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Vγ6

Viral infection is a putative causal factor for the development of type 1 diabetes, but the exact pathogenic mechanism of virus-induced diabetes (VID) remains unclear. Here, to identify the critical factors that regulate VID, we analyzed encephalomyocarditis D (EMC-D) VID-sensitive DBA/2 mice in comparison with resistant B6 mice. EMC-D virus-induced cell death occurred more frequently in DBA/2 β-cells than in B6 β-cells with 100U/ml IFN-β priming in vitro. We therefore purified β-cells using flow cytometry from mice two days after EMC-D virus infection and subjected them to microarray analysis. As a results, innate immune response pathway was found to be enriched in B6 β-cells. The signal transducer and activator of transcription 2 (Stat2) gene interacted with genes in the pathway. Stat2 gene expression levels were lower in DBA/2 mice than in B6 mice, restrictive to β-cells. Moreover, administration of IFN-β failed to upregulate Stat2 gene in DBA/2 β-cells than in those of B6 in vivo. The viral titer significantly increased only in the DBA/2 pancreas. Thus, these provided data suggest that impaired upregulation of Stat2 gene restrictive to β-cells at the early stage of infection is responsible for VID development in DBA/2 mice.

Although murine γδ T cells are largely considered innate immune cells, they have recently been reported to form long-lived memory populations. Much remains unknown about the biology and specificity of memory γδ T cells. Here, we interrogated intestinal memory Vγ4 Vδ1 T cells generated after foodborne Listeria monocytogenes (Lm) infection to uncover an unanticipated complexity in the specificity of these cells. Deep TCR sequencing revealed that a subset of non-canonical Vδ1 clones are selected by Lm infection, consistent with antigen-specific clonal expansion. Ex vivo stimulations and in vivo heterologous challenge infections with diverse pathogenic bacteria revealed that Lm-elicited memory Vγ4 Vδ1 T cells are broadly reactive. The Vγ4 Vδ1 T cell recall response to Lm, Salmonella enterica serovar Typhimurium (STm) and Citrobacter rodentium was largely mediated by the γδTCR as internalizing the γδTCR prevented T cell expansion. Both broadly-reactive canonical and pathogen-selected non-canonical Vδ1 clones contributed to memory responses to Lm and STm. Interestingly, some non-canonical γδ T cell clones selected by Lm infection also responded after STm infection, suggesting some level of cross-reactivity. These findings underscore the promiscuous nature of memory γδ T cells and suggest that pathogen-elicited memory γδ T cells are potential targets for broad-spectrum anti-infective vaccines.

Innate γδ T cells expressing Vγ6 produce IL-17A at an early stage following infection with Mycobacterium bovis Bacillus Calmette-Guérin (BCG). In this study, we used IL-21 receptor knockout (IL-21R KO) mice and IL-21-producing recombinant BCG mice (rBCG-Ag85B-IL-21) to examine the role of IL-21 in the regulation of IL-17A-producing innate γδ T-cell response following BCG infection. IL-17A-producing Vγ6+ γδ T cells increased in the peritoneal cavity of IL-21R KO mice more than in wild type mice after BCG infection. In contrast, the number of IL-17A-producing Vγ6+ γδ T cells was significantly lower after inoculation with rBCG-Ag85B-IL-21 compared with control rBCG-Ag85B. Notably, exogenous IL-21 selectively induced apoptosis of IL-17A-producing Vγ6+ γδ T cells via Bim. Thus, these results suggest that IL-21 acts as a potent inhibitor of a IL-17A-producing γδ T-cell subset during BCG infection.

Interleukin 21 (IL-21) is a pleiotropic common cytokine receptor γ chain cytokine that promotes the effector functions of NK cells and CD8+ T cells and inhibits CD8+ T cell exhaustion during chronic infection. We found that the absolute number of short-lived effector CD8+ T cells (SLECs) (KLRG1high CD127low) decreased significantly in IL-21 receptor-deficient (IL-21R−/−) mice during Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection.

Heat-killed Lactobacillus plantarum strain L-137 (HK L-137) is a more potent inducer of interleukin (IL)-12 than other heat-killed Lactobacillus strains. To elucidate the mechanism involved in this IL-12p40 induction, we compared HK L-137 with heat-killed L. plantarum strain JCM1149 (HK JCM1149) by nuclear magnetic resonance and mass spectrometry. Results showed that HK L-137 contained lipoteichoic acid (LTA) with a chemical structure similar to that of JCM1149, except for a lower degree of glucosyl substitution in the poly(glycerol phosphate) backbone. Lysozyme sensitivity and electrophoretic moiety analysis revealed that HK L-137 exposed more LTA on its cell surface than HK JCM1149. Phagocytosis of HK L-137 by splenic adherent cells was significantly greater than that of HK JCM1149. Anti-LTA antibody and anti-scavenger receptor-A (SR-A) antibody selectively inhibited phagocytosis of HK L-137, as well as IL-12p40 production, by splenic adherent cells. Thus, a higher efficiency of phagocytosis of HK L-137 via SR-A for LTA is responsible for the potent IL-12p40 induction.

Background Klebsiella pneumoniae frequently causes life-threatening infection in children. Interleukin 17A (IL-17A) is known to be involved in protection against K. pneumoniae infection through activation of neutrophils. Methods and results We found that IL-17A-producing γδ T cells existed more frequently in younger mice on examination of IL-17A-producing lymphocytes in the lung of naive mice at various ages. We hence compared the protective role of IL-17A-producing γδ T cells against pulmonary K. pneumoniae infection in young (3 weeks old) and adult (8-12 weeks old) mice. IL-17A-deficient mice were susceptible to K. pneumonia regardless of age. Cγ-, Vγ4/6-, or Vδ1-deficient mice were susceptible to K. pneumonia at young age, while interleukin 23p19 (IL-23p19)-deficient mice were susceptible at adult age. IL-17A-producing Vγ1-Vγ4- γδ T cells expressing canonical Vγ6/Vδ1 genes were dominant over IL-17A-producing Vγ4+ γδ T cells in the lungs of young mice after infection. The IL-17A-producing Vγ1-Vγ4- γδ T cells expressed an activation marker, CD69, and proliferated in an IL-23-independent manner, while the IL-17A-producing Vγ4+ γδ T cells expressing IL-23 receptor but no CD69 proliferated in IL-23-dependent manner. Conclusions These results suggest that 2 types of IL-17A-producing γδ T cells are activated for host defense against K. pneumoniae infection by IL-23-dependent or independent mechanism.

Interleukin 7 (IL-7) has an important function in the development and maintenance of IL-17A+ γδ T cells. We here constructed a recombinant Mycobacterium bovis bacillus Calmette-Guerin expressing antigen 85B (Ag85B)-IL-7 fusion protein (rBCG-Ag85B-IL-7). The Ag85B-IL-7 fusion protein and IL-7 were detected in the bacterial lysate of rBCG-Ag85B-IL-7. rBCG-Ag85B-IL-7 was the same in number as control rBCG expressing Ag85B (rBCG-Ag85B) in the lung at the early stage after intravenous inoculation, whereas the numbers of IL-17A+ γδ T cells and Ag-specific Th1 cells were significantly higher in the lungs of mice inoculated with rBCG-Ag85B-IL-7 than those inoculated with rBCG-Ag85B. The Ag-specific Th1 cell response was impaired in mice lacking IL-17A+ γδ T cells after inoculation with rBCG-Ag85B-IL-7. Thus, rBCG-Ag85B-IL-7 increases the pool size of IL-17A+ γδ T cells, which subsequently augment the Th1 response to mycobacterial infection.

Notch signaling is an important regulator for the development and function of both αβ and γδ T cells, whereas roles of Notch signaling in T cell maintenance remain unclear. We reported previously that the Notch–Hes1 pathway was involved in the intrathymic development of naturally occurring IL-17–producing (IL-17+) γδ T cells. To gain insight into additional roles for the Notch axis in the homeostasis of γδ T cells, we performed a genome-wide analysis of Notch target genes and identified the novel promoter site of IL-7Rα driven by the Notch–RBP-Jκ pathway. Constitutive Notch signaling had the potential to induce IL-7Rα expression on γδ T cells in vivo, as well as in vitro, whereas conditional deletion of RBP-Jκ abrogated IL-7Rα expression, but not Hes1 expression, by γδ T cells and selectively reduced the pool size of IL-7Rαhigh IL-17+ γδ T cells in the periphery. In the absence of IL-7Rα–mediated signaling, IL-17+ γδ T cells were barely maintained in adult mice. Addition of exogenous IL-7 in vitro selectively expanded IL-17+ γδ T cells. Thus, our results revealed a novel role for the Notch–RBP-Jκ–IL-7Rα axis that is independent of Hes1 for homeostasis of IL-17+ γδ T cells.