Robust CD4⁺ T-cell recovery in adults transplanted with cord blood and no antithymocyte globulin

Quality of immune reconstitution after cord blood transplantation (CBT) without antithymocyte globulin (ATG) in adults is not established. We analyzed immune recovery in 106 engrafted adult CBT recipients (median age 50 years [range 22-70]) transplanted for hematologic malignancies with cyclosporine/mycophenolate mofetil immunoprophylaxis and no ATG. Patients were treated predominantly for acute leukemia (66%), and almost all (96%) underwent myeloablation. Recovery of CD4⁺ T cells was faster than CD8⁺ T cells with median CD4⁺ T-cell counts exceeding 200/mm³ at 4 months. Early post-CBT, effector memory (EM), and central memory cells were the most common CD4⁺ subsets, whereas effector and EM were the most common CD8⁺ T-cell subsets. Naive T-cell subsets increased gradually after 6 to 9 months post-CBT. A higher engrafting CB unit infused viable CD3⁺ cell dose was associated with improved CD4⁺ and CD4⁺CD45RA1 T-cell recovery. Cytomegalovirus reactivation by day 60 was associated with an expansion of total, EM, and effector CD8⁺ T cells, but lower CD4⁺ T-cell counts. Acute graft-versus-host disease (aGVHD) did not significantly compromise T-cell reconstitution. In serial landmark analyses, higher CD4⁺ T-cell counts and phytohemagglutinin responses were associated with reduced overall mortality. In contrast, CD8⁺ T-cell counts were not significant. Recovery of natural killer and B cells was prompt, reaching medians of 252/mm³ and 150/mm³ by 4 months, respectively, although B-cell recovery was delayed by aGVHD. Neither subset was significantly associated with mortality. ATG-free adult CBT is associated with robust thymus-independent CD4⁺ T-cell recovery, and CD4⁺ recovery reduced mortality risk.