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Published on: November 3, 2018
Phenotypic difference of normal plasma cells from mature myeloma cells
H Harada1, M M Kawano, N Huang
1Department of Internal Medicine, Hiroshima University, Japan.
Insights
Phenotypic analysis using CD19 and CD56 antibodies can distinguish normal plasma cells from myeloma cells. This method aids in detecting malignant plasma cells, even in early stages like monoclonal gammopathy of undetermined significance (MGUS).
Area of Science:
- Immunology
- Hematology
- Oncology
Background:
- Myeloma cells (plasma cells) are distinguishable from other hematopoietic cells using CD38 antibody.
- Further phenotypic characterization is needed to differentiate normal plasma cells from mature myeloma cells.
Purpose of the Study:
- To phenotypically distinguish normal plasma cells from mature myeloma cells using flow cytometry.
- To investigate the expression of CD19 and CD56 on plasma cells in monoclonal gammopathy of undetermined significance (MGUS).
Main Methods:
- Two-color flow cytometry was employed.
- Antibodies used included fluorescein isothiocyanate (FITC)-anti-CD38 and phycoerythrin-conjugated antibodies against VLA-4, MPC-1, CD44, CD56, CD19, CD20, CD24, or CD10.
- Immunophenotypes of normal plasma cells and myeloma cells were analyzed.
Main Results:
- Normal plasma cells consistently expressed CD19 and lacked CD56 (CD19+CD56-).
- Mature myeloma cells were predominantly CD19- and often CD56+ (CD19-CD56+).
- Monoclonal gammopathy of undetermined significance (MGUS) samples showed a mix of CD19+CD56- and CD19-CD56+ plasma cells.
Conclusions:
- CD19 and CD56 expression can reliably differentiate normal plasma cells from malignant myeloma cells.
- This phenotypic analysis can detect malignant plasma cells in pre-myeloma conditions like MGUS.
Abstract:
We have recently shown that two-color analysis with fluorescein isothiocyanate (FITC)-anti-CD38 antibody could clearly distinguish myeloma cells (plasma cells) from other hematopoietic cells in the bone marrow. Myeloma cells (plasma cells) alone were located at CD38strong positive (++) fractions. To further distinguish normal plasma cells from mature myeloma cells phenotypically, we examined immunophenotypes of normal plasma cells and myeloma cells by two-color flow cytometry with FITC-anti-CD38 antibody and phycoerythrin staining with antibody to VLA-4, MPC-1, CD44, CD56, CD19, CD20, CD24, or CD10. Normal plasma cells were all VLA-4+VLA-5+MPC-1+CD44+ CD19+CD56- in the bone marrows from seven healthy donors, tonsils from four patients with chronic tonsillitis, a spleen from one patient with idiopathic thrombocytopenic purpura, and lymph nodes from two patients with chronic lymphadenitis, respectively. On the other hand, mature myeloma cells (12 of 20 cases), VLA-4+VLA-5+MPC-1+, were all CD19- and most of them CD56+, and there were no myeloma cells with the CD19+CD56- phenotype in the 20 cases of myelomas we tested. Thus, as for the expression of CD19 and CD56, normal plasma cells from various tissues are all CD19+CD56-, whereas no myeloma cells have the CD19+CD56- phenotype. According to this finding, we investigated the expression of CD19 and CD56 on plasma cells (CD38++ fractions) in monoclonal gammopathy of undetermined significance (MGUS). Both CD19+CD56- and CD19-DC56+ plasma cells were found in all five cases of MGUS we tested, suggesting that MGUS consists of phenotypically normal plasma cells and myeloma cells. Therefore, it is reasoned that phenotypic analysis of plasma cells with anti-CD19 and anti-CD56 antibodies can distinguish normal plasma cells from malignant plasma cells (myeloma cells), and can detect malignant plasma cells even in MGUS or premyeloma states.
