The use of ion exchange chromatography for demonstration of rubella-specific IgM antibodies

IgM and IgG immunoglobulins of human sera were separated by stepwise column chromatography in QAE-Sephadex A-25 ion exchanger gel bed. The procedure resulted within 30 min in a fraction suitable for direct titration of rubella-specific IgM antibodies by haemagglutination inhibition test. The method proved to be a useful diagnostic tool for primary rubella. Serum samples of 13 individuals with previously acquired immunity, 152 patients with a recent rubella-like illness, and 194 pregnant women exposed to rubella infection were tested for the presence of rubella-specific IgM antibodies. Sera of individuals with previous immunity proved to be negative for specific IgM antibodies. Specific IgM titre was demonstrated in the blood of all the 25 patients with significant titre-rise tested because of rubella-like illness, and also in the sera of additional 8 patients whose serum samples were taken too late for demonstration of a rise in titre. Significant titre-rises were found in 5 women exposed to rubella infection, but only two of them exhibited rubella-specific IgM antibodies. The absence of specific IgM antibodies refers presumably to subclinical reinfection in the other three cases.