IL4 and infection: When C57BL/6 IFNAR1−/− were infected with L. major, the clinical course of infection (Figure 2A), the parasite burden (Figure 2B), the cytokine mRNA expression pattern (IFN-γ, IL-12p35, IL-12p40, IL-4, and IL-13) at the site of infection and in the dLN, and the ability to mount a strong and persistent iNOS response along with a transient upregulation of arginase 1 (Figure 3, solid squares vs. open triangles) were indistinguishable in C57BL/6 WT and IFNAR1−/− mice.