FAILURE OF A CD18/ANTI-LFAl MONOCLONAL ANTIBODY PATIENTS RECEIVING T-DEPLETED ALLOGENEIC BONE INFUSION TO PREVENT GRAFT REJECTION IN LEUKEMIC MARROW TRANSPLANTATION

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Abstract
CD18 antibodies react with the common beta chain of the human leukocyte function antigen (LFA1)* and thus block the functions mediated by the three identified molecules in humans. A murine CD18 monoclonal antibody was infused in 8 leukemic patients receiving allogeneic T-depleted bone marrow transplantation in order to prevent graft rejection. This was part of the conditioning, including total-body irradiation and high-dose chemotherapy, given to all patients. To prevent graft-versus-host disease the donor bone marrow T cells were depleted using complement-mediated cytolysis or a ricin A conjugate immunotoxin, and cyclosporine or methotrexate were given posttransplant. A persistent level of free circulating anti-LFA1 antibody was detected in 5/8 patients. Despite this, 5 graft failures occurred, with 2 patients experiencing late rejection (days 60 and 97) following HLA-identical transplantation and 3 patients having no engraftment following haplo-mismatched transplant. One other patient died of early sepsis. Only 2 patients (who differed at 1 HLA locus from their donor) are alive with long-term complete chimerism (300 and 315 days). Transient inhibition of recipients'' leukocyte functions with an anti-LFA1 antibody did not appear to facilitate engraftment of allogeneic T-depleted marrow transplantation for leukemias.