The role of Ag-Ab complexes (or immune complexes; ICs) in the regulation of the maturation of the B cell immune response was investigated in mice perturbed in the deposition and retention of such complexes. Loss of surface expression of Fc gammaRI and Fc gammaRIII due to targeted disruption of the common FcR gamma-chain gene results in dramatically increased deposition of ICs on follicular dendritic cells (FDCs) in germinal centers (GCs), attributed to altered clearance of circulating ICs. Despite these changes in the trapping of ICs by FDCs, serum Ab production, V gene hypermutation, isotype class switching and Ab affinity maturation are overtly unaltered. Thus, substantially augmenting B cell cognate Ag density on FDCs does not alter the outcome of the maturation of the B cell response. The significance of this finding in terms of the currently accepted model for the generation of B cell memory is discussed.