In another study, depletion of gut commensals resulted in decreased levels of immune effectors in the tear film and a weakened ocular surface barrier making it more susceptible to Pseudomonas aeruginosa–induced keratitis; mono-colonization of germ-free mice with a specific species, Bacteroides acidifaciens, restored ocular surface secretory IgA levels (48). Here, CD79A is linked to keratitis.