Immunoaging induced by hematopoietic stem cell aging.

Hematopoietic stem cells (HSCs) generate all known hematopoietic lineages and self-renew, but the function of HSCs declines during aging, which is characterized as impairments of lymphopoiesis and enhanced myelopoiesis. These aging-associated changes correlate with an increasing risk of myelo-proliferative diseases and impairments in immune function. Recent studies showed that only a subpopulation of HSCs contains a high capacity to undergo lymphoid differentiation but this subpopulation is lost during aging, which contributes to age-related impairments in lymphopoiesis. On the basis of the observations that DNA damage and telomere dysfunction can impair stem cell function, it is possible that accumulation of DNA damage results in the loss of subpopulations of HSCs that are required for the maintenance of lymphopoiesis and immune functions during aging.