Phenotypic Properties of Atypical Lymphocytes in Cytomegalovirus-Induced Mononucleosis

The phenotypic properties of the surface of the atypical lymphocytes seen in cytomegalovirus-induced(CMV)mononucleosis were evaluated. Mononuclear cells from peripheral blood were obtained from adult patients within seven to 35 days of the onset of acute CMV mononucleosis. Sheep red blood cell rosetting techniques were used to obtain populations depleted of, or enriched for, T cells. Cell populations were further purified for helper/inducer lymphocytes(T4), cytotoxic/suppressor lymphocytes(T8), or non-T lymphocytesby monoclonal-antibody binding and by complement-lysis techniques. Cytocentrifuge preparations of the cell fractions were evaluated and atypical lymphocytes were identified by morphological characteristics. The appearance and disappearance of atypical lymphocytes paralleled and antedated the increase and subsequent decrease in T8 cells seen in these patients. A total of 69% ± 22% of the atypical lymphocytes in the lymphocyte population were of the T8 phenotype, whereas 13% ± 10% of the atypical lymphocytes were of the T4 phenotype and 18% ± 13%were non-T lymphocytes. Thus, atypical lymphocytes in CMV mononucleosis reside predominantly, but not exclusively, in the T8 cell population.