Selective Depletion of Bone Marrow T Lymphocytes With Anti-CDS Monoclonal Antibodies: Effective Prophylaxis for Graft-Versus-Host Disease in Patients With Hematologic Malignancies

Seventy-one patients with hematologic malignancies received bone marrow from a histocompatible sibling (n = 48) or a partially matched relative (n = 23) that had been depleted of CD5’ T cells with either an anti-CD5 monoclonal antibody (MoAb) plus complement (anti-Leu1 + C) or an anti-CD5 MoAb conjugated to ricin A chain (ST1 immunotoxin [STl-IT]). These patients received intensive chemoradiotherapy consisting of cytosine arabinoside, cyclophosphamide, and fractionated total body irradiation. Both antiLeu1 + C and ST1-IT ex vivo treatments effectively depleted bone marrow of T cells (97% and 95%. respectively). Overall, primary and late graft failure each occurred in 4% of evaluable patients. The diagnosis of myelodysplasia was a significant risk factor for graft failure (P < .001), and if myelodysplastic patients were excluded, there were no graft failures in major histocompatibility complex (MHC)-matched patients and 2 of 23 (8.7%) in MHC-mismatched patients. The actuarial risk of grade 2 to 4 acute graft-versus-host disease (GVHD)