Unique antithymocyte serum versus OKT3 for induction immunotherapy after heart transplantation.

To determine the efficacy of a unique polyclonal rabbit antithymocyte serum (ATS), we compared 17 consecutive nonrandomized heart transplant recipients (mean age, 38 +/- 15 years) given a 7-day prophylactic postoperative course of locally produced ATS (whole serum, no Freund's adjuvant, IV) with 19 patients (mean age, 42 +/- 17 years) given 14 days of monoclonal antibody OKT3. Cyclosporine, steroid, and azathioprine dosages were similar. At 30 days the event-free incidence of rejection was 66% +/- 11% for OKT3 (2.3 events/100 patient-days) versus 47% +/- 12% for ATS (1.2 events/100 patient-days). At 60 days and thereafter, however, there was no difference in overall number of cumulative rejection episodes. Overall infection rates were similar in both groups: the ATS group tended to have more bacterial infections, whereas the OKT3 group displayed more viral infections. Antiidiotypic antibodies developed in 29% of the ATS group and in 22% of the OKT3 group. This report demonstrates the efficacy of this polyclonal serum preparation made without Freund's adjuvant when used as an adjunct for induction-prophylactic immunotherapy in heart transplant recipients when compared with OKT3.