Immediate loss of cell-mediated immunity to murine cytomegalovirus upon treatment with immunosuppressive agents.

Splenic lymphocytes from cytomegalovirus-infected mice lost their in vitro proliferative responses to cytomegalovirus antigen within 3 h after in vivo treatment with antilymphocyte globulin and prednisolone. The response was inhibited when the agents were administered separately or together, and inhibition persisted through a 2-week course of immunosuppression. Circulating specific antibodies were depressed by multiple injections of antilymphocyte globulin alone or with prednisolone, but not by prednisolone alone. Mitogen-induced blast transformation was immediately depressed by immunosuppression with both agents. Although the response to lipopolysaccharide returned briefly, it declined with continuing treatment. Cytomegalovirus infection augmented the depressive effect of immunosuppression on the lipopolysaccharide proliferative response. Prednisolone treatment of infected animals did not affect the concanavalin A response, and lipopolysaccharide stimulation decreased more slowly and to a lesser extent than it did in mice treated with antilymphocyte globulin or both agents. Loss of specific cell-mediated immunity and simultaneous depression of humoral immunity indicated that immunosuppression immediately created an inability to respond to an active cytomegalovirus infection.