Analysis of human gastric epithelial cell IL-8 response to the H. pylori cag T4SS. H. pylori was grown in culture medium alone or supplemented with either ferric chloride, apo-, or holo-lactoferrin prior to co-culture with human gastric epithelial cells. ELISA analysis of IL-8 secretion (a proxy for cag T4SS activity) revealed that exposure to ferric iron (Fe) or holo-lactoferrin (holo-Lf) repressed the activity of the cag T4SS, whereas bacterial exposure to medium alone (Medium Alone) or apo-lactoferrin (apo-Lf) results in robust IL-8 secretion, indicative of cag T4SS activity. (N=3–5 biological replicates, a,b,c=P<0.05, One-way ANOVA).