EC cells play a functional role in C. rodentium pathogenesis as serotonin has been shown to repress C. rodentium virulence in vivo (36), and we have previously shown CHGA/CHGB to be weakly upregulated during early infection (20), when C. rodentium adapts to the host environment and turns on virulence gene expression. The gene discussed is CHGA; the disease is infection.