Specificity and prevalence of natural bovine anti-alpha galactosyl (Gal alpha 1-6Glc or Gal alpha 1-6Gal) antibodies

Immunity against the carbohydrate components of microorganisms mediated by antibodies is an important part of host defenses. Humans and closely relate d primates, but not other mammals, possess natural anti-Gal alpha 1-3Gal an tibodies which also, although less avidly, react with melibiose (Gal alpha 1-6Glc). Using an enzyme-linked immunosorbent assay (ELISA) with melibiose bovine serum albumin as an antigen, we analyzed bovine anti-alpha galactosy l antibodies with respect to specificity and distribution in individual ani mals. Inhibition assays showed that melibiose was the strongest inhibitor, followed equally by stachyose (Gal alpha 1-6Gal alpha 1-6Glc beta 1-2Fru) a nd raffinose (Gal alpha 1-6Glc beta 1-2Fru) and then by Gal beta 1-6Gal, Ga l, and Gal alpha 1-2Gal, Others, including Gal alpha 1-3Gal and Gal alpha 1 -4Gal, only exhibited minor inhibition. Thus, these bovine anti-alpha galac tosyl antibodies appeared to preferentially react with Gal alpha 1-6Glc or Gal alpha 1-6Gal. The distinction of this specificity from that (Gal alpha 1-3Gal) of human antibodies was further demonstrated by the poor reaction o f bovine serum to the Gal alpha 1-3Gal antigen in comparison to human serum . All 27 healthy bovine serum samples of the three age groups (newborn, cal f, and adult) tested contained such antibodies with titers increasing with age. The antibodies purified by affinity chromatography using a melibiose-a garose column were mainly of the immunoglobulin G (Igc) isotype with a conc entration of >23 mu g/ml in most samples. IgG1 was found to be the primary antimelibiose Ige isotype in all age groups by isotype-specific ELISA, but a significant increase in IgG2, an isotype more related to innate immunity, was observed in calves and adults, compared to newborns, The purified anti bodies reacted with the type II bovine strain of Streptococcus agalactiae, a common pathogen of bovine mastitis. Thus, these anti-Gal alpha 1-6Glc or Gal alpha 1-6Gal antibodies in cattle might be involved in defense against microbes bearing this or the related epitopes.