Sjögren-like Lacrimal Keratoconjunctivitis in Germ-Free Mice

Abstract

Purpose : Commensal bacteria play an important role in formation of the immune system, but their role in maintenance of immune homeostasis at the ocular surface and lacrimal gland is incompletely understood. The objective of this study was to explore a potential link between commensal bacteria and ocular surface and lacrimal gland homeostasis.

Methods : Eight-week-old Germ-Free (GF) mice and Specific Pathogen Free (SPF) C57BL/6 mice of both genders were used. Corneal barrier function was assessed by Oregon Green Dextran (OGD) dye staining. Conjunctiva goblet cell (GC) density was investigated by Periodic Acid Schiff staining. Lacrimal gland (LG) infiltrating lymphocytes were characterized by flow cytometry. T-cell-related cytokines were evaluated by quantitative real-time polymerase chain reaction (Q-PCR) in LG lysates. Caspase 3 activity was measured with a commercial kit.

Results : Female GF mice had significantly greater corneal OGD staining compared to the female SPF group (P<0.001). There was no significant difference in OGD staining between male GF and SPF mice. GF mice of both genders had significantly lower GC density than SPF mice (P<0.001). Flow cytometry analysis showed a significant increase in CD4⁺ and CD8⁺ T cells in the female GF LG compared to the SPF LG (P<0.05 for both), but there was no significant difference in B cells. Female GF LG had higher levels of IFN-γ, and IL-1β mRNA expression than female SPF LG from SPF mice (P<0.05 for all). Male GF mice had significantly higher expression of IFN-γ in the LG than SPF male (P<0.05). Significantly increased caspase 3 activity was measured in GF mice compared to SPF mice of both genders (P<0.001 and P<0.01 female and male comparison, respectively); however, higher levels were present in female GF than male GF LG (P<0.01).

Conclusions : Germ-free mice have a spontaneous Sjögren-like lacrimal keratoconjunctivitis demonstrating that commensal bacteria may play a role in maintaining immune homeostasis on the ocular surface and lacrimal gland.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.