Terminal B cell development as seen in different human myelomas and related disorders.

Immunological surface marker analysis of the mature lymphoid and plasma cells of a range of human lymphoproliferative diseases is used to show that the surface immunoglobulin (sIg) phenotype of plasma cells depends upon the isotype being secreted. Using a sensitive rosette assay, the plasma cells of all IgG (eight), IgA (six) and IgE (one) myelomas studied and of one of two cases of IgD myeloma were negative for all classes of sIg. The plasma cells from the other case of IgD myeloma expressed only sIgD, while a proportion of plasma cells from two cases of IgM myeloma and one of BJ myeloma had both sIgM and sIgD at the cell surface. The mature lymphoid and plasma cells from the two patients with mixed lymphoid/plasmacytoid proliferations of IgA type (2) carried sIgA alone, while the mature bone marrow cells from a case of Waldenström's macroglobulinaemia had only sIgM. In all the various types of immunoproliferative disease studied, a greater proportion of lymphoid cells than plasma cells possessed γFc receptors, and plasma cells were negative for receptors for EAC and μFc, and lacked the Ia-like p29, 34 antigen. These results are used to provide a scheme illustrating the terminal stages of B cell development. Examination of the peripheral blood from nineteen cases without morphological evidence of blood involvement demonstrated a monoclonal B cell proliferation in 40% of these cases. Immunological analysis of lymphocyte subpopulations showed that both E-rosette-forming cells and sIgM and sIgD normal B cells were depressed in most cases and that there was a corresponding increase in FcsIg and/or null (FcsIg) cells.