Cells containing Epstein--Barr nuclear antigen (EBNA) in peripheral blood.

The anti-complement immunofluorescence (ACIF) method was used to demonstrate EBNA in B lymphocytes separated from the peripheral blood of patients with infectious mononucleosis (IM) or other diseases. In the acute phase of IM of Epstein-Barr virus (EBV) origin, 0.5--1% of the B lymphocytes proved to be positive in 6 of the 8 patients tested. In two of the positive cases the test was repeated 20 and 26 days, respectively, after clinical symptoms had appeared; the result was negative in both cases. No EBNA-positive cells were found in the peripheral blood of 17 patients with Hodgkin disease, 3 with systemic lupus erythematosus and 2 with lymphosarcoma. It is supposed that EBNA-positive cells appear in detectable amount exclusively in the acute phase of EBV infection.