Increased Type 1 Immune Response in the Bone Marrow Immune Microenvironment of Patients with Poor Graft Function after Allogeneic Hematopoietic Stem Cell Transplantation

Poor graft function (PGF) is a severe complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The question of whether the bone marrow (BM) immune microenvironment is involved in the pathogenesis of PGF remains unresolved. In total, 10 patients with PGF, 30 matched patients with good graft function after allo-HSCT, and 15 healthy donors were enrolled in this nested case-control study. The Th1, Th2, Tc1, Tc2, and active phenotypes were analyzed by flow cytometry. IFN-γ and IL-4 levels in BM plasma were evaluated using cytometric beads assay. Relative to other subjects, patients with PGF had significantly higher proportions of stimulated CD4+ and CD8+ T cells that produced IFN-γ (Th1 and Tc1 cells) but notably decreased proportions of IL-4-producing T cells (Th2 and Tc2 cells), resulting in a shift of the IFN-γ/IL-4 ratio towards a type 1 response and an elevated percentage of activated CD8+ T cells. Changes in IFN-γ and IL-4 levels in BM plasma were consistent with the cellular results. Our results suggest that dysregulated T cell responses may contribute to the occurrence of PGF after HSCT.