IL18 and mastocytosis: In general, patterns of circulating cytokines over time following P. yoeliiyoelii 17XNL infection showed evidence of dual activation and cross talk between Th1 and Th2 responses, with the earliest increases (day 4 p.i.)in IL-6, IL-18, and interferon-γ (IFN-γ) (Fig. 5A to C) along with IL-4 and IL-10 (Fig. 6A, B), which corresponded to the first peak of intestinal mastocytosis (Fig. 3A).