Abstract

Purpose: The pathology and mechanisms underlying allergic conjunctivitis are still poorly understood. A few studies have investigated cytokines involvement during allergic conjunctivitis. Severe mouse model that represent the pathology of ocular allergy in human is needed in order to study more extensively the mechanisms underlying allergic conjunctivitis. Here, we have used a mouse model of severe ocular allergy to investigate different cells and cytokines involvement in ocular allergy.

Methods: C57Bl/6 mice were immunized via intraperitoneal injection with ovalbumin in aluminium hydroxide and pertussis toxin and left for 21 days. Immunized mice were then challenged once daily for 7 days with topical ovalbumin (OVA) and were sacrificed a few hours after the last topical OVA administration. Samples were collected from each mouse (of both ocular allergy induced versus normal C57Bl/6) for the whole eye for H&E staining and immunofluoresence staining of different cell types. Cells were explanted from conjunctiva for FACS analysis of different cell types that are present in the conjunctiva. Lymph nodes were also collected for single cell analysis on the presence of different T cell subsets by intracellular cytokine staining.

Results: There is increased in the number of infiltrating cells in the conjunctiva after 7 days challenged with OVA as compared to normal conjunctiva. Double immunfluorescnce staining has confirmed that some of these infiltrating cells consist of mast cells, Th2 and Th9 cells. Further evaluation on the different cells and cytokines that are present in the conjunctiva in severe ocular allergy by intracellular staining has found that the number of cells that secretes IL-9 and IL-10 has increased to almost double during disease but these cytokines did not mainly secreted by Th9 cells as there are no difference in the level of IL-9⁺IL-10⁺ cells. This is different in the lymph nodes where level of Th9 cells increased five-folds during disease suggesting that these cells is present in the systemic but did not migrate to the conjunctiva and contribute to the disease severity.

Conclusions: Different cell types are involved in the pathogenesis of allergic conjunctivitis. IL-9 and IL-10 might contribute to the disease severity in the eye and other cells, but not Th9 cells as the source of IL-9 during allergic conjunctivitis.