Studies on human antibodies. VI. Selective variations in subgroup composition and genetic markers.

The composition of various isolated antibodies was determined by quantitative analyses for heavy chain subgroups and light chain types. Certain antibodies such as anti-tetanus toxoid and anti-A isoagglutinins were predominantly of the major gammaG1-type. However, a high preponderance of molecules of the minor gammaG2-subgroup was found for antibodies to dextran, levan, and teichoic acid. These findings explain some unusual features previously noted for anti-dextrans such as weak PCA reactions and lack of Gm antigens. Studies of several isolated antibodies from single heterozygous individuals showed a selective absence of genetic markers in certain antibodies and their presence in others. The "allelic exclusion" principle was clearly evident in the isolated antibodies of two different individuals. Large differences in the ratio of kappa to lambda light chains were observed for the same type of antibody from different individuals. Subfractionation of dextran antibodies by affinity for specific glycosidic linkage or combining site size produced marked changes in the ratios. The isomaltohexaose eluates of the dextran antibodies from two subjects were primarily kappa and the isomaltotriose eluates were predominantly lambda. The one anti-levan antibody studied was uniquely homogeneous, consisting exclusively of gammaG2-heavy chains and kappa light chains. By these criteria as well as others, it closely resembled myeloma proteins.