To describe the immunophenotype of normal and myelomatous plasma cells (PCs) and the
changes in immunoregulatory nonmyelomatous cells in multiple myeloma (MM).
The cell surface markers (antigens) associated with this common cancer were reviewed.
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.
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.
The presence of cell surface markers on PCs and their prognostic significance in patients
with MM warrant further investigation.