Both activation of NKT cells by cognate self ligands (1a) and IL-12-mediated signaling from dendritic cells induced by pathogens (1b) are required for the initial steps of protective immunity. These activation events efficiently induce IFN-γ production from NKT cells, which subsequently activates other cell types, such as T cells (2a) in the adaptive immune system as well as NK cells and macrophages (2d) in the innate immune system. Activated NKT cells show regulatory function (2b) and direct cytotoxicity (2c)⁶. IL-12R, IL-12 receptor; DC, dendritic cell; TLR, toll-like receptor.

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