Roles of OX40 in the Development of Murine Experimental Allergic Conjunctivitis: Exacerbation and Attenuation by Stimulation and Blocking of OX40

PURPOSE. To investigate the roles of interaction between OX40 and OX40 ligand (OX40L) in the development of experimental allergic conjunctivitis (EC) in mice. METHODS. BALB/c mice actively immunized with short ragweed pollen (RW) were intraperitoneally injected on days 0, 2, 4, 6, and 8 with agonistic anti-OX40 Ab, blocking anti-OX40L Ab, or normal rat (nr)IgG. On day 10, the mice were challenged with RW in eye drops, and 24 hours later their conjunctivas, spleens, and blood were harvested for analyses. For examination of the effects of the Abs during the late induction (or effector) phase, actively immunized mice were treated with the Abs just before or at the same time as the challenge. In addition, splenocytes from RW-primed mice were transferred into syngeneic naive mice, and the recipients were treated with Abs twice (on days 2 and 4). On day 4, the mice were challenged with RW and evaluated. RESULTS. When the treatments were performed during the induction phase, anti-OX40 Ab treatment significantly increased clinical EC and eosinophil infiltration into the conjunctiva, whereas anti-OX40L Ab treatment significantly reduced eosinophil infiltration. Compared with splenocytes from nrIgG-treated mice, splenocytes from anti-OX40 Ab-treated mice proliferated vigorously against RW and produced significantly higher amounts of IL-2, -4, and -5 by RW stimulation but a significantly lesser amount of IFN-γ after Con A stimulation. In contrast, splenocytes from anti-OX40L Ab-treated mice produced significantly less IL-5 with RW stimulation and IL-2 and IL-5 with Con A stimulation, whereas significantly more IFN-γ was induced by Con A stimulation. Treatment with anti-OX40 and anti-OX40L Abs during the late induction or effector phase of EC did not affect eosinophil infiltration. CONCLUSIONS. Blocking of the interaction between OX40 and OX40L in vivo inhibits the development of EC. In contrast, forced stimulation of OX40 in vivo significantly exacerbates EC by activating T cells, especially Th2 cells. These effects were noted only in the induction phase of EC, suggesting that the interaction between OX40 and OX40L is important in the generation of Th2 immune responses in the development of EC.