Germinal center formation in mice lacking alpha beta T cells

T cells are essential for inducing clonal B cell expansion in germinal centers during T cell-dependent antibody responses. However, class-switched antibodies are readily detectable in TCR alpha-deficient mice that congenitally lack crp T cells, including those such as IgG1 that are considered to be dependent on collaboration between B cells and alpha beta T cells. This observation suggests that a novel form of B:T collaboration may be evident in TCR alpha(-/-) mice. We report that germinal centers develop spontaneously in mice lacking T cell receptor ct genes (TCR alpha(-/-)), despite the absence of alpha beta T cells. They are not seen in TCRB(-/-) mice kept in similar conditions. Both strains of mice have gamma delta T cells, but it is a subset of T cells expressing TCR beta and CD4 that is dominant in the germinal centers of TCR alpha(-/-) mice. Exceptionally, germinal centers were associated with CD4(+) gamma delta T cells. The expression of CD4 seems to be important, for few extrafollicular T cells have CD4 and CD4 is largely absent from TCR beta(-/-) T cells. The CD4(+) TCR beta cells may help B cells produce autoantibodies that have been identified in TCR alpha(-/-) mice.