Figure 2.

Diagram of iNKT cells in hygiene hypothesis. iNKT cells can be activated by glycolipids from microbes and parasites, which bind to CD1 molecules on antigen-presenting cell (APC). Activated iNKT cells secrete a broad range of effector cytokines. They also mediate cytotoxic activity, possibly involving both perforin/granzyme B and Fas/FasL pathways. Moreover, iNKT cells may cross talk with Treg, Th17, ILC, and Th1/2 subsets via secreted cytokines or direct contact. iNKT cells may exert their immunomodulatory effects in hygiene hypothesis through the above combined and other effects.