T17 cells mediate inflammation in a novel model of spontaneous experimental autoimmune lacrimal keratoconjunctivitis with neural damage.

BACKGROUND

Dry eye disease (DED) affects one third of the population worldwide. In prior studies, experimental autoimmune lacrimal keratoconjunctivitis (EALK) induced by desiccating stress in mice has been used as a model of DED. This model is complicated by a requirement for exogenous epithelial cell injury and administration of anticholinergic agents with broad immunologic effects.

OBJECTIVE

We sought to develop a novel mouse model of EALK and to demonstrate the responsible pathogenic mechanisms.

METHODS

CD4CD45RB naive T cells with and without CD4CD45RB regulatory T cells were adoptively transferred to C57BL/10 recombination-activating gene 2 (Rag2) mice. The eyes, draining lymph nodes, lacrimal glands, and surrounding tissues of mice with and without spontaneous keratoconjunctivitis were evaluated for histopathologic changes, cellular infiltration, and cytokine production in tissues and isolated cells. Furthermore, the integrity of the corneal nerves was evaluated using whole-tissue immunofluorescence imaging. Gene-deficient naive T cells or RAG2-deficient hosts were evaluated to assess the roles of IFN-γ, IL-17A, and IL-23 in disease pathogenesis. Finally, cytokine levels were determined in the tears of patients with DED.

RESULTS

EALK developed spontaneously in C57BL/10 Rag2 mice after adoptive transfer of CD4CD45RB naive T cells and was characterized by infiltration of CD4 T cells, macrophages, and neutrophils. In addition to lacrimal keratoconjunctivitis, mice had damage to the corneal nerve, which connects components of the lacrimal functional unit. Pathogenic T-cell differentiation was dependent on IL-23p40 and controlled by cotransferred CD4CD45RB regulatory T cells. T17 rather than T1 CD4 cells were primarily responsible for EALK, even though levels of both IL-17 and IFN-γ were increased in inflammatory tissues, likely because of their ability to drive expression of CXC chemokines within the cornea and the subsequent influx of myeloid cells. Consistent with the findings of this model, the tears of patients with DED had increased levels of inflammatory cytokines, including IL-17A and TNF-α.

CONCLUSION

We describe a novel model of spontaneous EALK that supports a role for T17 cells in disease pathogenesis and that will contribute to our understanding of autoimmune lacrimal keratoconjunctivitis in many human eye diseases, including DED.