γδ T cells modulate humoral immunity against Plasmodium berghei infection.

It is unclear whether γδ T cells are involved in humoral immunity against Plasmodium infection. Here, we show that B-cell-immunodeficient mice and γδ T-cell-deficient mice were incapable of protecting against Plasmodium berghei XAT parasites. γδ T-cell-deficient mice developed reduced levels of antigen-specific antibodies during the late phase of infection. The numbers of follicular helper T cells and germinal centre B cells in γδ T-cell-deficient mice were lower than in wild-type mice during the late phase of infection. Expression profiling of humoral immunity-related cytokines in γδ T cells showed that interleukin-21 (IL-21) and interferon-γ (IFN-γ) are increased during the early stage of infection. Furthermore, blockade of IL-21 and IFN-γ signalling during the early stage of infection led to reduction in follicular helper T cells and germinal centre B cells. γδ T-cell production of IL-21 and IFN-γ is crucial for the development and maintenance of follicular helper T cells and germinal centre B cells during the late phase of infection. Our data suggest that γδ T cells modulate humoral immunity against Plasmodium infection.