In vitro studies characterizing the colonic epithelial cell response to invasive S. flexneri infection using microarrays revealed a strong upregulation of genes encoding chemokines (IL-8, CCL20, CXCL1 and 2), cytokines (GM-CSF and TNF-α) and adherence molecules (ICAM-1) [26] that together likely induce the strong recruitment of PMNs, NK cells, lymphocytes and dendritic cells that is observed during the natural infection of the human colon. Here, TNF is linked to infection.