Infectious mononucleosis]

Infectious mononucleosis(IM) is a primary Epstein-Barr virus (EBV)infection. Since heterophil antibody negative IM is common in Japan, EBV antibody(presence of VCA-IgM or anti-EA, high titers of VCA-IgG in the absence of anti-EBNA) is useful for serologic diagnosis of IM. Although EBV causes the continuous growth of lymphoid cell lines in vitro and causes malignant diseases such as Burkitt lymphoma, nasopharyngeal cancer and malignant lymphomas in immunocompromised patients, IM is usually self-limiting, and after primary infection EBV persists in B cells throughout life without producing symptoms. In the present study, we studied CD8+ lymphocytes of patients with IM and demonstrate an increase in lymphocytes expressing HLA-DR and CD45RO, increase of intracellular pH, elevated plasma levels of sCD8, indicating activation of the subset. We also demonstrate activation of CD4+ T lymphocytes and gamma delta T lymphocytes. Activation of these immune systems in response to EBV is supposed to play an important role in assuring the benign course of IM.