Human anti-Gal heavy chain genes. Preferential use of VH3 and the presence of somatic mutations.
Anti-Gal is the most abundant natural Ab known in humans. It interacts specifically with the carbohydrate structure Gal alpha 1-3 Gal beta 1-4GlcNAc-R (termed the alpha-galactosyl epitope), constitutes approximately 1% of circulating Ig, and is found in all three isotypes in the serum. Anti-Gal is produced in Old World monkeys, apes, and humans, and in no other mammalian species. The objective of this study was to determine the VH genes involved in the synthesis of anti-Gal. B lymphocytes from various individuals were transformed by EBV, the clones producing anti-Gal were isolated, the specificity and affinity of the Abs were determined, and the VH genes were sequenced. The affinity of anti-Gal clones for the free radiolabeled alpha-galactosyl epitope ranged between 1.1 x 10(6) M-1 and 5 x 10(8) M-1. Eight of the nine clones studied used VH3 family genes and one clone used a VH1 family gene. Four of the five VH3 genes used were found to form a cluster of related sequences, suggesting that functional constraints may lead to the use of VH3 genes with structural motifs that are suited for specific interactions with the alpha-galactosyl epitope. Comparison with known germline sequences for all of the clones studied and analysis of autologous germ-line genes in two of the clones indicate that anti-Gal VH genes undergo somatic mutations. These somatic mutations may provide a pool of variants that are available for affinity maturation.
Wang
L
L
Department of Microbiology and Immunology, Medical College of Pennsylvania, Philadelphia 19129, USA.
Radic
M Z
MZ
Galili
U
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D000595:Amino Acid Sequence; D000818:Animals; D000910:Antibodies, Heterophile / Q000235:genetics*; D000911:Antibodies, Monoclonal / Q000235:genetics; D001483:Base Sequence; D002240:Carbohydrate Sequence; D002461:Cell Line, Transformed; D000939:Epitopes / Q000276:immunology; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005803:Genes, Immunoglobulin; D006801:Humans; D007113:Immunity, Innate; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D011323:Primates / Q000276:immunology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D000910:Antibodies, Heterophile; D000911:Antibodies, Monoclonal; D000939:Epitopes; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region