Invariant NKT cells regulate experimental autoimmune uveitis through inhibition of Th17 differentiation.

Although NKT cells have been implicated in diverse immunomodulatory responses, the effector mechanisms underlying the NKT cell-mediated regulation of pathogenic T helper cells are not well understood. Here, we show that invariant NKT cells inhibited the differentiation of CD4(+) T cells into Th17 cells both in vitro and in vivo. The number of IL-17-producing CD4(+) T cells was reduced following co-culture with purified NK1.1(+) TCR(+) cells from WT, but not from CD1d(-/-) or Jα18(-/-) , mice. Co-cultured NKT cells from either cytokine-deficient (IL-4(-/-) , IL-10(-/-) , or IFN-γ(-/-) ) or WT mice efficiently inhibited Th17 differentiation. The contact-dependent mechanisms of NKT cell-mediated regulation of Th17 differentiation were confirmed using transwell co-culture experiments. On the contrary, the suppression of Th1 differentiation was dependent on IL-4 derived from the NKT cells. The in vivo regulatory capacity of NKT cells on Th17 cells was confirmed using an experimental autoimmune uveitis model induced with human IRBP(1-20) (IRBP, interphotoreceptor retinoid-binding protein) peptide. NKT cell-deficient mice (CD1d(-/-) or Jα18(-/-) ) demonstrated an increased disease severity, which was reversed by the transfer of WT or cytokine-deficient (IL-4(-/-) , IL-10(-/-) , or IFN-γ(-/-) ) NKT cells. Our results indicate that invariant NKT cells inhibited autoimmune uveitis predominantly through the cytokine-independent inhibition of Th17 differentiation.