Interleukin-2 receptors in infectious mononucleosis.

The majority of peripheral blood mononuclear cells (PBMC) from acute-phase infectious mononucleosis (IM) patients express high levels of T10 (CD38) and HLA-DR surface antigens, which are markers characteristic of activated T cells. However, Tac antigen (p55) expression on these cells was not detectable by flow cytometric immunofluorescence, and only a low level of specific interleukin-2 (IL-2) binding was found by Scatchard analysis. These results suggest that IL-2 receptors (IL-2R) are lost or down-regulated on activated T cells in acute IM. Since a large proportion of T cells die during the first 24 h of in vitro culture in the absence of exogenous IL-2, the data implicate a physiological role for the observed low levels of IL-2R on T cells.