Mechanisms of immunosuppression in cytomegalovirus mononucleosis. II. Virus-monocyte interactions.

Virus-monocyte interactions were evaluated in patients with mononucleosis due to cytomegalovirus (CMV). Group 1 patients studied about two weeks after the onset of symptoms had lymphocyte responses to concanavalin A (con A) that were maximally suppressed and unaffected by in vitro culture or reconstitution with monocytes. Lymphocytes from group 2 patients studied about three weeks after the onset of symptoms had less markedly suppressed responses, which were reversed by in vitro culture or by reconstitution with monocytes. Monocyte depletion resulted in a marked diminution of fresh lymphocyte responses of group 2 patients but not of group 1 patients. CMV was isolated from blood monocytes of four patients with mononucleosis; intact, infected monocytes were capable of suppressing responses of cultured autologous lymphocytes to con A. Monocytes from uninfected control donors were infected in vitro with CMV and evaluated for the induction of suppressor activity. CMV-infected monocytes were significantly more suppressive for autologous lymphocyte responses to con A than were uninfected monocytes.