In Mdr2 mice, we found development of liver fibrosis and inflammation to require hepatic activation of γδ TCR cells and production of IL17 mediated by exposure to L gasseri. This pathway appears to contribute to development of cholestatic liver disease in patients.

Chronic liver disease mediated by activation of hepatic stellate cells (HSCs) leads to liver fibrosis. Here, we postulated that the immune regulatory properties of HSCs might promote the profibrogenic activity of B cells. Fibrosis is completely attenuated in carbon tetrachloride (CCl4)-treated B cell deficient μMT mice showing that B cells are required. The retinoic acid produced by HSCs augmented B cell survival, plasma cell marker CD138 expression, and IgG production. These activities were reversed following the addition of the retinoic acid inhibitor, LE540. Transcriptional profiling of fibrotic liver B cells revealed an increased expression of genes related to NF-κB activation, proinflammatory cytokine production and CD40 signaling suggesting that these B cells are activated and may be acting as inflammatory cells. Biological validation experiments also revealed increased activation (CD44 and CD86 expressions), constitutive IgG production and secretion of the proinflammatory cytokines TNF-α, MCP-1 and MIP1-α. Likewise targeted deletion of B-cell-intrinsic MyD88 signaling, an innate adaptor with involvement in RA signaling, resulted in reduced infiltration of migratory CD11c+ dendritic cells and Ly6C++ monocytes, and hence reduced liver pathology. Conclusion Our findings demonstrate that liver fibrosis occurs through a mechanism of HSC-mediated augmentation of innate B cell activity and highlight B cells as an important ‘first responders’ of the intrahepatic immune environment.

GITR is a costimulatory receptor currently undergoing phase I clinical trials. Efficacy of anti-GITR therapy in syngeneic mouse models requires regulatory T-cell depletion and CD8 T-cell costimulation. It is increasingly appreciated that immune cell proliferation and function are dependent on cellular metabolism. Enhancement of diverse metabolic pathways leads to different immune cell fates. Little is known about the metabolic effects of GITR agonism; thus, we investigated whether costimulation via GITR altered CD8 T-cell metabolism. We found activated, GITR-treated CD8 T cells upregulated nutrient uptake, lipid stores, glycolysis, and oxygen consumption rate (OCR) Using MEK, PI3Kδ, and metabolic inhibitors, we show increased metabolism is required, but not sufficient, for GITR antibody (DTA-1)-induced cellular proliferation and IFNγ production. In an model of PD-L1-induced CD8 T-cell suppression, GITR agonism alone rescued cellular metabolism and proliferation, but not IFNγ production; however, DTA-1 in combination with anti-PD-1 treatment increased IFNγ production. In the MC38 mouse tumor model, GITR agonism significantly increased OCR and IFNγ and granzyme gene expression in both tumor and draining lymph node (DLN) CD8 T cells , as well as basal glycolysis in DLN and spare glycolytic capacity in tumor CD8 T cells. DLN in GITR-treated mice showed significant upregulation of proliferative gene expression compared with controls. These data show that GITR agonism increases metabolism to support CD8 T-cell proliferation and effector function , and that understanding the mechanism of action of agonistic GITR antibodies is crucial to devising effective combination therapies..

Chronic hepatitis C virus (HCV) infection is characterized by exhaustion of virus-specific T-cells and stable viremia. Pregnancy is an exception. Viremia gradually climbs during gestation but sometimes declines sharply in the months following delivery. Here, we demonstrated that postpartum HCV control was associated with enhanced virus-specific T-cell immunity. Women with viral load declines of at least 1 log 10 between the third trimester and 3-mo postpartum exhibited HCV-specific T-cell responses of greater breadth (P = 0.0052) and magnitude (P = 0.026) at 3-mo postpartum than women who failed to control viremia. Moreover, viral dynamics were consistent in women after consecutive pregnancies, suggesting genetic underpinnings. We therefore searched for genetic associations with human leukocyte antigen (HLA) alleles and IFN-λ3 gene (IFNL3) polymorphisms that influence HCV infection outcome. Postpartum viral control was associated with the IFNL3 rs12979860 genotype CC (P = 0.045 at 6 mo) that predicts a positive response to IFN-based therapy. Suppression of virus replication after pregnancy was also strongly influenced by the HLA class II DPB1 locus. HLA-DPB1 alleles are classified by high and low patterns of expression. Carriage of at least one high-expression HLA-DPB1 allele predicted resurgent virus-specific T-cell immunity and viral control at 3-mo postpartum (P = 0.0002). When considered together in multivariable analysis, IFNL3 and HLA-DPB1 independently affected viral control at 3-and 6-mo postpartum. Together, these findings support a model where spontaneous control of HCV such as sometimes follows pregnancy is governed by genetic polymorphisms that affect type III IFN signaling and virus-specific cellular immune responses.hepatitis C virus | pregnancy | T-cell | IFNL3 | HLA-DPB1

Maternal innate and adaptive immune responses are modulated during pregnancy to concurrently defend against infection and tolerate the semiallogeneic fetus. The restoration of these systems after childbirth is poorly understood. We reasoned that enhanced innate immune activation may extend beyond gestation while adaptive immunity recovers. To test this hypothesis, the transcriptional profiles of total peripheral blood mononuclear cells following delivery in healthy women were compared with those of nonpregnant control subjects. Interestingly, interferon-stimulated genes (ISGs) encoding proteins such as IFIT1, IFIT2, and IFIT3, as well as signaling proteins such as STAT1, STAT2, and MAVS, were enriched postpartum. Antiviral genes were primarily expressed in CD14 + cells and could be stratified according to genetic variation at the interferon-λ3 gene (IFNL3, also named IL28B) SNP rs12979860. Antiviral gene expression was sustained beyond 6 mo following delivery in mothers with a CT or TT genotype, but resembled baseline nonpregnant control levels following delivery in mothers with a CC genotype. CT and TT IFNL3 genotypes have been associated with persistent elevated ISG expression in individuals chronically infected with hepatitis C virus. Together, these data suggest that postpartum, the normalization of the physiological rheostat controlling IFN signaling depends on IFNL3 genotype. postpartum | CD14 | interferon | innate immunity | antiviral genes