A “monoclonal” type, low molecular weight protein related to γM-macroglobulins

Abstract

A unique “monoclonal” gamma globulin was detected in the serum of a patient with malignant disease of the plasma cell-lymphatic system. This protein had antigenic determinants common to 19S γM-globulin (macroglobulin) but there were marked physicochemical differences. The clinical and pathologic findings in this patient differed from those usually found in patients with multiple myeloma or Waldenström's macroglobulinemia. Evidence obtained from density gradient and gel filtration studies of whole serum indicated that the γM antigenic determinants were located primarily on molecules smaller in size than 19S-globulin. The anomalous gamma globulin, isolated from serum, had a sedimentation coefficient ( s 20, w) of 6.5S, consisted of μ-type heavy chains and λ-type light chains and differed slightly from the monomeric subunits of a reduced alkylated 19S γM-globulin. This protein may be related to low molecular weight γM antibodies previously described in a normal serum and in several disease states.