Characterization of the immature dendritic cells and cytotoxic cells both expanded after activation of invariant NKT cells with α-galactosylceramide in vivo

Invariant natural killer T (iNKT) cells can perform multiple functions characteristic of both innate and acquired immunity. Activation of iNKT cells in vivo by repeated α-GalCer injections can induce immune tolerance, but the mechanisms responsible for such immunoregulation remain unclear. We prepared α-GalCer-liposomes, a single injection of which into mice resulted in the expansion of splenic CD11clowCD45RBhigh cells, which consists of two populations, CD180+ and CD49b+. Expansion of these cells was not observed in α-GalCer-liposome-treated mice deficient in IL-10 or iNKT cells. MHC and co-stimulatory molecules were down-regulated in CD11clowCD180+ cells compared with conventional dendritic cells (cDCs), suggesting that the former possess characteristics of immature DCs. Meanwhile, the CD11clowCD49b+ cells expressed IL-10 and Ctla4, and possessed greater lytic activity than resting NK cells. These observations suggest that both immature DCs (CD11clowCD180+) and cytotoxic cells (CD11clowCD49b+) might be expanded by α-GalCer-activated iNKT cells and could therefore be involved in immune tolerance.