Hyperexpression of the High-Affinity IgE Receptor-β Chain in Chronic Allergic Keratoconjunctivitis

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Abstract
Purpose. Although the existence of FcεRI-αβγ2 and FcεRI-αγ2 receptor subtypes was reported, there has been no direct evidence of these two subtypes of FcεRI in vivo. To investigate the existence of these two subtypes of FcεRI in vivo, the authors evaluated the expression of FcεRI-β in the giant papillae of chronic allergic conjunctivitis and compared the expression level of FcεRI-β with control conjunctivae using the anti–human FcεRI-β antibody. methods. FcεRI-β expression in giant papillae obtained from patients with atopic keratoconjunctivitis and vernal keratoconjunctivitis in control conjunctivae was evaluated by immunohistochemistry using anti–FcεRI-β, -α, -γ, and anti–human mast cell tryptase, anti–chymase, anti–basophil, and anti–CD1a antibodies. results. Statistical analyses revealed that the densities of FcεRI-β+ cells, FcεRI-α+ cells, tryptase+ cells, and FcεRI-β+/tryptase+ cells were significantly increased in giant papillae compared with controls. There were two types of FcεRI (αβγ2 and αγ2) on the mast cells of the giant papillae. The ratio of the FcεRI-β+ cell number/FcεRI-α+ cell number in the giant papillae (0.69 ± 0.08 [mean ± SD]) was significantly higher than that of the controls (0.07 ± 0.16). FcεRI-β/tryptase double immunostaining revealed that 81% ± 13% of tryptase+ cells expressed FcεRI-β. FcεRI-β+ cells were preferentially localized within and around epithelial tissue. The authors also found that FcεRI-β was expressed by basophils but not by FcεRI-αγ2–positive Langerhans cells in the giant papillae samples. conclusions. Preferential FcεRI-β expression observed in the mast cells and basophils of giant papillae suggests important roles of FcεRI-β in the pathophysiology of atopic keratoconjunctivitis and vernal keratoconjunctivitis.

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