Exocrine gland-resident memory CD8+ T cells use mechanosensing for tissue surveillance

Tissue-resident CD8(+) T cells (T-RM) continuously scan peptide-MHC (pMHC) complexes in their organ of residence to intercept microbial invaders. Recent data showed that T-RM lodged in exocrine glands scan tissue in the absence of any chemoattractant or adhesion receptor signaling, thus bypassing the requirement for canonical migration-promoting factors. The signals eliciting this noncanonical motility and its relevance for organ surveillance have remained unknown. Using mouse models of viral infections, we report that exocrine gland T-RM autonomously generated front-to-back F-actin flow for locomotion, accompanied by high cortical actomyosin contractility, and leading-edge bleb formation. The distinctive mode of exocrine gland T-RM locomotion was triggered by sensing physical confinement and was closely correlated with nuclear deformation, which acts as a mechanosensor via an arachidonic acid and Ca2+ signaling pathway. By contrast, naive CD8(+) T cells or T-RM surveilling microbe-exposed epithelial barriers did not show mechanosensing capacity. Inhibition of nuclear mechanosensing disrupted exocrine gland T-RM scanning and impaired their ability to intercept target cells. These findings indicate that confinement is sufficient to elicit autonomous T cell surveillance in glands with restricted chemokine expression and constitutes a scanning strategy that complements chemosensing-dependent migration.