Finally, we show that WSX-1 regulates Th1 cell terminal differentiation during malaria infection through IL-10 and Foxp3 independent mechanisms; the kinetics and magnitude of the Th1 response, and the degree of Th1 cell terminal differentiation, were comparable in WT, IL-10R1−/− and IL-10−/− mice and the numbers and phenotype of Foxp3+ cells were largely unaltered in WSX-1−/− mice during infection. Here, IL10 is linked to infection.