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-sw itched antibodies are readily detectable in TCR alpha-deficient mice t hat congenitally lack crp T cells, including those such as IgG1 that a re considered to be dependent on collaboration between B cells and alp ha beta T cells. This observation suggests that a novel form of B:T co llaboration may be evident in TCR alpha(-/-) mice. We report that germ inal centers develop spontaneously in mice lacking T cell receptor ct genes (TCR alpha(-/-)), despite the absence of alpha beta T cells. The y are not seen in TCRB(-/-) mice kept in similar conditions. Both stra ins of mice have gamma delta T cells, but it is a subset of T cells ex pressing TCR beta and CD4 that is dominant in the germinal centers of TCR alpha(-/-) mice. Exceptionally, germinal centers were associated w ith CD4(+) gamma delta T cells. The expression of CD4 seems to be impo rtant, for few extrafollicular T cells have CD4 and CD4 is largely abs ent from TCR beta(-/-) T cells. The CD4(+) TCR beta cells may help B c ells produce autoantibodies that have been identified in TCR alpha(-/- ) mice.