Upregulation of eosinophil adhesion to conjunctival epithelial cells by allergic tears is inhibited by treatment with olopatadine

The mechanism by which eosinophils adhere to the ocular surface during allergic inflammation is unknown. This study examined whether tears from allergic subjects upregulate the ability of human conjunctival epithelial cells (HCE) to promote eosinophil adhesion and the effect of the anti-allergic drug olopatadine on this process. Allergic subjects were treated for 48 hrs with olopatadine in one eye. Tears were collected 24 hrs prior to allergen challenge (both eyes) and 30 min and 90 min post-challenge. HCE were pre-incubated with tears (diluted 1:125 in media) or controls (TNFα, IFNγ) for 24 hrs after which peripheral blood eosinophil adhesion to HCE was measured using an eosinophil peroxidase assay. Blocking antibodies to β2 integrins on eosinophils (A-β2), and ICAM-1 on HCE (A-ICAM-1), examined integrin specificity. Both pre and post-challenge tears activated HCE resulting in upregulated eosinophil adhesion (equivalent to levels of adhesion to TNFα, IFNγ stimulated HCE). Olopatadine treatment completely inhibited the ability of both pre and post-challenge tears to upregulate eosinophil adhesion (equivalent to levels of adhesion to unstimulated HCE). Blocking antibodies demonstrated that eosinophil adhesion to conjunctival epithelial cells in vitro was mediated by β2 integrins on eosinophils (completely inhibited by A-β2) but not via ICAM-1 on HCE (not inhibited by A-ICAM-1). Olopatadine treatment inhibits the pro-inflammatory effect of allergic tears on eosinophil adhesion to HCE in vitro. In vivo, an effect of this magnitude (3–6×10 2 less eosinophils/cm 2) could result in a significant decrease in the numbers of eosinophils maintained on the ocular surface in allergic inflammation.