Invariant NKT cells sustain specific B cell responses and memory

摘要

Invariant natural killer T (iNKT) cells are innate-like lymphocytes recognizing CD1d-restricted glycolipid antigens, such as α-galactosylceramide (αGC). We assessed whether iNKT cells help B lymphocyte responses and found that mice immunized with proteins and αGC develop antibody titers 1-2 logs higher than those induced by proteins alone. Activation of iNKT cells enhances protection against infections such as influenza and elicits higher frequencies of memory B cells and higher antibody responses to booster immunizations. Protein vaccination with αGC, but not with conventional adjuvants, elicits IgG responses in mice lacking MHC class Ⅱ molecules, demonstrating that iNKT cells can substitute for CD4~+ T cell help to B cells. Interestingly, the decay of circulating antibodies is faster in mice lacking iNKT cells. These findings point to a homeostatic role for iNKT cells on critical features of the antibody response such as immunity and B cell memory.