Expression of the interleukin 1 receptor antagonist in the normal human cornea

The human cornea has been shown to express a number of inflammatory cytokines including IL-1, IL-6 and IL-8. In view of the potent proinflammatory activities of interleukin-1 (IL-1), regulatory mechanisms should be present in the human cornea to control IL-1 mediated inflammatory and immune responses. This is important for the maintenance of the integrity and transparency of the cornea. To test this hypothesis, the authors determined the presence of IL-1 receptor antagonist (IL-tra) in the normal human cornea using an enzyme-linked immunosorbent assay (ELISA). IL-tra is a natural antagonist of IL-1 and competes with IL-1 for the binding to its receptors thereby blocking the inflammatory response. Corneas were either tested immediately or after a 24-hour culture period. Furthermore, the authors separately analyzed the three layers of the cornea. Their results present evidence for the constitutive expression of the IL-tra protein in the normal human cornea and show that both epithelial and stromal cells produce IL-1ra. The epithelial cells are the major source of corneal IL-1ra immunoreactivity, and secrete IL-1ra during culture. Stromal cells contain detectable, albeit low amounts of cell associated IL-1ra. No IL-1ra was detected in the endothelial cell layer. A more accurate understanding of the balance between IL-1 and IL-1ra in ocular tissues and the role of the IL-1ra under physiologie and pathophysiologic conditions will be necessary for an eventual use of IL-1 receptor antagonist as a therapeutical tool.