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Abstract
There is growing evidence that cellular adhesion mechanisms characterized by cell-cell and cell-matrix interactions are a fundamental process in the immunobiology of the cornea. Interactions with various extracellular matrix components are mediated by the very late activation (VLA) subgroup of the integrin superfamily of adhesion molecules. The six different VLA dimers known thus far consist of a common beta 1 subunit and a variable alpha (1 to 6) subunit. They serve as receptors for laminin (alpha 3 and alpha 6), collagen (alpha 2 and alpha 3), and fibronectin (alpha 4 and alpha 5). Using in situ immunohistochemistry and monoclonal antibodies, the distribution of the common beta 1 and the variable alpha-chains of VLA molecules was studied in normal human cornea and in cases with scarring or subepithelial/retrocorneal fibrous tissue. Epithelial cells were VLA-beta 1 and VLA-alpha 2, -alpha 3, -alpha 4, -alpha 5, and -alpha 6 positive. This is consistent with their intercellular adhesion and may aid in their attachment to the basement membrane which is composed of collagen, laminin, and fibronectin. Keratocytes in normal stroma expressed only the common beta 1-chain and no detectable alpha-chains. In regions of scar or fibrous tissue, however, an upregulated expression of the alpha-chains was detected. The VLA- alpha 1, -alpha 3, -alpha 4, and -alpha 5 were expressed in young fibrous tissue; in older lesions, VLA- alpha 1, -alpha 2, -alpha 3, -alpha 4, and -alpha 5 could be detected. The corneal endothelium showed a strikingly strong positivity for all VLA integrins.(ABSTRACT TRUNCATED AT 250 WORDS)