Improved function and balance in T cell modulation by endothelial cells in young people.

Elderly individuals exhibit unbalanced bone marrow (BM) effector T cell subset differentiation, such as increased T helper type 1 (Th1) and T cytotoxic type 1 (Tc1) cell frequencies, but the underlying mechanism is 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 elderly healthy individuals, and explored the underlying mechanism of this immunomodulatory discrepancy. Although the young and elderly EC percentages were comparable, young ECs showed fewer reactive oxygen species and better migratory and tube-forming abilities than elderly ECs. Notably, increased T cell activation molecules and inflammatory cytokines were found in elderly ECs which regulated T cells to differentiate into more proinflammatory T cells, including Th1 and Tc1 cells, than young ECs.