An ocular commensal protects against corneal infection by driving an Interleukin 17 response from mucosal γδ T cells

Summary

Mucosal sites such as the intestine, oral cavity, nasopharynx, and vagina all have associated commensal flora. The surface of the eye is also a mucosal site, but proof of a living, resident ocular microbiome remains elusive. Here, we used a mouse model of ocular surface disease to reveal that commensals were present in the ocular mucosa and had functional immunological consequences. We isolated one such candidate commensal, Corynebacterium mastitidis and showed that this organism elicited a commensal-specific interleukin 17 response from γδ T cells in the ocular mucosa that was central to local immunity. The commensal-specfic response drove neutrophil recruitment and the release of antimicrobials into the tears, and protected the eye from pathogenic Candida albicans or Pseudomonas aeruginosa infection. Our findings provide direct evidence that a resident commensal microbiome exists on the ocular surface and identify the cellular mechanisms underlying its effects on ocular immune homeostasis and host defense.

Graphical abstract

Although the eye is a mucosal site, there has been a long-standing controversy regarding whether a resident microbiome exists on the ocular surface. St. Leger et al. show that a microorganism that lives on the conjunctiva tunes local mucosal immunity and protects the eye from pathogenic infection.