Cutting edge: Germinal centers can be induced in the absence of T cells

Immunization of mice containing mutations that inactivate the TCR C beta an d C delta genes with the T cell-independent (TI) type 2 Ag (4-hydroxy-3-nit rophenyl)acetyl-Ficoll induces clusters of peanut agglutinin-binding B cell s in the spleen. These clusters are histologically indistinguishable from g erminal centers (GCs) typical of T cell-dependent immune responses. They ar e located in follicles, and contain mature follicular dendritic cells, immu ne complex deposits, and B cells that display the phenotypic qualities of c onventional GC B cells. However, the kinetics of this TI GC response differ from T cell-dependent GC responses in being rapidly induced and of short d uration. Moreover, the Ab V genes expressed in TI GCs have not undergone so matic hypermutation. Therefore, T cells may be required for B cell differen tiation processes associated with the intermediate and latter stages of the GC reaction, but they are dispensable for the induction and initial develo pment of this response.