Objective: To describe the immunophenotype of normal and myelomatous plasma cells (PCs) and the changes in immunoregulatory nonmyelomatous cells in multiple myeloma (MM).
Design: The cell surface markers (antigens) associated with this common cancer were reviewed.
Material and methods: Immunophenotypic characterization of both normal PCs and their counterpart malignant hematopoietic cells can be achieved by using monoclonal antibodies and either flow cytometry or immunocytochemical techniques.
Results: Normal PCs are heterogeneous and express, in addition to cytoplasmic immunoglobulins, the antigens CD9, CD10, CD13, CD19, CD20, CD33, CD38, and D-related human leukocyte antigen (HLA-DR). This heterogeneity also occurs in malignant PCs. Myelomatous PCs may express, in addition to CD38 (the most typical PC marker), the antigens CD9, CD10, HLA-DR, and CD20. Other non-B-cell lineage markers such as myeloid (CD13, CD14, CD15, CD33, CD41, and glycophorin A), T-cell (CD2 and CD4), and natural killer-associated (CD56) antigens, as well as CD23, CD24, CD25, CD37, CD39, CDw40, CD45R, CD71, and certain unclustered antigens (R1-3, PCA-1, PCA-2, PC1, 62B1, 8A, 8F6, and MM4), have been noted in myelomatous PCs. The presence of these antigens in the myeloma cells may have a prognostic value--for example, the expression of CD20 and of myelomonocytic antigens (CD11b, CD13, CD14, CD15, and CD33) may be related to a poor prognosis. The adverse prognostic implication of the expression of CD10 initially described in MM has not been subsequently confirmed. Patients with MM may have mononuclear cells in their peripheral blood that express the same antigens as those expressed by the myeloma cells in their bone marrow. The presence of such cells or their therapy-associated decrease or disappearance may be related to the prognosis of patients with MM.
Conclusion: The presence of cell surface markers on PCs and their prognostic significance in patients with MM warrant further investigation.