A simplified procedure for measuring the class of anti-bacterial antibodies by mixed reverse passive antiglobulin haemagglutination (MRPAH).

A modified procedure is described for performing the MRPAH (mixed reverse passive antiglobulin haemagglutination) reaction as a simple micro-method to measure the classes of bacterial antibodies. This 'bacterial dilution procedure' gave results closely correlated with those obtained by the 'serum (sample) dilution procedure' previously reported and with great economy of materials, labour and time. The method was used to investigate human serum antibodies to Br. abortus and S. enteritidis and serum and secretory antibodies to Strep. mutans. The good reproducibility of the MRPAH reaction was demonstrated by re-examining brucellosis sera tested one year previously. MRPAH was sufficiently sensitive to demonstrate the small amounts of IgG and IgM antibodies to Strep. mutans in human colostrum and early milk. A rise of antibody levels in the different immunoglobulin classes G, A and M was readily demonstrated in sera from individuals with salmonellosis.