Phagocytosis of particulate antigens by corneal epithelial cells stimulates interleukin-1 secretion and migration of Langerhans cells into the central cornea.

Under normal physiological conditions, the central corneal epithelium is devoid of Ia+ Langerhans cells. However, a variety of stimuli can induce the migration of peripheral Langerhans cells into the central regions of the cornea. In the present study, Langerhans cell migration was induced by the instillation of either sterile latex beads or formalin-killed Staphylococcus aureus into shallow incisions in the central corneal epithelium. Langerhans cells could be detected in the central cornea as early as 24 hours following instillation of either latex beads or S. aureus and remained for at least 6 weeks. Phagocytosis of latex beads by corneal epithelial cells was demonstrated in vivo and in vitro. Moreover, phagocytosis of latex beads stimulated corneal epithelial cells to secrete increased amounts of interleukin-1 (21-83% increase). The centripetal migration of peripheral corneal Langerhans cells in response to phagocytosis of latex beads could be mimicked by injecting as little as 0.001 units of human purified interleukin-1 (IL-1) into the central corneal epithelium. The IL-1 induced chemotaxis could be blocked by coinjection of anti-IL-1 antibody but not irrelevant antibody. The findings indicate that the exclusion of Langerhans cells from the central corneal epithelium is a dynamic process that can be regulated by the resident corneal epithelial cells themselves and raises the possibility that corneal epithelial cells and Langerhans cells collaborate in antigen processing within this organ.