LEUKOCYTE TRAFFICKING IN EXPERIMENTAL AUTOIMMUNE UVEITIS IN-VIVO

Leukocyte trafficking from blood into tissue is a fundamental process in immune surveillance and the immune response to stimuli. Experimenta l autoimmune uveitis (EAU) is an animal model for posterior uveitis an d is mediated by T lymphocytes and macrophages that infiltrate the pos terior segment of the eye. To analyze leukocyte migration into retinal tissue during the course of EAU, labeled cells were identified in viv o by scanning laser ophthalmoscopy and hi retinal flatmounts by confoc al microscopy. Adhesion of blood leukocytes to retinal endothelial cel ls in vivo was significantly raised 48 h before the appearance of clin ical disease, and this correlated with the in creased expression of CD 54 on retinal vessels. Mitogen-activated spleen cells and CD4(+) T cel ls only entered into retinal tissue in animals with clinical disease a nd not naive recipients. The disease status of the donor animal had no effect on leukocyte trafficking. These results, which identify leukoc yte-endothelial cell interactions in vivo, suggest that the activation of the retinal endothelium is a prerequisite to leukocyte adhesion an d extravasation into ocular tissue during EAU.