Intercellular Adhesion Molecule-2 (ICAM-2) Expression in the Mouse Eye
Intercellular adhesion molecule-2 (ICAM-2) is an important factor in leukocyte recirculation and trafficking (Nortamo et ai., 1991; Staunton et ai., 1989). Recent studies (Xu et ai., 1996; Hobden et ai., 1999) have suggested that ICAM-2 may function as an intercellular adhesion molecule-l (ICAM-1) surrogate, which recruits polymorphonuclear leukocytes (PMN) during an inflammatory response. The purpose of this study was to identify ICAM-2 expression in the murine eye and to compare it to that of ICAM-1. ICAM-2 and ICAM-1 expression were studied in both an outbred (Swiss) and an inbred strain (129/Sv) of mice. The ICAMs were detected by immunofluorescence (ICAM-1 and ICAM-2) and by an immunohistochemical technique (ICAM-2) on frozen sections of mouse eyes. To study ICAM-2 and ICAM-1 expression during an inflammatory response, mouse eyes were infected with Pseudomonas aeruginosa for 6 hr and then sectioned. ICAM-2 was constitutively expressed on vascular endothelium in the conjunctiva and the anterior iris. It was not upregulated following P. aeruginosa infection. ICAM-1 was expressed on vascular endothelium in the conjunctiva and on several other cell types in the eye constitutively. During infection, ICAM-1 was upregulated and expressed on conjunctival stromal fibroblasts and vascular endothelium, corneal epithelium, corneal stromal keratocytes, and corneal endothelium. Previous reports ofICAM-1 expression in the eye (Figdor et ai., 1992; Foets et ai., 1993;Goldberg et ai., 1994; Hobden et ai., 1999; Vadas et ai., 1992; Vorkauf et a/., 1993) and reports of ICAM-2 expression on vascular endothelium were confirmed (Xu et a/., 1992; Xu et ai., 1996; de Fougerolles et ai., 1991). ICAM-2 and ICAM-1 are both found on vascular endothelium in the eye, supporting the hypothesis that ICAM-2 is an ICAM-1 surrogate.
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