TNFSF13B and autoimmune thrombocytopenic purpura: Autoreactive antibodies are secreted by plasma cells, which have been reported to be present at higher levels in patients with ITP [72], as well as the B cell regulator, and B cell-activating factor (BAFF, also called B cell stimulator (BlyS)), which is an important factor in B cell selection, survival, and proliferation.