Chemotaxis by various cytokeves of ia⁺ langerhans cells into the central cornea of mice: effect of interleukins 5 and 7

Purpose: Although under normal conditions it is devoid of Ia⁺ Langerhans cells (LC), a variety of stimuli, including several cytokines, have been shown to induce a centripetal migration of LC into the central cornea. Having previously shown Interleukins (IL)-3 and IL-4 to be lacking any such activity, we sought to determine whether IL-5 and IL-7 have such an effect upon these antigen presenting cells and, if so, how these cytokines might interplay in the known aspects of the chemotactic cascade. Methods: BALB/c, C57BL/6 and C3H/HeJ mouse corneas were injected with varying amounts of as much as 25.0 IU recombinant (r) murine (mu) IL-5 or 1.0 × 10⁶ IU r mu IL-7 and 16 hours later evaluated by immunoperoxidase staining. Results: Unstimulated 6-8 week old mouse corneas contain 0-3 (BALB/c: 0.28±0.46; C57BL/6: 0.41±0.59; C3H/HeJ: 0.82±0.75) la⁺ LC peripherally, with none regularly found centrally or paracentrallv). Although intracorneal injection of r mu IL-5 failed to induce the migration of la' LC (0.25±0.46 BALB/c, 0.58±0.79 C57BL/6 and 0.83±0.83 C3H/HeJ), r mu IL-7 induced 29.88±2.42 BALB/c, 28.83±2.21 C57BL/6 and 27.67±2.02 C3H/HeJ Ia⁺ LC. The addition of cyclosporine A (CsA), interferon (DFN)-γ and transforming growth factor (TGF)-β abrogated this chemotactic effect while the addition of rapamycin(RAPA) did not. Thus, r mu IL-5 failed to induce the chemotaxis of a statistically significant number of Ia⁺ LC into the central corneas of the murine strains studied, while r mu IL-7 successfully induced the migration of these immunocompetant cells into the central corneas of these same murine strains (BALB/c: p=0.90; C57BL/6: p=0.99; C3H/HeJ: p=0.92). Conclusions: We propose that IL-7, but not IL-5, is chemotactic for Ia⁺ Langerhans cells.