Lymphocyte subsets and natural killer cell responses during cytomegalovirus mononucleosis.

Cell-mediated immunity in seven patients with cytomegalovirus mononucleosis was assessed by monoclonal antibody to lymphocyte subsets, lymphocyte blastogenesis, and natural killer cell activity. The patients had decreased ratios of helper (Leu 3a) to suppressor-cytotoxic (Leu 2a) T cells as compared with normal donors. Leu 2a+ T cells from the patients were uniquely sensitive to overnight culturing, which resulted in a 2.6-fold increase in the helper/suppressor cell ratio and the appearance of an unusual third Leu 1+ 2a- 3a- T cell subset. This correlated directly with enhanced blastogenesis to concanavalin A after preculture. Base-line and interferon-boosted natural killer cell responses versus K562 cell targets during cytomegalovirus mononucleosis did not differ from those of normal donors. This suggests that certain cellular immune functions are depressed during cytomegalovirus mononucleosis in correlation with the emergence of a culture-sensitive subset of suppressor T cells. In contrast, cytotoxic lymphocytes appear to function normally and may aid in the resolution of the illness.