In vivo and in vitro analyses of α-galactosylceramide uptake by conventional dendritic cell subsets using its fluorescence-labeled derivative

Conventional dendritic cells (cDCs) present α-galactosylceramide (αGC) to invariant natural killer T (iNKT) cells through CD1d. Among cDC subsets, CD8⁺ DCs efficiently induce IFN-γ production in iNKT cells. Using fluorescence-labeled αGC, we showed that CD8⁺ DCs incorporated larger amounts of αGC and kept it intact longer than CD8^- DCs. Histological analyses revealed that Langerin⁺CD8⁺ DCs in the splenic marginal zone, which was the unique equipment to capture blood-borne antigens, preferably incorporated αGC, and the depletion of Langerin⁺ cells decreased IFN-γ and IL-12 production in response to αGC. Furthermore, splenic Langerin⁺CD8⁺ DCs expressed more membrane-bound CXCL16, which possibly anchored iNKT cells in the marginal zone, than CD8^- DCs. Collectively, it is suggested that the cellular properties and localization of CD8⁺ DCs are important for stimulation of iNKT cells by αGC.