Immunological phenotype of neoplasms involving the B cell in the last step of differentiation

Abstract

Summary. The immunological phenotype of diseases involving the last step of B cell differentiation—multiple myeloma (MM, 38 patients) and Waldenström's macroglobulinaemia (WM, 12 patients)—was analysed with a panel of monoclonal antibodies (McAb) as well as conventional markers. Most of the bone marrow plasma cells (80%) from MM patients reacted with the McAb OKT10, FMC8 and FMC48. Plasma cells were consistently negative with FMC7, Leu-1 and mouse rosettes. Ia, B1 and SIg were expressed in a minority of plasma cells (+ phenotype. Mouse rosettes and Leu-1 were positive in one case; OKT10 was positive in three out of five WM patients studied. This phenotype indicates that WM cells correspond to an earlier stage of B cell differentiation than MM plasma cells. The McAb J5 was positive in three out of six MM and two out of four WM analysed. The antigenic differences observed in MM and WM patients support the notion that the cells of the neoplastic clone are able to undergo a certain degree of differentiation.