Specificity and prevalence of natural bovine antimannan antibodies

Immune responses to the carbohydrate components of microorganisms, mediated both by antibodies and by lectins, are an important part of host defense. In the present experiments, the specificity and presence of natural bovine antibodies against mannan, a common fungal antigen, were examined by enzyme -linked immunosorbent assay (ELISA), using Saccharomyces cerevisiae mannan as an antigen. The results showed that all serum samples from animals of th ree age groups (newborn, calf and adult) tested contained antimannan antibo dies, and the titer of these antibodies increased significantly in adults. However, titers among individual adult cattle differed widely. Inhibition a ssays showed that yeast mannan was the strongest inhibitor. D-Mannose exhib ited only a minor inhibitory effect at high concentrations. This suggests t hat most of these antibodies recognize an oligosaccharide-based epitope(s) different from those recognized by lectins. Cattle possess three serum C-ty pe lectins (collectins) capable of recognizing mannan in a calcium-dependen t manner.; Addition of EDTA to the reaction did not reduce antibody binding , suggesting that the binding of these antibodies to mannan was not affecte d by the presence of collectin. The antibodies purified from either calf or adult serum by mannan-Sepharose affinity chromatography consisted of mainl y immunoglobulin G (IgG) and a smaller amount of IgM. IgG1 was shown to be the dominant antimannan Ige isotype by isotype-specific ELISA. Together, th ese results demonstrate the production of natural antimannan antibodies in cattle in an age-dependent manner. These antibodies might be involved in de fending the host against mannan-containing pathogens as a specific line of defense in conjunction with the innate response by lectins.