IL-22 not only influenced the expression of IL-18 messenger RNA (mRNA) in IECs after infection with Toxoplasma gondii or Citrobacter rodentium infection, but was found to promote a homeostatic production of active IL-18 in the ileum (54), which not only is crucial for host defense but also contributes to inflammation, while assisting in microbial clearance. The gene discussed is IL18; the disease is infection.