Tumor necrosis factor receptor superfamily, member 13C (TNFRSF13C) also known as B-cell-activating factor receptor (BAFFR) and CD268 antigen, is a member of the tumor necrosis factor receptor superfamily. BAFF promotes the survival of B cells and is essential for B cell maturation. BAFF binds to three TNF receptor superfamily members: B-cell maturation antigen (BCMA/TNFRSF17), transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI/TNFRSF13B) and BAFF receptor (BAFF R/BR3/TNFRSF13C). These receptors are type III transmembrane proteins that lack a signal peptide. BAFF R is highly expressed in spleen, lymph node and resting B cells. It is also expressed at lower levels in activated B cell, in resting CD4+ T cells, in thymus and peripheral blood leukocytes. BAFF knockout mice lack mature B cells. Similarly, A/WySnJ mice that are defective in BAFF-R intracellular signaling also lack mature B cells, suggesting that BAFF R is the critical receptor for BAFF during B lymphopoiesis. It has been proposed that abnormally high levels of BAFFR/TNFRSF13C (CD268) may contribute to the pathogenesis of autoimmune diseases by enhancing the survival of autoreactive B cells.