Increased numbers of cells with suppressor T cell phenotype in the peripheral blood of patients with infectious mononucleosis.

Peripheral blood cells from six patients with acute infectious mononucleosis were studied by two-colour immunofluorescence using antibodies to human T cells, inducer and suppressor-cytotoxic T cell subsets and Ia-like antigens. The absolute number of T cells with the suppressor-cytotoxic phenotype was substantially increased in each case; many of these cells also expressed Ia-like antigens and had the morphology of the large atypical cells characteristic of infectious mononucleosis. These activated suppressor T cells of infectious mononucleosis may therefore represent a control mechanism to prevent viral-induced proliferation of B cells.