TUMOR-SPECIFIC ANEUPLOIDY NOT DETECTED IN CD19(-LYMPHOID CELLS FROM MYELOMA PATIENTS IN A MULTIDIMENSIONAL FLOW CYTOMETRIC ANALYSIS() B)

Aneuploidy and lg light chain restriction were used as separate, indep endent turner specific markers to study 26 patients with multiple myel oma to determine whether bone marrow B cells, as defined by CD19 expre ssion, are clonally related to myeloma plasma cells. Specimens were ch aracterized using multidimensional flow cytometry to identify the pres ence of clonality in both the B lymphoid and plasma cell populations u sing both surface and cytoplasmic staining with antibodies specific fo r kappa or lambda Ig light chain. In none of the patients with multipl e myeloma were CD19(+) cells found to be clonally restricted to kappa or lambda. The monoclonal plasma cells (MPC) were found to be uniforml y negative for CD10, CD19, and CD34, while the CD19(+) B lymphoid cell s present within the samples expressed normal intensities and relation ships of these antigens, which allowed them to serve as internal posit ive controls. Combined analysis of cell surface antigen expression and DNA content allowed plasma cell populations to be characterized for a neuploidy without interference from normal bone marrow cells. The MPC, detected on the basis of bright CD38 expression (CD38(++)), demonstra ted DNA aneuploidy in 65% of cases (DNA index range of 0.9 to 1.3). Th ese aneuploid DNA distributions had typical cell cycle profiles (inclu ding G1, S, and G2 + M) expected of a proliferating population. In all cases, DNA aneuploidy was confined almost entirely to the CD38(++), C D19(-) malignant plasma cells, while cells expressing CD19 were diploi d. These results support the concept that myeloma is a disease process mediated by self-replicating, late compartments of B-cell ontogeny. ( C) 1996 by The American Society of Hematology.