Ex vivo T-cell-depleted allogeneic stem cell transplantation for hematologic malignancies: The search for an optimum transplant T-cell dose and T-cell add-back strategy.

Background: T-cell depletion (TCD) of allogeneic stem cell transplants (SCT) can reduce graft-versus-host disease but may negatively affect transplant outcome by delaying immune recovery. To optimize TCD in HLA-matched siblings with hematologic malignancies, we explored varying the transplant CD3+ T-cell dose between 2 and 50 × 10/kg (corresponding to 3-4 log depletion) and studied the impact of 0-6 × 10/kg CD3+ donor lymphocyte infusion (DLI) "add-back" on immune recovery post-SCT.

Methods: Two hundred seventeen consecutive patients (age range, 10-75 years) with hematologic malignancy (excluding chronic leukemias) underwent ex vivo TCD SCT from HLA-identical sibling donors from 1994-2015.