Gastric plasmacytoma: an immunologic and immunohistochemical study.

A case of IgG (lambda) secreting plasmacytoma arising in the stomach has been presented. Immunohistochemically, the tumor cells contained IgG-lambda immunoglobulin. Immunoelectrophoretic study on patient's serum revealed in the gamma zone the presence of M protein which reacted specifically with anti-IgG and anti-lambda antisera. Agar electrophoresis and immunofixation electrophoresis with anti-IgG and anti-lambda antisera showed multiple subbands. Neuraminidase treatment of the purified IgG from this patient resulted in gradual reduction of four subbands to two. Electrophoretic charge difference of the monoclonal immunoglobulin may be attributed to incompletely synthesized sugar chains attached to the protein core.