Antigenic Relationships between Immune Globulins and Certain Related Paraproteins in Man

The antigenic properties of normal 19S gamma-globulin, pathologic macroglobulins, beta(2A)-myeloma proteins, and Bence Jones proteins have been compared with 7S gamma-globulin and the small 3.5S units derived from it by gel diffusion precipitin techniques. These studies demonstrate that the determinant groups on the 7S gamma-globulin molecule responsible for the cross-reaction with each of the other proteins are associated with the two fragments of 7S gamma-globulin which have the antibody-combining sites. The antigenic specificity of the 7S gamma-globulin which distinguishes it from each of these proteins is associated primarily with the fragment that is richest in hexose and can not combine with antigen. However when compared with certain of the paraproteins additional antigenic specificity was also found to reside in the fragments with antibody-combining activity. The finding of similar antigenic relationships in rabbit gamma-globulins suggests that some of the biological properties associated only with the 7S gamma-globulins and not with the other immune globulins may reside in the fragment which also carries the antigenic specificity of the protein.