CD10-(CALLA)-Positive Lymphocytes in Myeloma: Evidence that they are a Malignant Precursor Population and are of Germinal Centre Origin

CD10 antigen has been repeatedly detected on putative lymphoid precursor populations in both the bone marrow and circulation of multiple myeloma patients, as well as on the plasma cells in some cases of myeloma. The presence of these CD10-positive cells has raised questions regarding the ontogeny of the proliferating precursor cell in myeloma. The majority opinion has implicated a CD10-positive haemopoietic progenitor cell. However, the CD10 antigen has been detected on some mature B cells, i.e. germinal centre B cells. In this paper we postulate that the proliferating precursor cell in myeloma arises from the germinal centre. The germinal centre is the site of affinity maturation of antibody responses via somatic mutation and of isotype switching. Thus the siting of the clonogenic cell in myeloma in the germinal centre explains the overwhelming predominance of IgG and IgA myelomas, the phenomenon of point mutation which occurs in myeloma proteins in the presence of stable immunoglobulin gene rearrangements and the impaired primary immune response in myeloma. It is also consistent with the requirement for antigenic exposure in the development of myelomatosis.