DEVELOPMENT OF ANTI-OKT3 ANTIBODIES AFTER OKT3 TREATMENT

The development of IgG and IgM anti-OKT3 antibodies the first 90 days after start of OKT3 treatment for acute cellular rejection was determi ned by ELISA in 25 consecutive renal transplant patients. The ELISA po sitive sera were then tested for neutralizing OKT3 antibodies by immun ofluorescence inhibition assay utilizing the FACScan. The number of Ig M positive patients was highest, four (16%) after 10 days of treatment and then declined. The highest number of patients, thirteen (56%) wit h IgG antibodies was found after 60 days. Sera with only IgM antibodie s or with low IgG titers (<1:100) did not neutralize OKT3. Five patien ts (20%) developed neutralizing antibodies. All of these patients had received OKT3 during an earlier transplantation. In four of these pati ents, the ACR had been reversed successfully before the development of antibodies, and in the last patient the ACR was reversed by a second course of Minnesota-ALG and increasing the dose of Cyclosporine. Monit oring the development of neutralizing anti-OKT3 antibodies is valuable in patients who have previously received OKT3 treatment.