Membrane-bound TGF-β or other this website contact-dependent factors have been shown to be the main mediators of Foxp3+ Treg action in direct co-culture experiments 34, 35. Previous studies using type I diabetes and chronic colitis models have suggested the possible involvement of contact-dependent mechanisms in NKT-mediated immune suppression 25, 32, although these reports did not evaluate the specific effects on Th17 differentiation. It is known that NKT cells express several inhibitory molecules on their surface, and these molecules are upregulated when NKT cells are activated 18, 19. We are currently attempting to identify the responsible

molecules expressed on the NKT cells and blocking antibodies against CD40L, 4-1BB, 4-1BBL, CTLA-4, Fas, 2B4, NKG2D, GITR, and PD-1 failed to abrogate NKT inhibitory effects on PLX4720 Th17 differentiation. Therefore, additional experiments are needed to find out the target molecules involved in NKT:CD4+ T-cell interaction

and we are also examining the role of APC in the NKT cell-mediated inhibitory process. The regulatory role of NKT cells on TH differentiation was confirmed in vivo using an EAU model. CD1d−/− and Jα18−/− mice displayed a more severe disease phenotype compared with WT mice (Fig. 5A and B). Upon closer examination of the data, the disease severity appears milder in Jα18−/− mice compared with CD1d−/− mice, and thus we cannot completely rule out the effect of type 2 NKT cells present in Jα18−/− mice. However, as the difference between CD1d−/− and Jα18−/− was not statistically significant (p=0.203), we used CD1d−/− mice in the majority of the following experiments. The adoptive transfer of WT NKT cells decreased the degree of uveitis in CD1d−/− mice to that of WT mice (Fig. 5H). Moreover, the profile of disease regulation following adoptive transfer of NKT cells from different cytokine-deficient mice (Fig. 5H) paralleled the inhibitory effects of cytokine-deficient NKT cells on Th17 differentiation in vitro (Fig. RVX-208 2A and B), which is consistent with recent reports demonstrating that experimental uveitis induced following immunization with uveitogenic antigens was predominantly mediated through Th17 effector

pathways 15, 17. Grajewski et al. also reported the regulatory role of invariant NKT cells in experimental uveitis 36. In this report, however, CD1d-deficient mice did not show enhanced susceptibility to uveitis. In contrast to their observation, invariant NKT cell-deficient mice, both CD1d−/− and Jα18−/− mice, revealed great increases in disease severity in our study. Discrepancies might lie on the different antigen types used: we used human IRBP peptide fragments 1–20, which could discriminate increased pathogenesis between IFN-γ−/− and WT B6 mice 37. The relative lack of IL-10 induction with IRBP peptides 1–20 37 compared with the IRBP protein used in a previous study 36 could explain the increased sensitivity in disease pathogenesis of NKT cell-deficient mice in our experiments.