Elderly individuals exhibit unbalanced bone marrow (BM) effector T cell subset differentiation, such as increased T helper (Th)-1 and T cytotoxic (Tc)-1 cell frequencies, but the underlying mechanism still unclear. Endothelial cells (ECs) , which are instructive components of the BM microenvironment, exhibit the phenotype of semi-professional antigen-presenting cells and regulate T cell recruitment and activation. Thus, we compared the frequency and function of BM ECs, especially their capacity to regulate effector T cell subsets, between young and old healthy individuals, and explored the underlying mechanism of this immunomodulatory discrepancy. Although the young and old EC percentages were comparable, young ECs showed less reactive oxygen species and better migratory and tube-forming abilities than old ECs. Notably, young ECs regulated T cells to differentiate into fewer Th1 and Tc1 cells than old ECs. Reduced T cell activation molecules and inflammatory cytokines in young BM ECs may be the possible mechanism.
