Human myeloma cells express the CD38 ligand CD31

Multiple myeloma (MM) plasma cells (PC) are CD38(+). A ligand for CD38 is t he adhesion molecule CD31, By flow cytometry and immunocytochemistry we hav e investigated whether malignant PC co-express CD38 and CD31. All 68 patien ts studied were CD38(+). 14/14 monoclonal gammopathies of undetermined sign ificance (MGUS) and 39/39 plasmacytic MM patients co-expressed CD38 and CD3 1 at high density, Only 1/11 plasmablastic MM and 1/4 plasma cell leukaemia s (PCL) expressed CD31. These data indicated that PC malignancies co-expres sed high levels of both CD38 and its ligand CD31, with the exception of pla smablastic MM and PCL.