MYD88 and infection: Likewise, SAA1 expression in IEC is regulated by MyD88 in an IEC-intrinsic manner during infection with C. rodentium. SAA1 has direct bactericidal effects on Gram- bacteria such as E. coli [76] and therefore may directly contribute to the host response against C. rodentium. Moreover, it has been demonstrated that attachment of segmented filamentous bacteria to epithelial cells triggers the expression of SAA1 in epithelial cells, leading to the activation of intestinal Th17 cells [48, 77].