ANTIBODY RESPONSES IN MYCOPLASMA PNEUMONIAE INFECTION IN RELATION TO SERUM IMMUNOGLOBULINS, ESPECIALLY IgM

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Abstract
Comparison of the antibody response to M. pneumoniae in patients with pneumonia of different ages showed that most cases below 20 years had an early predominance of IgM relative to IgG complement fixing (CF) antibodies whereas most adults above 40 years possessed more IgG than IgM CF antibodies. Young patients usually developed higher titres of CF than of tetrazolium reduction inhibiting (TRI) antibodies while older patients often showed higher TRI than CF antibody titres. 7 out of 10 adult patients with excretion of M. pneumoniae of short duration formed little or no IgM antibodies while most cases with prolonged excretion had a rather potent IgM antibody response in the early phase of infection. But a longlasting persistence of M. pneumoniae in the throat was not necessarily accompanied by a longlasting IgM antibody response. The total serum IgM level increased during infection in patients who developed high or moderate titres of IgM antibodies to M. pneumoniae and of cold agglutinins but showed little or no change in patients who formed M. pneumoniae antibodies of IgG class almost exclusively. Absorption with M. pneumoniae organisms of 8 sera with elevated IgM resulted in a 8—34 per cent reduction of total IgM. Removal of the cold agglutinins reduced the IgM concentration by 11 per cent in one serum but had little or no effect on the IgM level in 7 other sera. Absorbable M. pneumoniae antibodies and cold agglutinins accounted for 30—57 per cent of the IgM increase which was demonstrated during the infection. Two to four years after M. pneumoniae pneumonia, CF antibodies persisted in 38 out of 41 cases, TRI antibodies in 39 of 41 cases and IFL antibodies of IgG class in all of 41 cases. 50 per cent of the sera obtained 4 years after infection contained IgM antibodies demonstrable by IFL and CF.