytokines in the selective regulation of a limited subset of hepatic P450 enzymes during C. rodentium infection.

This study aimed to describe the levels of circulating cytokine levels produced by Th lymphocytes (IFN-γ, IL-4, IL-10, IL-17A), as well as the levels of cytokines produced by monocytes/macrophages (TNF-α, IL-1β, IL-12), in patients with chronic infections caused by Staphylococcus aureus strains, particularly in the context of the diversification of their Agr system classes. The studies were conducted on adult patients, including 50 patients with chronic suppurative dermatitis, 40 patients with chronic infections of the upper respiratory tract and 25 healthy individuals (control group). Blood serum cytokine levels were measured by enzyme-linked immunosorbent assay (ELISA). S. aureus was detected in cultures of suppurative dermal exudates or of pharyngeal smears. Classes of Agr systems in the S. aureus strains were identified using polymerase chain reaction (PCR). In both groups of patients, on average, levels of IFN-γ were doubled, while levels of IL-17A were increased by 2.5-fold, which, however, was not accompanied by increased levels of TNF-α or IL-12. The data indicate that the development of S. aureus infection among the studied patients was linked to an impoverished cytokine response of monocytes/macrophages, while that induced by the pathogen lymphocytes Th17/Th1 may be responsible for promotion of the chronic inflammatory response. In parallel, no quantitative or qualitative differences were disclosed between cytokine responses manifested by subgroups of patients infected with S. aureus strains belonging to class IV Agr, as compared to patients infected with strains of classes I to III Agr. Nevertheless, in the patients, strains belonging to class IV Agr prevailed, which points to the preferential relationship between the class and the pathogenicity of S. aureus.

Background: Advanced stages of leprosy show T cell unresponsiveness and lipids of mycobacterial origin are speculated to modulate immune responses in these patients. Present study elucidates the role of phenolicglycolipid (PGL-1) and Mannose-capped lipoarabinomannan (Man-LAM) on TCR- and TCR/CD28- mediated signalling., Results: We observed that lipid antigens significantly inhibit proximal early signalling events like Zap-70 phosphorylation and calcium mobilization. Interestingly, these antigens preferentially curtailed TCR-triggered early downstream signalling events like p38 phosphorylation whereas potentiated that of Erk1/2. Further, at later stages inhibition of NFAT binding, IL-2 message, CD25 expression and T-cell blastogenesis by PGL-1 and Man-LAM was noted., Conclusion: Altogether, we report that Man-LAM and PGL-1 preferentially interfere with TCR/CD28-triggered upstream cell signalling events, leading to reduced IL-2 secretion and T-cell blastogenesis which potentially could lead to immunosupression and thus, disease exacerbation, as noted in disease spectrum.

B7x (B7-H4 or B7S1), a member of the B7 family, inhibits in vitro T cell proliferation and cytokine production by binding to an unidentified receptor on activated T cells, but its in vivo function remains largely unclear. We show that B7x protein was expressed in epithelial cells of the lung, but not in lymphoid tissues. To investigate the role of B7x in the lung, we determined the susceptibility of B7x-deficient (B7x(-/-)) mice to a lethal pulmonary infection with Streptococcus pneumoniae. B7x(-/-), but not B7-H3-deficient, mice were significantly more resistant to S. pneumoniae pulmonary infection than their wild-type (Wt) counterparts. B7x(-/-) mice had significantly lower bacterial burdens and levels of inflammatory cytokines in lungs as early as 12 h postinfection. They also had milder immunopathology that was localized in alveolar spaces, whereas Wt mice had severe inflammation that was perivascular. Control of infection in B7x(-/-) mice was associated with a marked increase in activated CD4 and CD8 T cells and fewer neutrophils in lungs, whereas the susceptible Wt mice had the opposite cellular profile. In B7x(-/-)Rag1(-/-) mice that lack T cells, reduction in bacterial burden was no longer observed. Control of S. pneumoniae and the increased survival observed was specific to the lung, because systemically infected B7x(-/-) mice were not resistant to infection. These data indicate that lung-expressed B7x negatively regulates T cells, and that in its absence, in B7x(-/-) mice, an enhanced T cell response contributed to reduced lethality in a pulmonary infection model with S. pneumoniae.

During colonization of germfree mice with the total fecal microbial community of their conventionally born and raised siblings (conventionalization), the intestinal mucosal immune system initiates and maintains a balanced immune response. However, the genetic regulation of these balanced, appropriate responses to the microbiota is obscure. Here, combined analysis of germfree and conventionalized mice revealed that the major molecular responses could be detected initiating at day 4 post conventionalization, with a strong induction of innate immune functions followed by stimulation of adaptive immune responses and development and expansion of adaptive immune cells at later stages of conventionalization. This study provides a comprehensive overview of mouse developmental and immune-related cellular pathways and processes that were co-mediated by the commensal microbiota and suggests which mechanisms were involved in this reprogramming. The dynamic, region-dependent mucosal responses to the colonizing microbiota revealed potential transcriptional signatures for the control of intestinal homeostasis in healthy mice, which may help to decipher the genetic basis of pathway dysregulation in human intestinal inflammatory diseases.

We compared the specificities of two interferon-gamma release assays (IGRAs), T-SPOT®.TB (T-SPOT) and the QuantiFERON®-TB Gold In-Tube (QFT-GIT) assay, in strictly selected subjects with a low risk of tuberculosis (TB) infection in a Japanese population. Of 111 subjects who were mostly bacille Calmette-Guérin vaccinated, one was positive using both assays and 110 were negative, using international cut-off values. Although several meta-analyses report that QFT-GIT has higher specificity than T-SPOT, our study demonstrates that the specificity of both assays is equally high in a population with a truly low risk of TB infection.

Colonization of the human stomach with Helicobacter pylori is a risk factor for peptic ulceration, noncardia gastric adenocarcinoma, and gastric lymphoma. The secreted VacA toxin is an important H. pylori virulence factor that causes multiple alterations in gastric epithelial cells and T cells. Several families of vacA alleles have been described, and H. pylori strains containing certain vacA types (s1, i1, and m1) are associated with an increased risk of gastric disease, compared to strains containing other vacA types (s2, i2, and m2). Thus far, there has been relatively little study of the role of the VacA intermediate region (i-region) in toxin activity. In this study, we compared the ability of i1 and i2 forms of VacA to cause functional alterations in Jurkat cells. To do this, we manipulated the chromosomal vacA gene in two H. pylori strains to introduce alterations in the region encoding the VacA i-region. We did not detect any differences in the capacity of i1 and i2 forms of VacA to cause vacuolation of RK13 cells. In comparison to i1 forms of VacA, i2 forms of VacA had a diminished capacity to inhibit the activation of nuclear factor of activated T cells (NFAT) and suppress interleukin-2 (IL-2) production. Correspondingly, i2 forms of VacA bound to Jurkat cells less avidly than did i1 forms of VacA. These results indicate that the VacA i-region is an important determinant of VacA effects on human T cell function.

Chlamydia trachomatis L2 invasively attacks lymphatic and subepithelial tissues of the genital tract during the formation of primary lesions. This subsequently results in lymphadenopathy, and suggests a greater propensity for systemic dissemination. However, whether lymphocytes are a potential vehicle cell for the dissemination of this infection remains unknown. We therefore assessed the growth properties of C. trachomatis L2 in lymphoid Jurkat cells compared with those observed in epithelial HeLa cells. Both cells supported the growth of C. trachomatis with a similar increase in infective progenies. Enriched human-blood lymphocytes also supported the C. trachomatis growth as well as Jurkat cells. Bacteria infecting the Jurkat cells were more susceptible to antibiotics (doxycycline, azithromycin, ofloxacin) than those in HeLa cells. Of the sphingomyelin biosynthesis inhibitors tested, both myriocin and fumonisin B1 significantly inhibited bacterial growth in both cells types. A Jurkat cell mutant that impaired bacterial growth was established using ethylmethanesulfonate treatment. DNA microarray analysis with real-time reverse transcription-polymerase chain reaction revealed that the mutant cells over-expressed granzyme K gene. Immunofluorescence staining also indicated that granzyme K irregularly over-expressed among the mutant cells as compared with that of the wild cells, suggesting a possible mechanism refractory to C. trachomatis infection. Thus, we concluded that C. trachomatis L2 could infect Jurkat cells with lymphoid properties, providing a new tool for studying C. trachomatis dissemination to tissues via lymphocyte movement., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Immune evasion is essential for Brucella abortus to survive in the face of robust adaptive CD4+ T cell response. We have previously demonstrated that B. abortus can indirectly inhibit CD4+ T cells by down-regulating MHC-II expression and antigen presentation on macrophages. However, whether B. abortus is able to directly interfere with T lymphocytes is not known. We report here that B. abortus induces apoptosis of human T lymphocytes, even though invasion of T lymphocytes was low and non-replicative. The ability of heat-killed B. abortus to reproduce the same phenomenon suggested that there was a bacterial structural component involved. We demonstrated that a prototypical B. abortus outer membrane lipoprotein (l-Omp19), but not its unlipidated form, induced T lymphocyte apoptosis. Moreover, a synthetic lipohexapeptide that mimics the structure of the protein lipid moiety also induced an increase in T lymphocyte cell death, indicating that the structural component implicated in the phenomenon could be any B. abortus lipoprotein. B. abortus-induced T lymphocyte apoptosis was dependent on the secretion of TNF-α since pre-incubation of T lymphocytes with anti-TNF-α mAb inhibited the apoptosis of the cells. Overall, these results represent a new mechanism whereby B. abortus by directly inhibiting T cell-mediated responses may evade adaptive immune responses., (Copyright © 2012. Published by Elsevier Masson SAS.)

Background: Tuberculous spondylodiscitis is one the many manifestations of active tuberculosis (TB) and can result following primary infection or, more frequently, from reactivation of active TB in subjects with latent TB. Definitive diagnosis of tuberculous spondylodiscitis requires the identification of Mycobacterium tuberculosis in the biological sample following microbiological analysis., Aim: To summarize the recent advancement in the diagnosis of TB, focusing on classical and molecular microbiological procedures, providing an overview on the recent advancements in the understanding of TB pathogenesis and their implications for the immunological diagnosis, Materials and Methods: Isolation in culture of the bacilli and detection using molecular tools are the gold standards, though sensitivity of these assays is significantly lower compared to what observed for pulmonary TB, making diagnosis of spinal TB challenging., Results: The use of the interferon-gamma release assays (IGRAs) for the immunological diagnosis of TB infection could be of help and shall precede the invasive techniques, such as biopsy or surgery, required to obtain the biological sample. IGRAs measure the presence of effector T cells in the blood that can readily respond to an antigenic stimuli by secreting cytokines, and that are an indication of the presence of the bacilli in vivo. IGRAs are more sensitive and specific than the intradermic reaction of Mantoux, though both these immunological tests cannot distinguish between latent TB infection and active TB., Conclusions: A modern diagnosis of TB spondylodiscitis should rely on the use of microbiological and immunological assays and the latter could potentially be of great help in monitoring therapy effectiveness.

Staphylococcus aureus is most frequently isolated pathogen causing bloodstream infections, skin and soft tissue infections and pneumonia. Vancomycin sensitive and resistant S. aureus infection causes oxidative stress in neutrophils and lymphocytes. Lymphocyte is an important immune cell. The immune cells use reactive oxygen species (ROS) for carrying out their normal functions while an excess amount of ROS can attack cellular components that lead to cell damage. The aim of the present study was to test the protective role of nanoconjugated vancomycin against Vancomycin Sensitive S. aureus (VSSA) and Vancomycin Resistant S. aureus (VRSA) infection induced oxidative stress in T-lymphocytes. VSSA and VRSA infection were developed in Swiss mice by intraperitoneal injection of 5 × 10(6) CFU/ml bacterial solutions. Nanoconjugated vancomycin was treated to VSSA and VRSA infected mice at a dose of 100 mg/kg bw/day and 500 mg/kg bw/day, respectively for successive 10 days. Vancomycin was treated to VSSA and VRSA infected mice at similar dose, respectively, for 10 days. The result of this study reveals that in vivo VSSA and VRSA infection significantly increases the level of nitrite generation, lipid peroxidation, protein oxidation, oxidized glutathione level, DNA fragmentation, and decreases the level of reduced glutathione, antioxidant enzyme status, glutathione dependent enzymes as compared to control group; which were increased or decreased significantly near to normal in T-lymphocytes of nanoconjugated vancomycin treated group. These finding suggests the potential use and beneficial protective role of nanoconjugated vancomycin against VSSA and VRSA infection induced oxidative stress in T-lymphocytes.

With rising incidence of acquired drug resistance among life-threatening pathogens, alternative approaches to improve therapy and vaccination have taken center stage. To this end, genome-wide and pathway-specific siRNA libraries are being employed increasingly to identify genes that regulate immune responses against a number of pathogens. In this study using calcium and cysteine protease pathway-specific siRNA libraries, we identified genes that play critical roles in modulating diverse functions of dendritic cells (DCs) during Mycobacterium tuberculosis infection. Knockdown of many of these genes in the two pathways resulted in reduced bacterial burden within DCs. These included genes that regulated activation of transcription factors, ubiquitin-specific peptidases, and genes that are involved in autophagy and neddylation. Knockdown of certain genes increased the expression of IL-12p40 and surface densities of costimulatory molecules in an antigen- and receptor-specific manner. Increased IL-12p40 and costimulatory molecules on DCs also promoted the development of Th1 responses from a Th2 inducing antigen. Furthermore, modulation of autophagy and oxidative burst appeared to be one of the mechanisms by which these genes regulated survival of M. tuberculosis within DCs. Although some genes regulated specific responses, others regulated multiple responses that included IL-12 production, T cell priming, as well as intracellular survival of M. tuberculosis. Further dissection of the mechanisms such as neddylation, by which these genes regulate immune responses, would improve our understanding of host parameters that are modulated during M. tuberculosis infection.

There is growing evidence showing the potential of T-cell-based gamma interferon (IFN-γ) release assays (IGRAs) for predicting the risk of progression of Mycobacterium tuberculosis (Mtb) infection, though there is little information from tuberculosis (TB)-endemic settings. In this study, we assessed the association between the level of IFN-γ produced by T cells in response to Mtb-specific antigens and the size of skin test indurations in 505 adult individuals who were screened for latent tuberculosis infection (LTBI) using the QuantiFERON-TB Gold In Tube (QFTGIT) assay and tuberculin skin test (TST). There was a strong positive correlation between the level of IFN-γ induced by the specific antigens and the diameter of the skin indurations (Spearman's rho = 0.6, P < 0.001). Body mass index and parasitic infection were not associated with the level of IFN-γ production or the TST reaction. In linear regression analysis, the size of the skin test indurations was significantly associated with the mean level of IFN-γ [coefficient, 0.65; 95% confidence interval (CI), 0.47 to 0.82, P < 0.001]. Similarly, results from logistic regression analysis demonstrated that individuals who had skin test indurations ≥ 10 mm were 6.82 times more likely than individuals who had skin test indurations < 10 mm to have high levels of IFN-γ (i.e. positive QFTGIT result) (adjusted odd ratio = 6.82; 95% CI, 3.67 to 12.69, P < 0.001). In conclusion, the results of this study could provide indirect evidence for the prognostic use of the QFTGIT assay for progression of Mtb infection, though prospective follow-up studies are needed to provide direct evidence.

Transcription factors regulate T cell fates at every stage of development and differentiation. Members of the Foxp family of forkhead transcription factors are essential for normal T lineage development; Foxp3 is required for T regulatory cell generation and function, and Foxp1 is necessary for generation and maintenance of naïve T cells. Foxp4, an additional member of the Foxp family, is highly homologous to Foxp1 and has been shown to dimerize with other Foxp proteins. We report the initial characterization of Foxp4 in T lymphocytes. Foxp4 is expressed in both thymocytes and peripheral CD4(+) and CD8(+) T cells. We used a CD4Cre mediated approach to evaluate the cell autonomous role for Foxp4 in murine T lymphocytes. T cell development, peripheral cellularity and cell surface phenotype are normal in the absence of Foxp4. Furthermore, Foxp3(+) T regulatory cells develop normally in Foxp4 deficient animals and naïve Foxp4 deficient CD4 T cells can differentiate to inducible T regulatory cells in vitro. In wild-type T cells, expression of Foxp4 increases following activation, but deletion of Foxp4 does not affect T cell proliferative responses or in vitro effector T cell differentiation. In vivo, despite effective control of Toxoplasma gondii and acute lymphocytic choriomeningitis virus infections, effector cytokine production during antigen specific recall responses are reduced in the absence of Foxp4. We conclude that Foxp4 is dispensable for T cell development, but necessary for normal T cell cytokine recall responses to antigen following pathogenic infection.

Monocytes and T-cells are critical to the host response to acute bacterial infection but monocytes are primarily viewed as amplifying the inflammatory signal. The mechanisms of cell death regulating T-cell numbers at sites of infection are incompletely characterized. T-cell death in cultures of peripheral blood mononuclear cells (PBMC) showed 'classic' features of apoptosis following exposure to pneumococci. Conversely, purified CD3(+) T-cells cultured with pneumococci demonstrated necrosis with membrane permeabilization. The death of purified CD3(+) T-cells was not inhibited by necrostatin, but required the bacterial toxin pneumolysin. Apoptosis of CD3(+) T-cells in PBMC cultures required 'classical' CD14(+) monocytes, which enhanced T-cell activation. CD3(+) T-cell death was enhanced in HIV-seropositive individuals. Monocyte-mediated CD3(+) T-cell apoptotic death was Fas-dependent both in vitro and in vivo. In the early stages of the T-cell dependent host response to pneumococci reduced Fas ligand mediated T-cell apoptosis was associated with decreased bacterial clearance in the lung and increased bacteremia. In summary monocytes converted pathogen-associated necrosis into Fas-dependent apoptosis and regulated levels of activated T-cells at sites of acute bacterial infection. These changes were associated with enhanced bacterial clearance in the lung and reduced levels of invasive pneumococcal disease.

5-Lipoxygenase-derived products have been implicated in both the inhibition and promotion of chronic infection. Here, we sought to investigate the roles of endogenous 5-lipoxygenase products and exogenous leukotrienes during Histoplasma capsulatum infection in vivo and in vitro. 5-LO deficiency led to increased lung CFU, decreased nitric oxide production and a deficient primary immune response during active fungal infection. Moreover, H. capsulatum-infected 5-LO(-/-) mice showed an intense influx of neutrophils and an impaired ability to generate and recruit effector T cells to the lung. The fungal susceptibility of 5-LO(-/-) mice correlated with a lower rate of macrophage ingestion of IgG-H. capsulatum relative to WT macrophages. Conversely, exogenous LTB4 and LTC4 restored macrophage phagocytosis in 5-LO deficient mice. Our results demonstrate that leukotrienes are required to control chronic fungal infection by amplifying both the innate and adaptive immune response during histoplasmosis.

Aging increases susceptibility to infection, in part because thymic involution culminates in reduced naïve T-lymphocyte output. Thymic epithelial cells (TECs) are critical to ensure normal maturation of thymocytes and production of peripheral T cells. The forkhead-class transcription factor, encoded by FoxN1, regulates development, differentiation, and function of TECs, both in the prenatal and postnatal thymus. We recently showed that expression of FoxN1, by keratin 14 (K14)-expressing epithelial cells is essential for maintenance of thymic medullary architecture, and deletion of FoxN1 in K14 promoter-driven TECs inhibited development of mature TECs and reduced the number of total thymocytes. These findings are reminiscent of changes observed during normal thymic aging. In the current report, we compared the effects of K14-driven FoxN1 deletion on peripheral T cell function in response to influenza virus infection with those associated with normal aging in a mouse model. FoxN1-deleted mice had reduced numbers of peripheral CD62L+CD44- naïve T-cells. In addition, during influenza infection, these animals had reduced antigen-specific CD8+ T-cell and IgG responses to influenza virus, combined with increased lung injury, weight loss and mortality. These findings paralleled those observed in aged wild type mice, providing the first evidence that K14-mediated FoxN1 deletion causes changes in T-cell function that mimic those in aging during an immune response to challenge with an infectious agent.

Due to drawbacks of live attenuated vaccines, much more attention has been focused on screening of Brucella protective antigens as subunit vaccine candidates. Brucella is a facultative intracellular bacterium and cell mediated immunity plays essential roles for protection against Brucella infection. Identification of Brucella antigens that present T-cell epitopes to the host could enable development of such vaccines. In this study, 45 proven or putative pathogenesis-associated factors of Brucella were selected according to currently available data. After expressed and purified, 35 proteins were qualified for analysis of their abilities to stimulate T-cell responses in vitro. Then, an in vitro gamma interferon (IFN-γ) assay was used to identify potential T-cell antigens from B. abortus. In total, 7 individual proteins that stimulated strong IFN-γ responses in splenocytes from mice immunized with B. abortus live vaccine S19 were identified. The protective efficiencies of these 7 recombinant proteins were further evaluated. Mice given BAB1&#95;1316 (CobB) or BAB1&#95;1688 (AsnC) plus adjuvant could provide protection against virulent B. abortus infection, similarly with the known protective antigen Cu-Zn SOD and the license vaccine S19. In addition, CobB and AsnC could induce strong antibodies responses in BALB/c mice. Altogether, the present study showed that CobB or AsnC protein could be useful antigen candidates for the development of subunit vaccines against brucellosis with adequate immunogenicity and protection efficacy.

The healthy gut tolerates very large numbers of diverse bacterial species belonging mainly to the Bacteroidetes and Firmicutes phyla. These bacteria normally coexist peacefully with the gut and help maintain immune homeostasis and tolerance. The mechanisms promoting tolerance affect various cell populations, including the epithelial cells lining the gut, resident dendritic cells (DCs), and gut-homing T cells. Gut bacteria also influence multiple signaling pathways from Toll-like receptors to nuclear factor κB and regulate the functionality of DCs and T cells. Several bacterial species have been identified that promote T-cell differentiation, in particular T-helper 17 and T-regulatory cells. Insight into the molecular mechanisms by which bacteria mediate these effects will be very important in identifying new ways of treating intestinal and extra-intestinal immune-mediated diseases. These diseases are increasing dramatically in the human population and require new treatments. It may be possible in the future to identify specific bacterial species or strains that can correct for T-cell imbalances in the gut and promote immune homeostasis, both locally and systemically. In addition, new information describing microbial genomes affords the opportunity to mine for functional genes that may lead to new generation drugs relevant to a range of inflammatory disease conditions., (© 2011 John Wiley & Sons A/S.)

Pulmonary tuberculosis (TB), caused by the intracellular bacteria Mycobacterium tuberculosis, is a worldwide disease that continues to kill more than 1.5 million people every year worldwide. The accumulation of lymphocytes mediates the formation of the tubercle granuloma in the lung and is crucial for host protection against M.tuberculosis infection. However, paradoxically the tubercle granuloma is also the basis for the immunopathology associated with the disease and very little is known about the regulatory mechanisms that constrain the inflammation associated with the granulomas. Lipocalin 2 (Lcn2) is a member of the lipocalin family of proteins and binds to bacterial siderophores thereby sequestering iron required for bacterial growth. Thus far, it is not known whether Lcn2 plays a role in the inflammatory response to mycobacterial pulmonary infections. In the present study, using models of acute and chronic mycobacterial pulmonary infections, we reveal a novel role for Lcn2 in constraining T cell lymphocytic accumulation and inflammation by inhibiting inflammatory chemokines, such as CXCL9. In contrast, Lcn2 promotes neutrophil recruitment during mycobacterial pulmonary infection, by inducing G-CSF and KC in alveolar macrophages. Importantly, despite a common role for Lcn2 in regulating chemokines during mycobacterial pulmonary infections, Lcn2 deficient mice are more susceptible to acute M.bovis BCG, but not low dose M.tuberculosis pulmonary infection.

The prevalence of gastric cancer is associated with several factors including geographical location, diet, and genetic background of the host. However, it is evident that infection with Helicobacter pylori (H. pylori) is crucial for the development of the disease. Virulence of the bacteria is also important in modulating the risk of the disease. After infection, H. pylori gains access to the gastric mucosa and triggers the production of cytokines that promote recruitment of inflammatory cells, probably involved in tissue damage. Once the infection is established, a cascade of inflammatory steps associated with changes in the gastric epithelia that may lead to cancer is triggered. H. pylori-induced gastritis and H. pylori-associated gastric cancer have been the focus of extensive research aiming to discover the underlying mechanisms of gastric tissue damage. This research has led to the association of host genetic components with the risk of the disease. Among these is the presence of single nucleotide polymorphisms (SNPs) in several genes, including cytokine genes, which are able to differentially modulate the production of inflammatory cytokines and then modulate the risk of gastric cancer. Interestingly, the frequency of some of these SNPs is different among populations and may serve as a predictive factor for gastric cancer risk within that specific population. However, the role played by other genetic modifications should not be minimized. Methylation of gene promoters has been recognized as a major mechanism of gene expression regulation without changing the primary structure of the DNA. Most DNA methylation occurs in cytosine residues in CpG dinucleotide, but it can also be found in other DNA bases. DNA methyltransferases add methyl groups to the CpG dinucleotide, and when this methylation level is too high, the gene expression is turned off. In H. pylori infection as well as in gastric cancer, hypermethylation of promoters of genes involved in cell cycle control, metabolism of essential nutrients, and production of inflammatory mediators, among others, has been described. Interestingly, DNA changes like SNPs or mutations can create CpG sites in sequences where transcription factors normally sit, affecting transcription.In this chapter, we review the literature about the role of SNPs and methylation on H. pylori infection and gastric cancer, with big emphasis to the H. pylori role in the development of the disease due to the strong association between both.