Tissue origin and virus specificity shape human CD8

CD8+ T cells are classically defined by cytotoxic activity, but it has remained unclear whether cytotoxic programs are compartmentalized across tissues and memory subsets. Here, we established a human organ donor cohort and found that expression of conventional cytotoxic molecules-granulysin, perforin, and granzyme B-was most prominent among circulating memory CD8+ T cells and decreased progressively with tissue residency, inversely mirroring the expression of CD69 and CD103. Other cytotoxic molecules, including granzymes A, H, K, and M, were variably expressed across tissues, and memory CD8+ T cells targeting persistent viruses expressed multiple granzymes coordinately. In an in vitro tonsil system, transforming growth factor-β induced discordant regulation of cytotoxic molecules and CD103. Combined with interleukin-15, this circuitry modulated proliferation and the acquisition of redirected killing activity via perforin and granzyme B. Our findings suggest that human memory CD8+ T cell cytotoxicity is intricately regulated by environmental cues reflecting tissue location and antigen specificity.