Impaired lymphocyte transformation response to cytomegalovirus and phytohemagglutinin in recipients of renal transplants: association with antithymocyte globulin.

Cell-mediated immunity was assessed in 38 seropositive recipients of renal transplants by measuring the in vitro lymphocyte transformation response (LTR) to cytomegalovirus (CMV) and to phytohemagglutinin; results were correlated with clinical course, viral excretion, and immunosuppressive treatment. Thirteen seropositive controls all responded to CMV with a mean stimulation index of 31 +/- 6; 14 seronegative controls all had stimulation indices of less than 3. LTR to CMV was found to require both thymus-derived lymphocytes and macrophages. Before immunosuppression, responses of patients were similar to those of controls. After renal transplantation mean LTRs to CMV were dramatically reduced up to 18 months postoperatively, especially in patients treated with antithymocyte globulin. Viremia and CMV-related illness were significantly more frequent in recipients of antithymocyte globulin. Although there was only a rough correlation between clinical events and LTR to CMV, five deaths were noted among seven patients (all treated with antithymocyte globulin) who failed to respond to phytohemagglutinin on two consecutive tests.