Horse agglutinins in infectious mononucleosis TABLE I HORSE AGGLUTININ TITRES OF SERA HAVING SHEEP AGGLUTININ TITRES OF 14 OR LOWER Horse RBC TBA

SYNOPSIS One hundred infectious mononucleosis and the same number of non-infectious mononucleosis sera were studied to evaluate the sensitivity and specificity of horse erythrocytes in the diagnosis of infectious mononucleosis. Titres of horse agglutinins in infectious mononucleosis sera ranged from 28 to 7,168 with a geometric mean of 550, whereas the corresponding sheep agglutinin titres ranged from less than 7 to 3,584, with a geometric mean of 126. Horse agglutinin titres of non-infectious mononucleosis sera ranged from less than 7 to 896, with a geometric mean of 59. Infectious mononucleosis sera tested with horse erythrocytes before and after absorption with guinea pig kidney and beef erythrocytes showed patterns different from those of non-infectious mononucleosis sera, even when sheep agglutinin titres were too low for satisfactory evaluation. After absorption with guinea pig kidney, horse agglutinin titres of infectious mononucleosis sera were uniformly higher than in the corresponding serum absorbed with beef erythrocytes. This was not the case for non-infectious mononucleosis sera. Results confirm our previously expressed view that horse erythrocytes are preferable to sheep erythrocytes in the serological diagnosis of infectious mononucleosis.