Negligible lung CD4+ T cell expression of the regulatory cytokine IL-10 was observed, and there was no lung expansion of regulatory T cells (Tregs) at this pre-patent timepoint18 (Fig. 3D, Supplementary Fig. 11B), implicating a mixed Th2/Th1 responses as the hallmark of pre-patent infection in mice infected with either 40 or 180 cercariae. Here, IL10 is linked to infection.