IL4 and infection: To investigate how IL-33 might interfer with the host immune response, we measured the levels of the key Th1 cytokines (IFN-γ, IL-12 and TNF-α), key Th2 cytokines (IL-4, IL-5 and IL-13), and the regulatory cytokine IL-10 in the serum at various time-points after infection with PbA.