Antibody development in pigs inoculated with live or killed cultures of Brucella abortus.

As shown by density gradient ultracentrifugation and column chromatography, pigs formed IgM antibodies during the first week following vaccination with Brucella abortus, strain 19. At this time their sera reacted in both plate and tube agglutination but not in complement-fixation tests. A few days later, when IgG antibodies had developed, agglutination titers were still high and some activity was recorded in hemolytic complement-fixation tests. A similar sequence was observed in pigs repeatedly inoculated with phenol-killed suspensions of B. abortus. As the proportion of IgM to IgG antibodies decreased, agglutinin titers fell in relation to complement-fixing titers. In some animals the conglutinating complement absorption test became positive earlier than the plate agglutination.