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DAP-related apoptotic kinase-2 (DRAK2), a death-associated protein kinase family member, is highly expressed in B and T lymphocytes in the human and the mouse. To determine whether DRAK2 plays a role in B-cell activation and differentiation, we analyzed germinal centers (GCs) and the specific antibody response to NP in drak2^{− / −} mice immunized with the thymus-dependent (TD) conjugated hapten NP₁₆-CGG. In drak2^{− / −} mice, spleen GCs were normal in size and morphology, but their number was reduced by as much as 5-fold, as compared to their wild-type littermates. This was not due to a defect in B-cell proliferation, as the BrdU uptake was comparable in DRAK2-deficient and wild-type B cells. Rather, the proportion of apoptotic GC B and T cells in drak2^{− / −} mice was significantly higher than that in wild-type control mice, as shown by 7-AAD and terminal deoxynucleotide transferase dUTP nick end …