Specific secondary biological properties of purified rabbit immunoglobulin M and immunoglobulin G antibodies to Brucella abortus and Bordetella pertussis.

Rabbit immunoglobulin (Ig)M and IgG antibodies to Brucella abortus and Bordetella pertussis were isolated as purified products and their specific secondary biological activities were compared. IgM antibodies were found to be more active than IgG proteins in inducing agglutination and sensitization of B. abortus for the complement-dependent bactericidal effect and in inhibiting B. pertussis-induced lymphocytosis in the mouse. IgM and IgG antibodies were found to be equally effective in inducing agglutination of B. pertussis suspended in a colloidal solution. These data parallel previous work to indicate that IgM antibodies to bacterial surface antigens are more efficient than IgG molecules in initiating biological processes concerned with the inactivation of these pathogens.