The human natural anti-Gal IgG. III. The subtlety of immune tolerance in man as demonstrated by crossreactivity between natural anti-Gal and anti-B antibodies.
A well-defined antigen/antibody system was used to evaluate the effect of immune tolerance on the spectrum of specificities of natural antibodies. The antibody used in this study, anti-Gal, is a naturally occurring, polyclonal IgG that constitutes 1% of the circulating IgG in humans. We have previously shown that anti-Gal, purified from AB sera, specifically interacts with glycosphingolipids bearing a Gal alpha 1----3Gal epitope, but not with the closely related B antigen in which the penultimate galactose of the Gal alpha 1----3Gal epitope is fucosylated Gal alpha 1----3(Fuc alpha 1----2)Gal. This narrow specificity was assumed to be the result of an effective immune tolerance mechanism that prevents the expression of antibody clones that can recognize both the Gal alpha 1----3Gal and the self B epitopes. If the assumption that immune tolerance determines the range of anti-Gal specificity is correct, then anti-Gal from individuals lacking the B antigen (A and O blood types) would be expected to interact with both Gal alpha 1----3Gal and Gal alpha 1----3(Fuc alpha 1----2)Gal epitopes. In this study, anti-Gal from the serum of individuals of various blood types was purified by affinity chromatography on Gal alpha 1----3Gal adsorbent and tested for its reaction with the B antigen. Whereas anti-Gal from AB and B individuals only reacted with Gal alpha 1----3Gal epitopes, anti-Gal from A and O individuals reacted with both Gal alpha 1----3Gal and B epitopes. Furthermore, it was determined that the majority of anti-B reactivity in A and O individuals is in fact anti-Gal antibodies capable of recognizing both Gal alpha 1----3Gal and B epitopes. It can be concluded from these results that immune tolerance accurately controls the spectrum of natural antibody specificities by preventing the production of antibody clones that can interact with self antigens.
D000017:ABO Blood-Group System / Q000276:immunology*; D000906:Antibodies / Q000276:immunology / Q000302:isolation & purification; D000918:Antibody Specificity; D002846:Chromatography, Affinity; D000939:Epitopes / Q000276:immunology; D005690:Galactose / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance; D007074:Immunoglobulin G / Q000276:immunology* / Q000302:isolation & purification; D007163:Immunosorbent Techniques
D000017:ABO Blood-Group System; D000906:Antibodies; D000939:Epitopes; D007074:Immunoglobulin G; D005690:Galactose