Blood lymphocytes in infectious mononucleosis share the following characteristics with activated T cells: natural attachment, stable E rosetting and glucocorticoid sensitivity.

Blood lymphocytes of infectious mononucleosis (IM) patients, unlike these obtained from healthy individuals, exhibit the following characteristics of activated T cells: (1) "stable" E rosette formation; (2) natural attachment to various human normal and malignant cells; (3) sensitivity in vitro to the lytic effect of glucocorticoids. Although the IM T cells attach in vitro to all the human cells tested, they kill only the EBV genome carrying targets. The possibility is discussed that some of the activated T cells in IM result from a non-specific activation elicited by the T cells responding specifically to the EBV associated antigens.