SMAD4 and cyst: Zhou et al. [17] stimulated mouse spleen cells with hydatid cyst fluid, The increase of SMAD4, the downstream signal transduction protein of TGF-β, suggests that the differentiation of Treg cells and the SMAD4 signal pathway may be involved in the immune escape process of the cyst fluid to the host, which is consistent with the results of this study in vitro.