Immune Recovery in Adult Patients Following Myeloablative Dual Umbilical Cord Blood, Matched Sibling, and Matched Unrelated Donor Hematopoietic Cell Transplantation

Immunologic reconstitution following allogeneic hematopoietic cell transplantation (HCT) is a critical component of successful outcome. Umbilical cord blood (UCB) transplantation in adult recipients is associated with slow and often inadequate immune recovery. We characterized the kinetics and extent of immune recovery in 95 adult recipients following a dual UCB (n=29), and matched sibling (MSD) (n=33) or unrelated donor (MUD) (n=33) transplantation. All patients were treated with myeloablative conditioning. There were no differences in the immune recovery profile of MSD and MUD recipients. Significantly lower levels of CD3+, CD4+ and CD8+ T-cells were observed in UCB recipients until 6 months following transplantation. Lower levels of regulatory T-cells persisted until 1 year following transplantation. Thymopoiesis as measured by T-cell receptor rearrangement excision circle (TREC) was comparable among all recipients by 6 months following transplantation. In a subset of patients 1 year following transplantation with similar levels of circulating T-cells and TREC, there was no difference in T-cell receptor diversity. Compared to HLA-identical MSD and MUD adult HCT recipients, quantitative lymphoid recovery in UCB transplant recipients is slower in the first 3 months, but these differences disappeared by 6–12 months following transplantation.