One percent of human circulating B lymphocytes are capable of producing the natural anti-Gal antibody.
The natural anti-Gal antibody constitutes 1% of circulating IgG in humans and interacts specifically with the carbohydrate epitope Gal alpha 1-3Gal beta 1-4GlcNAc-R (the alpha-galactosyl epitope). In view of the unusually large amounts of this antibody in the serum, it was of interest to determine the proportion of circulating B lymphocytes capable of synthesizing anti-Gal. For this purpose, blood B lymphocytes were incubated with Epstein-Barr virus (EBV) and plated in microtiter wells. Proliferation of the EBV transformed B lymphocytes was readily visible after 3 weeks of incubation. The supernatants from wells containing proliferating B-lymphoid clones were assayed for anti-Gal by an agglutination assay with rabbit red blood cells and the specificity of the agglutinating antibodies was further confirmed by their interaction with synthetic oligosaccharides and by enzyme-linked immunosorbent assay with glycoproteins. Approximately 5% of the wells contained anti-Gal antibodies. Limiting dilution studies and IgH gene rearrangement patterns suggested that each well contained an average of five proliferating B-lymphoid clones. Thus, it is concluded that approximately 1% of circulating B lymphocytes are capable of producing anti-Gal. The proportion of anti-Gal--producing lymphoid clones exceeds by fourfold that of clones producing anti-blood group A or anti-blood group B antibodies. Individual anti-Gal clones display fine variations in their combining site, as indicated by their differential interaction with alpha-galactosyl epitopes on glycolipids and on N-linked carbohydrate chains of glycoproteins. The high frequency of precursor B lymphocytes capable of producing anti-Gal, found in every individual and the restricted specificity of this antibody to alpha-galactosyl epitopes, potentially makes anti-Gal--producing lymphocytes an effective system for studying human Ig genes involved in the natural immune response to structurally defined haptens.
Galili
U
U
Department of Microbiology and Immunology, Medical College of Pennsylvania, Philadelphia 19129.
Anaraki
F
F
Thall
A
A
Hill-Black
C
C
Radic
M
M
D000017:ABO Blood-Group System / Q000276:immunology; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002461:Cell Line, Transformed; D002999:Clone Cells; D000939:Epitopes; D005690:Galactose / Q000276:immunology*; D005803:Genes, Immunoglobulin; D004854:Herpesvirus 4, Human; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis*; D007132:Immunoglobulin Isotypes / Q000032:analysis
D000017:ABO Blood-Group System; D000939:Epitopes; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D005690:Galactose