Granzyme K CD8⁺ T cells with tissue-resident features promote intestinal inflammation in patients with Crohn's disease.

The role of CD8+ T cells in Crohn's disease (CD) pathogenesis remains incompletely understood. This study aimed to characterize CD8+ T cells in CD and elucidate their potential contribution to intestinal inflammation. T cells from blood and intestinal tissues of 15 patients with CD were analyzed using single-cell RNA and T cell receptor sequencing. Spatial transcriptomics was conducted on inflamed intestinal tissues from two patients. Analysis of 41,699 CD8+ T cells identified distinct subsets characterized by differential granzyme expression: granzyme B (GZMB+) CD8+ T cells, predominantly in blood with high cytotoxic potential, and granzyme K (GZMK+) CD8+ T cells, enriched in intestinal tissue with lower cytotoxic potential. In the small intestine, GZMK+CD8+ T cells displayed enhanced tissue residency signatures (for example, CXCR6) and downregulated egress-related genes (S1PR1and S1PR5). GZMK+CD8+ T cells displayed robust interactions with myeloid cells via the CXCR3-CXCL9/10 axis, coupled with notable colocalization in the small intestine. Pharmacological inhibition of GZMK alleviated intestinal inflammation and tissue damage in a murine model of intestinal injury, supporting its role in modulating inflammatory responses. Together, these findings highlight GZMK as a potential modulator of intestinal inflammation and a candidate for further therapeutic investigation.