Bovine immunoglobulins and brucellosis. IV. Study by microchromatographic technique of class types of persistent antibodies found in heifers vaccinated 12 to 14 months previously with Brucella abortus strain 19.

Microchromatography with Biogel A 1.5 is proposed to distinguish IgM and IgG antibodies present in biological fluid. The technique allows, with only simple material, a complete separation of the two classes in two hours, with a sample volume of less than 1 ml. The technique, applied to the study of sera from heifers vaccinated 12 to 14 months beforehand with B. abortus strain 19 demonstrated that the persistent antibodies were nearly exclusively of IgM type in animals retaining an agglutinating titre of more than 30 units. Since the sera of chronically infected animals are classically IgG type, this type of analysis could provide good evidence of vaccination or infection origin of residual agglutinins.