Control of Islet Intercellular Adhesion Molecule-1 Expression by Interferon-α and Hypoxia

The ability of interferon-α (IFN-α) to induce the adhesion molecules that characterize the islets of patients with type I diabetes has been investigated. We have found that all tested recombinant IFN-as will induce major histocompatibility complex (MHC) class I on arterial endothelial cells. Some but not all IFN-as will induce intercellular adhesion molecule-1 (ICAM-1). However, there is only a transient and modest increase in VCAM on arterial endothelial cells. IFN-α has very little effect on endothelial MHC class II expression but will induce these proteins on monocytes. Thus, there is a close concordance between the biological actions of IFN-α and the appearance of those adhesion molecules induced in the islets of patients with type I diabetes. IFN-α is also produced in normal human islets during short-term cultures, probably as a result of the ischemia present at the center of the islet. This induction of IFN-α by hypoxia may explain the previously reported spontaneous induction of ICAM-1 in human islets and may also be a contributing factor to the failure of islet grafts.