In multiple myeloma clonotypic CD38- /CD19+ / CD27+ memory B cells recirculate through bone marrow, peripheral blood...

It is believed that myeloma cells are derived from a germinal center (GC) or post GC B cell. The GC B cell can differentiate into both a memory B cell and a plasma cell (PC). In this study, we investigated the recirculating potential of memory B cells clonally related to the myeloma PC (termed clonotypic). The V(H)DJ(H) immunoglobulin gene rearrangement of the myeloma clone was identified for 10 myeloma patients and allele-specific oligonucleotides (ASO) IgH RT-PCR assays were designed for each patient. Memory B cells (CD38- /CD19+ /CD27+) and their subsets defined by the monoclonal antibodies CD62L, CCR6, CXCR4, CXCR5, CCR7 were flow-sorted as single cells and analyzed by ASO RT-PCR analysis. In addition, aspirated peripheral lymph nodes (PLN) of 7 myeloma patients in complete or partial remission were analyzed for the presence of clonotypic cells. Circulating clonotypic memory B cells were identified in PBMNC of 7/10 patients and both CD62L positive and negative clonotypic memory B cells were identified. Furthermore, comparable frequencies of clonotypic cells were found in the CCR6 +/- and CXCR4 +/- memory B cell subsets, whereas all clonotypic memory and later stage B cells were CXCR5 positive. In accordance with their immunophenotype, clonotypic memory B-cells were identified in peripheral blood, bone marrow and PLNs. Clonotypic memory B-cells were present in the majority of myeloma patients and seem to have the same diverse recirculating/homing capacity as normal memory B cells.