IL22 and infection: As seen in Fig 2C, Il22-/- mice exhibited greater pathology than wild-type mice infected with L. major. To determine if the increased pathology observed following L. major infections was due to higher parasite levels in Il22-/- mice, we assessed the parasite burden in wild-type and Il22-/- mice at 2, 5 and 12 weeks of infection, and found no significant differences (Fig 2D).