Gut epithelial cells and the host immune system recognize curli fibers.

<p><i>Salmonella</i> and <i>E. coli</i> are intestinal-dwelling bacteria whose curli fibers are recognized by host epithelial cells. The TLR1/2 heterocomplex recognizes the mature curli fiber and causes a signaling cascade in host cells. Recognition of curli results in an increase in PI3K in gut epithelial cells and increases gut epithelial cell barrier formation. Curliated <i>Salmonella</i> elicit an increase in cytokine production by T cells and dendritic cells. <i>Salmonella</i> curli mutants cause decreased epithelial cell barrier formation and lead to increased extraintestinal titers of <i>Salmonella</i>.