Serologic cross-reactions among rabbit secretory IgA molecules: evidence for multiple subclasses of secretory IgA-f molecules.
Serologic cross-reactions among allotypes of rabbit secretory IgA (sIgA) of the f-subclass were examined by quantitative radiobinding assays with various allo-anti-alpha chain reagents. Numerous cross-reactions were observed which demonstrated the complexity of the C alpha f allotypes. One of the reagents used in these studies reacted not only with all sIgA molecules of the immunogen C alpha f allotype but also with all sIgA molecules of the other C alpha f allotypes. Aliquots of the antiserum were each adsorbed with IgA molecules of these C alpha f allotypes and then used in radiobinding studies with sIgA-f molecules of the various C alpha f allotypes. The adsorbed reagents reacted with some but not all sIgA-f molecules, thus indicating that the C alpha f allotypes each comprise more than one serologically distinguishable subset. Results from these radiobinding experiments were used to develop a model in which each of the five IgA-f allotypes comprises at least two serologically distinguishable subsets. Each of these subsets expresses a unique pattern of C alpha determinants. These C alpha determinants appear to be protein in nature rather than carbohydrate as periodate oxidation of the sIgA-f glycoproteins does not affect the reactions of the molecules with the cross-reactive alloreagents. IgA molecules of the serologically distinguishable subsets presumably differ in amino acid sequence in the constant region and, thus, would be products of distinct C alpha genes. Therefore, it is probable that the cross-reactions of these molecules, which were previously thought to comprise a single subclass, sIgA-f, may reflect the presence of more than one subclass of sIgA-f molecules, i.e., a third subclass of rabbit sIgA.
D000818:Animals; D003429:Cross Reactions; D000939:Epitopes; D007071:Immunoglobulin A, Secretory / Q000145:classification / Q000276:immunology*; D007126:Immunoglobulin Allotypes; D007518:Isoantibodies / Q000276:immunology; D007519:Isoantigens / Q000276:immunology; D010084:Oxidation-Reduction; D010504:Periodic Acid; D011817:Rabbits; D011869:Radioligand Assay
D000939:Epitopes; D007071:Immunoglobulin A, Secretory; D007126:Immunoglobulin Allotypes; D007518:Isoantibodies; D007519:Isoantigens; D010504:Periodic Acid