Objective: To characterize the expression and regulation of conjunctival mast cell surface receptors important in allergic inflammation.
Methods: Mast cells were isolated from human conjunctival tissues of cadavers. Mast cell surface markers were identified using flow cytometry with antibodies to IgE, Fc epsilonRI, c-kit, and intercellular adhesion molecule-1 (ICAM-1). We evaluated the effect of 24-hour tumor necrosis factor alpha (TNF-alpha) or interleukin 4 (IL-4) incubation on the expression of mast cell c-kit, ICAM-1, and surface-bound IgE.
Results: Staining of mast cells (c-kit and/or tryptase positive) yielded positive results for all of the variables measured. The intensity of mast cell c-kit staining increased with TNF-alpha incubation, but decreased below that of unstimulated mast cells when incubated with IL-4. Anti-ICAM-1 and anti-IgE staining were increased over that of unstimulated cells when incubated with TNF-alpha or IL-4.
Conclusions: In this model, TNF-alpha up-regulates mast cell surface receptors and cell-bound IgE. Interleukin 4 up-regulates mast cell ICAM-1 and cell-bound IgE, but down-regulates c-kit.
Clinical relevance: Conjunctival mast cells play a critical role in the pathogenesis of atopic ocular disease. Characterization of the expression and regulation of mast cell surface receptors is important to the development of potential novel treatments for ocular inflammation.