Carboxypeptidase A3 expression in intraepithelial mast cells of chronic allergic conjunctivitis

Abstract

Purpose: Carboxypeptidase A3 (CPA3) is a protease known to be expressed in mast cells. Preferential CPA3 expression in intraepithelial mast cells in atopic asthma was reported previously. We investigated the expression of CPA3 in the giant papillae obtained from vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) patients, and compared the expression with known mast cell immunohistochemical markers (tryptase/chymase), and a mast cell activation marker; high affinity IgE receptor β chain (FcεRIβ).

Methods: 10 giant papillae were resected for therapeutic purpose and sections were prepared as previously described. (IOVS.50:2871-2877) Anti-CPA3/anti-tryptase or anti-CPA3/anti-chymase double immnunohistochemical staining was carried out by indirect immunofluorescent method. Anti-CPA3/anti-FcεRIβ double immunohistochemical staining was carried out by direct immunofluorescent method using Zenon labeling system (Invitorogen, CA).

Results: CPA3-tryptase double immunostaining showed that CPA3 positive staining was observed in the intraepithelial and subepithelial tryptase positive mast cells. CPA3-chymase double immunostaining showed both CPA3+ chymase - mast cells and CPA3+ chymase+ mast cells in the conjunctival epithelium of the giant papillae samples. CPA3+ chymase+ mast cells preferentially located at near the epithelial-stromal borders. CPA3/ FcεRIβ double positive cells were also observed the giant papillae samples.

Conclusions: Preferential CPA3 expression in the intraepithelial mast cells of giant papillae was observed. Tryptase positive/Chymase negative (MCT) mast cells are predominant mast cell type for CPA3 expression. CPA3 expression may relate to mast cell activation or maturation.

Keywords: 475 conjunctivitis • 555 immunomodulation/immunoregulation