Skin T cells maintain their diversity and functionality in the elderly

Recent studies have highlighted that human resident memory T cells (T-RM) are functionally distinct from circulating T cells. Thus, it can be postulated that skin T cells age differently from blood-circulating T cells. We assessed T-cell density, diversity, and function in individuals of various ages to study the immunologic effects of aging on human skin from two different countries. No decline in the density of T cells was noted with advancing age, and the frequency of epidermal CD49a(+) CD8 T-RM was increased in elderly individuals regardless of ethnicity. T-cell diversity and antipathogen responses were maintained in the skin of elderly individuals but declined in the blood. Our findings demonstrate that in elderly individuals, skin T cells maintain their density, diversity, and protective cytokine production despite the reduced T-cell diversity and function in blood. Skin resident T cells may represent a long-lived, highly protective reservoir of immunity in elderly people. Koguchi-Yoshioka et al. demonstrate that functional activities and diversity of T cells are highly maintained in the skin of elderly people when compared with those in the blood regardless of the ethnicity of the participants or the experimental procedures. They also find the accumulation of epidermal T cells with maintained cytokine production in the elderly participants.