Cell-Mediated Immunity to Epstein–Barr-Virus-Transformed Lymphoblastoid Cells in Acute Infectious Mononucleosis

Abstract

Mononuclear peripheral blood leukocytes from 21 patients with infectious mononucleosis and 16 healthy controls were tested in a ⁵¹Cr-release assay for cytotoxicity against two human lymphoblastoid cell lines derived from the same donor. One line contained the Epstein–Barr virus (EBV); the other did not. acute-phase leukocytes were significantly more cytotoxic against the EBV-infected cell line than were control leukocytes. Mean (±S.E.) lysis at a leukocyte-target-cell ratio of 100:1 was 10.6±1.6 per cent for patients and 3.4 ± 0.6 per cent for controls (P < 0.0005). Cytotoxicity correlated with the percentage of atypical lymphocytes. Cells of three patients with acute mononucleosis-like illnesses failed to show killing activity above those of normal controls. Cytotoxicity against the EBV-negative line was not significantly different for each group. The finding of cytotoxic cells in infectious-mononucleosis patients with atypical lymphocytes suggests that these cells operate in vivo to limit the proliferation of altered EBV-transformed B lymphoblasts. (N Engl J Med 293:1159–1163, 1975)