IL-10 is not required for the alleviation of collagen-induced arthritis by non-lethal malarial infection in mice

We previously reported that Plasmodium yoelii 17XNL (Py), a non-lethal rodent malarial parasite, could suppress collagen-induced arthritis (CIA) and increase the production of T cell-derived interleukin (IL)-10. However, it remained unclear whether IL-10 is essential for the Py-induced suppression of CIA. Male IL-10 knockout (KO) DBA/1 J mice were immunized with bovine type II collagen (CII) and subsequently infected with Py at one week post-immunization. The development of arthritis was evaluated by an arthritis score up to 6 weeks post-immunization. At 3 weeks post-immunization, cytokine production from splenocytes and serum anti-CII IgG/IgG1/IgG2a levels were compared between non-infected control mice and Py-infected mice. Py infection inhibited the development of CIA in IL-10KO mice until 4 weeks post-immunization, after which the arthritis score reached levels comparable with the control mice. Both pro-arthritic (IL-17 and TNF-α) and anti-arthritic (IFN-γ and IL-4) cytokines were down-regulated during the periods of parasitemia, while no significant differences were observed in levels of anti-CII IgG antibodies. Our findings indicate that Py alleviates CIA via IL-10-independent mechanisms.