Studies on the precipitin content of bovine sera prepared against various biotypes of Brucella abortus.

The precipitin content of bovine antisera prepared against various biotypes of , including the vaccine strain S19, was examined by means of the double diffusion test in agar gel in an attempt to demonstrate differences, if present, in the soluble antigenic components of . It was shown that apart from a partial difference on two antigenic molecules, the virulent biotypes shared the soluble antigens demonstrated in the vaccine strain. The latter, however, was void of a component present in all the virulent biotypes examined. This extra soluble antigen of the virulent strains appeared to be only moderately antigenic in the different individuals of the bovine species. The implications of the findings are discussed.