EXPRESSION OF THE HEMATOPOIETIC STEM-CELL ANTIGEN CD34 ON BLOOD AND BONE-MARROW MONOCLONAL PLASMA-CELLS FROM PATIENTS WITH MULTIPLE-MYELOMA

Monoclonal plasma cells (CD38(+)CD45(-)/dim) are typically present in the blood of patients with active myeloma and can contaminate stem cel l harvests. This has led to strategies that select CD34(+) cells for u se in autologous stem cell transplantation with the goal of decreasing tumor cell contamination, The aim of this study was to learn if the C D34 antigen is expressed on monoclonal plasma cells in the blood or ma rrow of patients with multiple myeloma. We used three-color flow cytom etry (surface CD38;CD45 and cytoplasmic kappa or lambda) to identify m onoclonal plasma cells in the blood (n = 24) and marrow (n = 37) from patients with plasma cell proliferative disorders, In each case the CD 38(+)CD45(-) and CD38(+)CD45(dim+) monoclonal populations were then an alyzed for CD34 expression. In all 24 blood and 37 marrow samples, the CD38(+)CD45(-) monoclonal plasma cells were negative for CD34 express ion. CD38(+)CD45(dim+) monoclonal cells were documented in the blood o f 11 patients and in the marrow of 33 patients and this cell populatio n was also CD34-negative in all cases, These results indicate that CD3 4 is usually not expressed on the CD38(+)CD45(-)CD45(dim+) monoclonal plasma cells in the blood or marrow of patients with plasma cell proli ferative disorders. CD34 selection methods should therefore decrease t he chance of tumor cell contamination of the stem cell product.