Among B cell-stimulating cytokines, higher levels of serum BAFF (44), and higher frequency of circulating B cells expressing BAFF receptor (BAFF-R), have been reported in MG patients, in both AChR- and MuSK-MG (45, 46), indicating abnormal B cell survival. The gene discussed is TNFRSF13C; the disease is myasthenia gravis.