The occurrence of autoantibodies in infectious mononucleosis.

Autoantibodies were looked for by immunofluorescence (IFL) in seventy-seven cases of infectious mononucleosis (IM) at the onset of symptoms and on recovery, to determine the time of appearance, duration and range of these responses, and to correlate them with serum immunoglobulin and EB virus antibody titres. Antibodies to lymphocyte membrane demonstrated by IFL, now identified with lymphocytotoxins, were present in 46% of patients in the acute stage, persisting for less than 7 weeks. Antibodies to smooth muscle (SMA) or to contractile fibres in other tissue cells including human thyroid and rat hepatocytes, were present in over 70% of cases, some being entirely of IgM class. The highest titres occurred soon after onset and these antibodies also disappeared during convalescence. By contrast ANA, mitochondrial, microsomal and reticulin antibodies, also thyroid and gastric organ-specific reactivity were seen only occasionally owing to the young age group of the patients. In individual cases there was no correlation between the appearance of lymphocyte antibodies and SMA, or between these and the EB virus antibody titres. The autoantibodies produced in this disease are highly selected. It is suggested that clones of B cells are stimulated to make these antibodies by virtue of being infected with EB virus, and that the T-cell clones in the circulation are more likely expanded in order to terminate the infection.