IL4 and colitis: In parasite-associated colitis involving Th2-type T cells, cytokines such as IL-4 and IL-13 promote smooth muscle contraction by activating the STAT6 pathway on the one hand, and on the other hand, mast cells are recruited by IL-4, and mast cell degranulation further induces neuronal hyperresponsiveness thereby promoting intestinal smooth muscle contraction and ultimately intestinal parasite expulsion.