IL33 and parasitic infectious disease: Further complicating the matter, another group found that IL-33 was not upregulated in the brain following PbA infection and that IL-33−/− showed a similar survival and parasitemia to wild-type mice; though IL-33 was found to be decreased in the liver and increased in both the lungs and spleen in wild-type mice after infection (Shibui et al., 2016).