Human myeloma cells express the CD38 ligand CD31.

Multiple myeloma (MM) plasma cells (PC) are CD38+. A ligand for CD38 is the adhesion molecule CD31. By flow cytometry and immunocytochemistry we have investigated whether malignant PC co-express CD38 and CD31. All 68 patients studied were CD38+. 14/14 monoclonal gammopathies of undetermined significance (MGUS) and 39/39 plasmacytic MM patients co-expressed CD38 and CD31 at high density. Only 1/11 plasmablastic MM and 1/4 plasma cell leukaemias (PCL) expressed CD31. These data indicated that PC malignancies co-expressed high levels of both CD38 and its ligand CD31, with the exception of plasmablastic MM and PCL.