Molecular Heterogeneity of Immunoglobulin-M (γM-Globulin)

Abstract

Summary: Low-molecular weight 7 S protein with γM antigenic determinants (LMW-γM) has been identified in normal human serum and in sera obtained from patients with a variety of disease states. In particular, LMW-γM protein was detected in approximately 50% of patients with lymphoproliferative disorders who had 19 S-macroglobulinemia (HMW-γM). Several types of techniques were employed to separate and distinguish these two molecular forms of γM protein found in fresh serum. These included sucrose density ultracentrifugation, gel filtration and immuno-gel filtration. This protein could also be detected directly in serum, and its level determined by immunodiffusion in 7% agarose gels. A third type of protein with γM antigenic determinants was also detected in certain sera. This γM component, which sedimented more slowly than LMW-γM and was antigenically deficient when compared with both LMW-γM and HMW-γM or with the monomeric subunit of HMW-γM appeared to result from proteolytic cleavage of HMW-γM protein.