Differing surface marker characteristics in plasma cell dyscrasias with particular reference to IgM myeloma.

Immunological marker studies using direct immunofluorescence and rosette methods were performed on the bone marrow and peripheral blood of an IgM myeloma, and on the peripheral blood of two cases of IgA myeloma and one IgG myeloma. These studies confirmed the peripheral blood involvement in plasma cell dyscrasias. In the IgA myeloma, the membrane and cytoplasmic immunoglobulin was restricted to IgA, and the IgG myeloma did not express immunoglobulin at the surface of the cells shown to contain cytoplasmic IgG. The IgM myeloma cells, on the other hand, expressed membrane immunoglobulin, including IgD, of a single light chain type. The majority of plasma cells secreting IgA or IgG did not express the IgG Fc receptor, but most of the cells from the IgM myeloma, including plasma cells, did express IgG Fc receptors.