Follicular dendritic cells and T cells: nurses and executioners in the germinal centre reaction.

The humoral immune response constitutes an efficient system to protect the organism against diseases caused by invading pathogens. To guarantee a highly efficient defence, the humoral immune system has to be tightly regulated. Two cell subsets in particular, T cells and follicular dendritic cells (FDCs), contribute to the success of these regulation processes. Whereas the particular role of T cells is the elimination of autoreactive clones, the main role of FDCs is to present unprocessed antigen and check B-cell clones for higher affinity. B-cell clones unsuited for improved humoral immune response will be specifically killed. Involvement of Fas-mediated apoptosis might be an additional tool not only in T-cell-mediated regulation, but also in FDC-B cell interaction in the germinal centre.