IFNγ-Induced MHC Class II Expression on Islet Endothelial Cells Is an Early Marker of Insulitis but Is Not Required for Diabetogenic CD4+ T Cell Migration

Diabetogenic T cells infiltrate the pancreatic islets by transmigrating across the microcapillaries residing close to, or within, the pancreatic islets. Deficiency in IFNγ signaling prevents efficient migration of T cells into the pancreatic islets, but the IFNγ-regulated molecules that mediate this are uncertain. Homing of autoreactive T cells into target tissues may require antigen specificity through presentation of cognate antigen by MHC expressed on the vascular endothelium. We investigated the hypothesis that IFNγ promotes the migration of islet antigen-specific CD4+ T cells by upregulating MHC class II on islet endothelial cells (IEC), thereby providing an antigen-specific signal for islet infiltration. Upon IFNγ stimulation, MHC class II, which is not constitutively expressed on IEC, was induced. IFNγ-dependent upregulation of MHC class II was detected in IEC isolated from prediabetic NOD mice at the earliest stages of insulitis, before other markers of inflammation were present. Using a CD4+ T cell-mediated adoptive transfer model of autoimmune diabetes we observed that even though diabetes does not develop in recipient mice lacking IFNγ receptors, mice with MHC class II-deficient IEC were not protected from disease. Thus, IFNγ-regulated molecules, but not MHC class II or antigen presentation by IECs is required for the early migration of antigen-specific CD4+ T cells into the pancreatic islets

α/β–T Cell Receptor (TCR)+CD4−CD8− (NKT) Thymocytes Prevent Insulin-dependent Diabetes Mellitus in Nonobese Diabetic (NOD)/Lt Mice by the Influence of Interleukin (IL)-4 and/or IL-10

We have previously shown that nonobese diabetic (NOD) mice are selectively deficient in α/β-T cell receptor (TCR)+CD4−CD8− NKT cells, a defect that may contribute to their susceptibility to the spontaneous development of insulin-dependent diabetes mellitus (IDDM). The role of NKT cells in protection from IDDM in NOD mice was studied by the infusion of thymocyte subsets into young female NOD mice. A single intravenous injection of 106 CD4−/lowCD8− or CD4−CD8− thymocytes from female (BALB/c × NOD)F1 donors protected intact NOD mice from the spontaneous onset of clinical IDDM. Insulitis was still present in some recipient mice, although the cell infiltrates were principally periductal and periislet, rather than the intraislet pattern characteristic of insulitis in unmanipulated NOD mice. Protection was not associated with the induction of “allogenic tolerance” or systemic autoimmunity. Accelerated IDDM occurs after injection of splenocytes from NOD donors into irradiated adult NOD recipients. When α/β-TCR+ and α/β-TCR− subsets of CD4−CD8− thymocytes were transferred with diabetogenic splenocytes and compared for their ability to prevent the development of IDDM in irradiated adult recipients, only the α/β-TCR+ population was protective, confirming that NKT cells were responsible for this activity. The protective effect in the induced model of IDDM was neutralized by anti–IL-4 and anti–IL-10 monoclonal antibodies in vivo, indicating a role for at least one of these cytokines in NKT cell-mediated protection. These results have significant implications for the pathogenesis and potential prevention of IDDM in humans

Anti-CD3 treatment up-regulates programmed cell death protein-1 expression on activated effector T cells and severely impairs their inflammatory capacity

T cells play a key role in the pathogenesis of type 1 diabetes, and targeting the CD3 component of the T-cell receptor complex provides one therapeutic approach. Anti-CD3 treatment can reverse overt disease in spontaneously diabetic non-obese diabetic mice, an effect proposed to, at least in part, be caused by a selective depletion of pathogenic cells. We have used a transfer model to further investigate the effects of anti-CD3 treatment on green fluorescent protein (GFP)+ islet-specific effector T cells in vivo. The GFP expression allowed us to isolate the known effectors at different time-points during treatment to assess cell presence in various organs as well as gene expression and cytokine production. We find, in this model, that anti-CD3 treatment does not preferentially deplete the transferred effector cells, but instead inhibits their metabolic function and their production of interferon-γ. Programmed cell death protein 1 (PD-1) expression was up-regulated on the effector cells from anti-CD3-treated mice, and diabetes induced through anti-PD-L1 antibody could only be reversed with anti-CD3 antibody if the anti-CD3 treatment lasted beyond the point when the anti-PD-L1 antibody was washed out of the system. This suggests that PD-1/PD-L1 interaction plays an important role in the anti-CD3 antibody mediated protection. Our data demonstrate an additional mechanism by which anti-CD3 therapy can reverse diabetogenesis.This work was funded by grants from the National Centre for the Replacement, Refinement and Reduction of Animals in research (NC3Rs) (NC/M001083/1) (MW), Diabetes UK (BDA 13/0004785) (AC), Diabetes Research and Wellness (SCA/OF/12/13) (AC), European Research Council 7th Frame Programme (health-f5-2009-241883) (AC and HW), Britain Israel Research and Academic Exchange Partnership (BIRAX) (02BX12ACYD) (AC), and ERC advanced investigator grant 339402 (HW) and pump priming funding from the Cambridge University Isaac Newton trust