STUDIES ON HUMAN ANTIBODIES V. Aml~O ACID Co~osrrloI~ oF ANTIDEXTI~AI~S OF Trim S~m~ AND OF DZF]?ERING SPECI-~ICITIES FROM SEVERAL INDIVIDUALS* BY MARIANNE M. DORNER, M.D., EMMETT W. BASSETT, PH.D.,

Recent investigations (1) have revealed striking differences in the amino acid composition of four different human 3'G--antibodies from one individual. These antibodies, antilevan, antidextran, antiteichoic acid, and anti-blood group A substance, included an antidextran of a-(1 ~ 6) specificity. In the present study, amino acid analyses were carried out on three additional human antidextrans of a-(1 ~ 6) specificity as washed dextran-antidextran-specific precipitates. In addition, antibody fractions were analyzed from three individuals who had been immunized with a dextran containing two types of antigenic determinants and who had formed some antibodies directed against a-(1 ~ 6)linked glucosyl units and others specific for a-(1 --o 2)-linked glucose residues (2). After precipitation of the antidextran of or-(1 ~ 6) specificity with a dextran containing 96% of or-(1 ~ 6) and 4% of a-(1 --o 3) linkages, the remaining antibody was precipitated from the supernatant fluids with the homologous dextran. Comparison of the amino acid composition of the various antidextrans of a-(1 ~ 6) specificity showed wide variations in cer tain amino acids. Significant differences were also observed in the antidextran fractions from a given individual produced against the two types of antigenic determinants. The extensive variations found provide further indications of the vast heterogeneity (3) of human antibodies even to well defined antigenic determinants of simple structure.