IMMUNE RESPONSES IN MYCOPLASMA PNEUMONIAE INFECTIONS

Abstract

It was reported previously that serum antibodies against Mycoplasma pneumoniae mainly belonged to IgG and IgM and that these immunoglobulins appeared subsequently to infection with this organism. The ratio of IgG to IgM antibodies showed a considerable individual variation even when compared at approximately the same time after the onset of illness. There was no definite explanation for this individual variation.
The present study was carried out on the serum immunoglobulin response of children with M. pneumoniae infection, especially the chronological change of specific IgG and IgM titers measured by the indirect immunofluorescent (IMF) technique. The chronological change of IgG and IgM IMF titers was compared with that of complement-fixing (CF) and cold hemagglutination (CHA) antibody titers. Many patients showed an apparent subsequent appearance of IgG IMF antibody, and this appearance was similar to that of CF antibody. An individual variation was observed in specific IgG IMF antibody response and in the persistence of this antibody.
There were some patients who had no detectable IgM IMF antibody. All of them exhibited a significant rise in CF and IgG IMF titers. These results agreed with those obtained from some cases which responded to M. pneumoniae infection with the production of antibodies of IgG class almost exclusively. All those patients presented a significant change in titer of CHA antibody which belonged to the IgM class. The results agreed with those reported by previous authors that some patients showed an increase of nonspecific serum IgM level during infection with M. pneumoniae, whereas they had specific antibodies belonging almost exclusively to the IgG class. The patients studied in the present investigation included some who possessed preexisting specific antibody. An individual variation in IgM IMF antibody response was also proved in these patients. It was considered that the experience of reinfection with M. pneumoniae might have no important effect upon the individual variation, and that after the secondary immune response to M. pneumoniae infection IgM antibody might be detectable in some patients.