PREVENTION OF ADVERSE CLINICAL OUTCOME BY MONITORING OF CARDIAC TRANSPLANT PATIENTS FOR MURINE MONOCLONAL CD3 ANTIBODY (OKT3) SENSITIZATION

Abstract

We have previously reported that patients sensitized to murine monoclonal CD3 antibody (OKT3) and maintained on such therapy for induction of immunosuppression have a high mortality and/or allograft loss. In this follow-up study, we retrospectively reviewed all patients routinely and serially monitored by flow cytometry for plasma levels of OKT3 during a 21-month period beginning 1/90. A total of 112 patients were monitored during this period. We retrospectively tabulated the incidence of OKT3 sensitization, rejection pattern and impact on survival of withdrawal of OKT3 at the time of sensitization as compared with the previous study in which withdrawal was not done. Nine patients were excluded from analysis because of withdrawal for reasons other than sensitization: cytokine encephalopathy, infection, postoperative complications, or severe rejection. Twelve patients had OKT3 therapy aborted because of failure to achieve steady-state OKT3 levels or because of decline in levels while on therapy. These patients were thus defined as being sensitized to OKT3. No patient was aborted because of return of CD3 cells in the blood. Only one of the 12 patients sensitized to OKT3 died. Of 91 patients with steady-state OKT3 levels, 6 had high plasma levels (> 1000 ng/ml) and 6 had low plasma levels (< 500 ng/ml). None of these patients had OKT3 therapy aborted and all are alive. Twelve of these 91 patients had successful retreatment with OKT3 for refractory rejection, indicating that absence of sensitization on induction predicts safety of retreatment with OKT3. We also examined the frequency of associated human antimouse antibody (HAMA) production using the blocking assay modified from Jaffers and Mayes. Only the sensitized patients exhibited a significant association with HAMA production (6/7 tested, P = 0.05) Classification of the rejection pattern of the sensitized patients confirmed our previous results: eight of 12 had vascular rejection and 4/12 had mixed rejection. These patterns were prospectively determined. We conclude that serial monitoring of patients for plasma levels of OKT3 is an effective strategy to prevent adverse outcomes of induction with this agent.