Leishmania major: Interleukin-13 increases the infection-induced hyperalgesia and the levels of interleukin-1β and interleukin-12 in rats

Interleukin-13 (IL-13) is a powerful anti-inflammatory cytokine that was previously shown to be a susceptibility factor for Leishmania major (L. major) infection. In this study we report a different role for IL-13 in rats infected with L. major; rIL-13 stimulates expression of pro-inflammatory cytokines and IL-12 which is a key cytokine in protective immunity against Leishmania. Infected rats received daily injections of rIL-13 for eight consecutive days which resulted in increased pain perception for the first week post-infection assessed by thermal pain tests. This hyperalgesia was accompanied by a sustained early up-regulation of interleukin-1β followed by an up-regulation of IL-12p70. Real-time PCR showed no negative impact for rIL-13 upon the clearance of the parasites from the infection sites and blood.