NK cell-deficient mice develop a Th1-like response but fail to mount an efficient antigen-specific IgG2a antibody response.

NK cells have been shown to play a role in the modulation of B cell differentiation and Ab production. Using a novel murine model of NK cell deficiency, we analyzed the in vivo role of NK cells in the regulation of Ag-specific Ab production. After immunization with OVA or keyhole limpet hemocyanin in CFA, NK cell-deficient (NK-T+) mice developed an efficient Th1 response and produced significant levels of IFN-gamma but displayed markedly reduced or absent Ag-specific IgG2a production. There were no differences in the levels of Ag-specific IgG, IgG1, and IgG2b between NK-T+ and NK+T+ mice. Furthermore, NK cell-reconstituted, NK+T+ (tgepsilon26Y) mice produced significant amounts of Ag-specific IgG2a after immunization with OVA. These results indicate that NK cells are involved in the induction of Ag-specific IgG2a production in vivo. Moreover, they also demonstrate that the lack of Ag-specific IgG2a Ab production in NK-T+ mice is not associated with the impaired Th1 response and IFN-gamma production.