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Updated: Aug 2, 2026
An Organotypic High Throughput System for Characterization of Drug Sensitivity of Primary Multiple Myeloma Cells
Published on: July 15, 2015
Plasma cells in peripheral blood stem cell harvests from patients with multiple myeloma are predominantly polyclonal
1Institute of Haematology, Royal Prince Alfred Hospital, Sydney, NSW, Australia.
Insights
A new flow cytometry method identifies plasma cells in PBSC harvests. It reveals most myeloma plasma cells are immature and polyclonal, with monoclonality best detected in mature cells.
Area of Science:
- Immunology
- Hematology
- Oncology
Background:
- Plasma cells are crucial in multiple myeloma pathogenesis.
- Assessing plasma cell clonality in peripheral blood stem cell (PBSC) harvests is vital for treatment monitoring.
- Current methods for detecting plasma cell clonality can be limited.
Purpose of the Study:
- To develop and validate a flow cytometric technique for detecting plasma cells in PBSC harvests.
- To establish light chain restriction as a reliable marker for plasma cell clonality.
- To characterize the maturity and clonality of plasma cells in PBSC harvests from myeloma patients.
Main Methods:
- Flow cytometry was used to identify plasma cells based on CD38 and cytoplasmic immunoglobulin expression.
- Light chain (kappa/lambda) restriction was assessed to determine clonality.
- Plasma cells were further categorized into immature (CD45+) and mature (CD45-) subsets.
Main Results:
- All studied PBSC harvests contained plasma cells, including those from non-myeloma patients.
- The majority of plasma cells in myeloma patient harvests were immature (CD45+).
- Light chain restriction, indicating monoclonality, was more frequently detected in mature (53%) than immature (9%) plasma cells.
Conclusions:
- Most plasma cells in PBSC harvests from myeloma patients are immature and polyclonal.
- Mature plasma cells are the primary repository for detectable monoclonality in these harvests.
- Flow cytometry with light chain restriction analysis is effective for assessing plasma cell clonality in PBSC harvests.
Abstract:
A flow cytometric technique has been developed to detect individual plasma cells in PBSC harvests and to establish light chain restriction as a surrogate marker of their clonality. Plasma cells were identified by high intensity CD38 (CD38++) and cytoplasmic immunoglobulin (cIg) expression. The ratio of cytoplasmic kappa to lambda expression was used to detect light chain restriction. All 25 PBSC harvests studied contained CD38++/cIg plasma cells (mean 0.7%, range 0.03-2%). Harvests from non-myeloma patients also contained plasma cells (mean 0.4%, range 0.01-1.5%). Most of the plasma cells detected in the harvests from myeloma patients were immature (CD45+/CD45++) rather than mature (CD45-). When the total plasma cell population was studied, definite isotype restriction could be detected in only 16% of harvests. Light chain restriction was found in 53% of harvests when the mature plasma cells (CD45-) were analysed but only in 9% of harvests when immature (CD45+/CD45++) plasma cells were analysed. Five percent of patients with myeloma had detectable light chain restriction in peripheral blood CD19+ cells. There was concordance between the ratio of malignant (CD19-/CD56+) to normal (CD19+/CD56-) plasma cells and light chain expression in 86% of patients studied. This study has demonstrated that the majority of plasma cells in PBSC harvests from patients with myeloma are not only immature but are also predominantly polyclonal and that monoclonality is best detected in mature plasma cells.
