Changes in erythrocyte I agglutinogen and anti-I-agglutinins during Mycoplasma pneumoniae infection in man

Changes in the erythrocyte I agglutinogen and in serum anti-I agglutinins were studied following experimental infection of 27 adult volunteers with Mycoplasma pneumoniae. An increase in thermal amplitude of anti-I agglutinins developed in 12, among whom seven had simultaneous rises in titer of cold agglutinins. The activity of the erythrocyte I agglutinogen was transiently reduced following M. pneumoniae infection in five of the volunteers. These changes were not associated with clinical or laboratory evidence of hemolytic anemia. The possibility that M. pneumoniae organisms directly altered the erythrocyte I antigen leading to the production of anti-I antibodies is discussed.