Chemical and immunological characterization of the electrophoretic components of the Fc fragment of human immunoglobulin G

Abstract

The major electrophoretic components of Fc prepared by plasmin digestion of human IgG ( γ 1 subclass) have been isolated and their physical, chemical and biological properties examined. The individual components showed the same amino acid composition, the same amino terminal residue, threonine, and were shown to have the same sedimentation coefficient and molecular weight by ultracentrifugal analysis. Differences in the hexose and sialic acid content of the individual components were shown not to be basis of the heterogeneity. Determination of amide nitrogen by two independent methods revealed differences which could account for the differences in mobility of the Fc components. No differences were found in the ability of the individual components to fix complement or to participate in cutaneous anaphylaxis in guinea pigs.