Induction of CD4+ T-cell-independent immunoglobulin responses by inactivated influenza virus

Through cognate interaction between antigen-specific B-cell and CD4(+) alpha beta T cells, the CD4(+) crp T cells secrete cytokines that initiate immunoglobulin (Ig) class switching from IgM to IgG, In this study, me show that formalin-inactivated influenza PR8 virus induces virus-specific IgM and Ige responses in the absence of CD4(+) T cells and that all four subclasses of IgG are produced. The immunized CD4(-)deficient mice were also found to be completely protected against lethal infection with live, pathogenic influenza virus. The ability of CD IC T-cell-deficient mice to generate these IgG responses was not found to be impaired when these mice were depleted of CD8(+) T cells with an anti-CD8 monoclonal antibody. In contrast, alpha beta T-cell-deficient mice (TCR beta(-/-)) were not found to produce significant amounts of Ige upon immunization with formalin-inactivated PR8 virus. These results suggest that CD4(-) CD8(-) double-negative ap T cells are playing a role in regulating Ig class switching in the absence of CD4(+) T cells.