SURFACE ATTACHMENT OF SALMONELLA-TYPHIMURIUM TO INTESTINAL EPITHELIA IMPRINTS THE SUBEPITHELIAL MATRIX WITH GRADIENTS CHEMOTACTIC FOR NEUTROPHILS

During intestinal disease induced by Salmonella typhimurium transepith elial migration of neutrophils (PMN) rapidly follows attachment of the bacteria to the epithelial apical membrane. Among the events stimulat ed by these interactions is the release of chemotaxins that guide PMN through the subepithelial matrix and subsequently through the epitheli um itself (McCormick, B. A., S. P. Colgan, C. Delp-Archer, S. I. Mille r, and J. L. Madara. 1993. J. Cell Biol. 123:895-907). Given the subst antial volume flow that normally characterizes matrix compartments und erlying transporting epithelia, it is unclear how such transmatrix sig naling is sustained. Here we show that when underlying matrices are is olated from biophysically confluent polarized monolayers of the human intestinal epithelial cell line T84, they fail to support substantial transmatrix migration of PMN unless an exogenous chemotactic gradient is imposed. In contrast, such matrices isolated from confluent monolay ers apically colonized with S. typhimurium support spontaneous transma trix migration of PMN. Such chemotactic imprinting of under lying matr ices is resistant to volume wash and is paralleled by secretion of the known matrix-binding chemokine IL-8. Chemotactic imprinting of the ma trix underlying S. typhimurium-colonized monolayers is dependent on ep ithelial protein synthesis, is directional implying the existence of a gradient, and is neutralized by antibodies either to IL-8 or to the I L-8 receptor on PMN. An avirulent S. typhimurium strain, PhoP(c), whic h attaches to epithelial cells as efficiently as wild-type S. typhimur ium, fails to induce basolateral secretion of IL-8 and likewise fails to imprint matrices. Together, these observations show that the epithe lial surface can respond to the presence of a luminal pathogen and sub sequently imprint the subepithelial matrix with retained IL-8 gradient s sufficient to resist washout effects of the volume flow that normall y traverses this compartment. Such data further support the notion tha t the primary role for basolateral secretion of IL-8 by the intestinal and likely other epithelia is recruitment of PMN through the matrix t o the subepithelial space, rather than directing the final movement of PMN across the epithelium.