Myeloma clonotypic B cells are hampered in their ability to undergo B-cell differentiation in vitro.
In the peripheral blood (PB) of multiple myeloma (MM) patients, clonotypic B cells are present that express the identical V(D)J rearrangements as the malignant plasma cells in the bone marrow. In the present study, the proliferative capacity of clonotypic B cells from MM patients (n = 10) and the ability to differentiate in vitro was determined using the CD40-culturing system. For six patients, the presence of clonotypic B cells expressing variant immunoglobulin (Ig) isotypes was assessed by Ig isotype-specific allele-specific oligonucleotide reverse transcription polymerase chain reaction (ASO-RT-PCR) after culturing with CD40L and interleukin 4 (IL-4). In three out of six patients, clonotypic B cells expressing variant isotypes were detected both before and after culturing. The ability of clonotypic B cells to undergo B-cell differentiation was studied by abrogating CD40 signalling accompanied by IL-10 and IL-2 stimulation, enhancing differentiation towards Ig-secreting cells. The numbers of clonotypic B cells were determined by quantitative ASO-PCR. An increase in cell number was observed upon CD40L and IL-4 stimulation, whereas the relative number of clonotypic B cells was unaltered. In contrast, upon B-cell differentiation the relative number of clonotypic B cells decreased. In conclusion, clonotypic B cells can be cultured and isolated in vitro using the CD40 system. Clonotypic B cells responded to CD40 triggering in a similar fashion as to non-clonotypic normal B cells. However, the ability of clonotypic B cells to undergo in vitro activation and differentiation into Ig-secreting cells is hampered.
D001402:B-Lymphocytes / Q000473:pathology*; D015139:Blotting, Southern; D019013:CD40 Antigens; D023201:CD40 Ligand / Q000494:pharmacology; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000032:analysis; D015847:Interleukin-4 / Q000494:pharmacology; D009101:Multiple Myeloma / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D019013:CD40 Antigens; D007132:Immunoglobulin Isotypes; D023201:CD40 Ligand; D015847:Interleukin-4