STAT6 and infection: Under the circumstance of TcpC-secreting UPEC infection, TcpC down-regulates ERK and p38/NF-κB and up-regulates the Akt/STAT6 signaling pathway, respectively, to inhibit M1 but promote M2 macrophage polarization, hereby favoring UPEC to escape from the macrophage-mediated inflammatory anti-infection response.