FIGURE 1.

Regulatory feedback loop facilitate parasite persistence. (1) Activated T cells both CD4 and CD8 produce IFNγ, which in combination with IL-1β drives IL-27 production by macrophages. (2a) IL-27 inhibits generation of potentially protective Th17 cells and (2b) promotes together with IL-21 the generation IL-10 secreting T cells. (3) IL-10 cause down-regulation of IL-12, MHC class II as well as co-stimulatory molecules on macrophages and render macrophage unresponsive to activation signals such as IFNγ. Together this facilitates parasite replication and disease progression.