Cytotoxic lymphocytes in infectious mononucleosis.

Seven patients with a clinical diagnosis of infectious mononucleosis (IM) and detectable heterophil antibodies were found to have peripheral blood lymphocytes that were cytotoxic for lymphoid cells containing Epstein-Barr virus from a patient with Burkitt's lymphoma. The cytotoxic lymphocytes persisted in the peripheral circulation for up to 45 days. Patients who had had IM 1 to 5 years previously lacked such cytotoxic lymphocytes. Patients who had signs and symptoms of IM but no detectable heterophil antibodies lacked cytotoxic lymphocytes. The lymphocytes of one patient with IM showed progressive diminution of cytotoxic ability after prednisone treatment.