In CD138-transfected Jurkat T cells and CD138-positive myeloma cells, APRIL, but not BAFF, has been shown to specifically bind heparin chain of membrane-bound CD138, but, to our knowledge, the binding of APRIL or BAFF to soluble CD138 has not been reported (35, 36). The gene discussed is TNFSF13; the disease is plasma cell myeloma.