Kinetics of immune cell reconstitution predict survival in allogeneic bone marrow and G-CSF-mobilized stem cell transplantation

The clinical utility of monitoring immune reconstitution after allotransplant was evaluated using data from Blood and Marrow Transplant Clinical Trials Network BMT CTN 0201 (NCT00075816), a multicenter randomized study of unrelated donor bone marrow (BM) vs granulocyte colony-stimulating factor (G-CSF)-mobilized blood stem cell (G-PB) grafts. Among 410 patients with posttransplant flow cytometry measurements of immune cell subsets, recipients of G-PB grafts had faster T-cell reconstitution than BM recipients, including more naive CD4(+) T cells and T-cell receptor excision circle-positive CD4(+) and CD8(+) T cells at 3 months, consistent with better thymic function. Faster reconstitution of CD4(+) T cells and naive CD4(+) T cells at 1 month and CD8(+) T cells at 3 months predicted more chronic graft-versus-host disease (GVHD) but better survival in G-PB recipients, but consistent associations of T-cell amounts with GVHD or survival were not seen in BM recipients. In contrast, a higher number of classical dendritic cells (cDCs) in blood samples at 3 months predicted better survival in BM recipients. Functional T-cell immunity measured in vitro by cytokine secretion in response to stimulation with cytomegalovirus peptides was similar when comparing blood samples from BM and G-PB recipients, but the degree to which acute GVHD suppressed immune reconstitution varied according to graft source. BM, but not G-PB, recipients with a history of grades 2-4 acute GVHD had lower numbers of B cells, plasmacytoid dendritic cells, and cDCs at 3 months. Thus, early measurements of T-cell reconstitution are predictive cellular biomarkers for long-term survival and response to GVHD therapy in G-PB recipients, whereas more robust DC reconstitution predicted better survival in BM recipients.