Disturbance in the reconstitution of distinct T-cell subsets and the incidence of GvHD following allo-HSCT in pediatric patients with non-malignant hematological disorders.

• Increased naïve T-cells in the CD4 T-lymphocyte population. • Increased TEMRA (effector memory T-cells that re-express CD45RA) cells in the CD8 T-cell population. • Treg:Tcons and Treg:CD8 ratios in patients with chronic G v HD. • Impaired reconstitution of distinct CD4 and CD8 T-cell subsets and their imbalance with Tregs may be involved in developing acute and chronic G v HD. The reconstitution of different T-cell subsets following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is critical for efficient pathogen protection and the prevention of graft-versus-host disease (G v HD). In particular, studies have highlighted the importance of balanced ratios of regulatory T-cells (Tregs) and distinct functionally T-cells in preventing acute and chronic G v HD. We evaluated the regeneration of CD4 and CD8 T-cell subpopulations in nine pediatric patients with non-malignant disorders following allo-HSCT from a fully HLA-identical donor. CD4 and CD8 T-cells were higher 12 months after the transplant but still lower than in healthy controls and pre-transplant. However, we found after allo-HSCT, central memory and effector memory cell subsets were the predominant phenotypes in the CD4 and CD8 T-cell populations, respectively. In patients who had developed acute G v HD, there was an increase in the frequency of TEMRA (effector memory T cells that re-express CD45RA) cells within the CD4 T-cell population. Meanwhile, in patients with chronic G v HD, we observed a decrease in Th1 cells in CD4 T-cells and effector memory cells within the CD8 T-cell population. In addition, we found decreased TEMRA cell subsets in CD4 and CD8 T-cell populations in chronic G v HD. Our findings suggest a possible relationship between the influence of acute G v HD and its prevention on delayed CD4 T-cell reconstitution and, reciprocally, unbalanced regeneration of CD4 and CD8 T-cell subsets in the development of chronic G v HD. [ABSTRACT FROM AUTHOR]