Six color flow cytometry detects plasma cells expressing aberrant immunophenotype in bone marrow of healthy donors

BACKGROUND: Both normal and malignant plasma cell (PC) populations can be identified using modern flow cytometry (FC) technique in multiple myeloma (MM) patients. Expression of CD19 and CD56 markers is heterogenous on bone marrow PCs of healthy individuals. Little is known about immunophenotypically aberrant (CD19-/CD56+) PCs subpopulation of healthy people. METHODS: Using six color FC, we analyzed PCs in BM samples of 11 healthy donors (HD) and compared their immunophenotypic properties with clonal PC populations from MM patients. RESULTS: Both immunophenotypically normal (CD19+/CD56-) and aberrant (CD19-/CD56+) PC populations could be detected in 10 of 11 HDs' BM samples and constituted the median of 60.3% (37.3-72.3) and 9.6% (0-35.7) of BM PCs, respectively. CD19, CD56, CD38, CD45, and CD20 marker expression characteristics were of little value discriminating clonal PCs of MM patients from immunophenotypically aberrant PCs of healthy donors. CONCLUSIONS: Our findings suggest that aberrant immunophenotype is common in BM PCs of healthy people. Improvements in FC methodology to separate normal and malignant PCs remain an open area for future investigations.