Agglutinins against human erythrocytes modified by Newcastle disease virus in Mycoplasma pneumoniae infections.

Agglutinins against human group O erythrocytes modified by Newcastle disease virus (NDV-O agglutinins) showed a four-fold or greater rise in titre in 43% of sera from patients with Mycoplasma pneumoniae infection as opposed to 4% of patients with miscellaneous virus infections. The highest titres in Mycoplasma infection were only slightly lower than the highest titres in infectious mononucleosis, a disease known to be associated with NDV-O agglutinins. In Mycoplasma infection, both NDV-O agglutinins and cold agglutinins were more frequent in the younger patients. Analysis of the results by age groups suggested some additional association between NDV-O agglutinins and cold agglutinins independent of age.