Treatment of donor bone marrow with OKT3 (PAN-T monoclonal antibody) for prophylaxis of graft-vs.-host disease (GvHD) in histocompatible allogeneic bone marrow transplantation (BMT): A pilot study

Ten consecutive patients ranging in age from 7 to 34 years undergoing bone marrow transplantation from histocompatible siblings for treatment of hematologic malignancy were entered into a pilot study designed to test the safety of OKT3 pretreatment of donor bone marrow for prevention of graft-vs.-host disease. Concentrated donor bone marrow specimens containing a mean of 6.5 x 10⁸ nucleated cells/kg recipient weight were treated with 1 mg of OKT3 at 4°C for 30 min prior to administration to the recipient. In vitro immunofluorescent studies confirmed that all OKT3⁺ cells in bone marrow had effectively bound antibody. Furthermore, the addition of neonatal rabbit complement in vitro decreased the proliferative responses of donor bone marrow cells to phytohemagglutinin and concanavalin A (Con A) to ≤4% of untreated bone marrow. No significant complications resulted from the administration of OKT3 and all recipients engrafted after a mean duration of 22 days. Nine of the 10 patients survived for more than 100 days after marrow transplantation. However, 5 of the 10 patients developed acute graft-vs.-host disease and required steroid therapy. While this pilot study suggests that OKT3 can be used safely in the bone marrow transplantation setting, further modification of our OKT3 treatment procedure will be necessary to completely eradicate graft-vs.-host disease in histocompatible bone marrow transplantation.