Anti-i in infectious mononucleosis.

Abstract

Anti-i appears frequently as an autoantibody in the blood of patients with infectious mononucleosis, but rarely results in autoimmune hemolytic anemia. This report deals with such a case and with the incidence of anti-i in patients without hemolytic anemia. The antibodies reacted best in the cold. In the patient with hemolytic anemia, the titer was 1:1,024 with cells of cord blood and 1:64 with normal adult blood cells, including the patient's own. About three weeks after the patient's recovery the antibodies were barely detectable by cells of cord blood, although a significant titer of heterophil agglutinins was still present. The incidence of anti-i agglutinins among 52 patients with uncomplicated infectious mononucleosis was found to be 69.2%. The serum of only one of the patients had a significant titer, whereas the vast majority had low titers and avidity for cells of cord blood. None reacted with normal adult cells at 37 C, but three reacted weakly at 4 C. Sera from 12 of the 52 patients who had recovered were retested for anti-i four to six weeks after onset of symptoms. All showed complete disappearance of the anti-i antibodies. It was concluded that anti-i shows a better correlation with the hemolytic and other complications of infectious mononucleosis than with heterophil agglutinins. No anti-i antibodies were detected in 23 sera screened for their presence.