The Complex Role of Regulatory T Cells in Immunity and Aging.

The immune system is a tightly regulated network which allows the development of defense mechanisms against foreign antigens and tolerance toward self-antigens. Regulatory T cells (Treg) contribute to immune homeostasis by maintaining unresponsiveness to self-antigens and suppressing exaggerated immune responses. Dysregulation of any of these processes can lead to serious consequences.

CD28 and CD57 define four populations with distinct phenotypic properties within human CD8 T cells.

After repeated antigen exposure, both memory and terminally differentiated cells can be generated within CD8 T cells. Although, during their differentiation, activated CD8 T cells may first lose CD28, and CD28 cells may eventually express CD57 as a subsequent step, a population of CD28 CD57 (DP) CD8 T cells can be identified in the peripheral blood. How this population is distinct from CD28 CD57 (DN) CD8 T cells, and from the better characterized non-activated/early-activated CD28 CD57 and senescent-like CD28 CD57 CD8 T cell subsets is currently unknown.

CD8HLADR Regulatory T Cells Change With Aging: They Increase in Number, but Lose Checkpoint Inhibitory Molecules and Suppressive Function.

CD4 regulatory T cells have been intensively studied during aging, but little is still known about age-related changes of other regulatory T cell subsets. It was, therefore, the goal of the present study to analyze CD8human leukocyte antigen-antigen D related (HLADR) T cells in old age, a cell population reported to have suppressive activity and to be connected to specific genetic variants. We demonstrate a strong increase in the number of CD8HLADR T cells with age in a cohort of female Sardinians as well as in elderly male and female persons from Austria.