Auto-antibodies in infectious mononucleosis, as determined by ELISA.

An increased incidence of abnormal values for anti-DNA, anti-deoxyribonucleoprotein (NP) and rheumatoid factor (RF) were found in heterophil antibody-positive infectious mononucleosis (IM). These positive auto-immune reactions were mostly at low levels. Those IM sera which revealed these auto-antibodies in the normal range showed mean values which were significantly higher than the mean values seen in normal sera. No correlation was found between the IM heterophil antibody levels and the concentrations of RF, anti-DNA or anti-NP. In the majority of cases, the anti-DNA and anti-NP responses in IM were predominantly of the IgM class.