Recent immunophenotypic analysis has shown that the heterogeneous expression of the adhesion molecule VLA-5 classifies myeloma cells into VLA-5+ mature and VLA-5- immature subpopulations. To further clarify the two myeloma subpopulations, we generated a monoclonal antibody, MPC- 1, by immunizing mice with an adherent human myeloma cell line, KMS-5. The MPC-1 antibody recognized a 48-Kd surface antigen on KMS-5 but not on U-266, a nonadherent human myeloma cell line. Specificity characterization showed that MPC-1 antigen was expressed on mature myeloma cells, normal plasma cells, and mature B cells, whereas pre-B cells and germinal center B cells lacked its expression. Monocytes and a human bone marrow stromal cell line, KM102, also expressed this antigen. Two subclones of MPC-1+ VLA-5+ (KMS-5Ad) and MPC-1-VLA-5+ (KMS- 5NAd) were separated from the KMS-5 cell line. The KMS-5NAd adhered to KM102 more tightly than did the KMS-5NAd, and the U-266 (MPC-1-VLA-5-) displayed almost no adherence to the KM102. The adhesion of the KMS-5Ad was partially inhibited by the MPC-1 antibody. These results, taken together, suggest that the MPC-1 antigen serves as a differentiation marker for B-lineage cells, including plasma cells, and may function as an adhesion molecule involved in the interaction of mature myeloma cells with bone marrow stromal cells.

This content is only available as a PDF.