Phenotyping studies of clonotypic B lymphocytes from patients with multiple myeloma by flow cytometry

Abstract Context.—Clonotypic B lymphocytes, monoclonal B lymphocytes sharing identical, rearranged IGH-CDR3 sequences with the patient's myeloma cells, have been detected in the peripheral blood of patients with multiple myeloma. These cells have been postulated to act as a therapy-resistant tumor reservoir that drives recurrence. Objective.—To characterize clonotypic B lymphocytes for future investigation of their role in myeloma pathogenesis. Design.—Harvests of cryopreserved peripheral blood stem-cells from 20 myeloma patients were enriched for clonotypic B lymphocytes. Cytoplasmic immunoglobulin light chain and surface immunophenotype were analyzed by flow cytometry. IGH-CDR3 gene-rearrangement pattern was performed to determine clonality. Posttransplant remission rate was compared with the percentage of clonotypic B lymphocytes. Results.—Clonotypic B lymphocytes expressing CD34±, CD38+, CD184+, CD31±, CD50±, CD138−, CD19−, CD20−, and the same immunoglobulin light chain as the patients' known myeloma ...