108 - Paradoxical Effects of Platelets Aggregation on Thiol Redox Status

Ox40 ligand (Ox40L)–Ox40 pathway has been shown to enhance Th2 responses and play a role in pathogenesis of cutaneous leishmaniasis (CL) caused by Leishmania major. Using Ox40l−/− BALB/c mice we analyzed the role of this pathway in determining the outcome to CL caused by L. mexicana and compared to L. major. Contrary to our expectations, Ox40l−/− mice were highly susceptible to both L. major (LV39) and L. mexicana (M379) and developed large non-healing lesions containing parasites comparable to Ox40l+/+ BALB/c mice. Interestingly, upon in vitro stimulation with Leishmania antigen (LmAg), the lymph node cells from L. major infected Ox40l−/− mice produced significantly less IL-4 and IL-10 compared to Ox40l+/+ mice. L. mexicana infected Ox40l−/− and Ox40l+/+ mice did not show any difference in the production of IL-4 and IL-10. No difference was noted in the amount of Th1 cytokines IFN-ү and IL-12 produced by Ox40l−/− and Ox40l+/+ mice infected with either parasite. These results indicate that the Ox40L–Ox40 pathway promotes Th2 bias only in L. major infection but not L. mexicana infection and this pathway is not critical for susceptibility to CL.