[Contribution of cytology and lymphocyte phenotyping in the biological diagnosis in infectious mononucleosis due to Epstein-Barr virus].

Because infectious mononucleosis is characterized by a T cell proliferation reacting with EBV-infected lymphocytes, we studied the changes in the blood cell counts and in the immunophenotype of the lymphocytes during this infection. The laboratory findings were similar for the different age groups, except in children less than 5 years old in whom we found a significantly less intense CD8+ S6F1+ response. According to this study, virus-specific serodiagnostic tests rarely show evidence of an acute primary EBV infection if the peripheral blood analysis fails to reveal significant changes in the leucocyte counts and in the T lymphocyte profiles. The study of this hematologic picture is a useful tool for the confirmation of infectious mononucleosis; moreover, it could greatly help when diagnostic problems occur.