A schematic presentation of non-polarised and polarized intestinal cell epithelial cells under non-infective conditions or during infection with C. jejuni . (A) Cultured non-polarised intestinal epithelial cells such as INT-407 do not express typical cell-to cell junctions. Thus, basolateral receptors such as focal adhesion structures are accessible and not protected by tight or adherens junctions. (B) Polarised intestinal epithelial cells such as mucin-producing HT29-MTX-E12 cells express the different types of intercellular junctions including the tight junctions (orange), adherens junctions (light blue), focal adhesions (dark blue) and hemidesmosomes (green) which exhibit specific localization in the lateral or basal membranes as indicated. GAP junctions and desmosomes are other examples which are not discussed in this review article. (C,D) C. jejuni is able to infect both cell variants in vitro. This pathogen encodes numerous described pathogenicity-associated factors involved in important processes including bacterial adhesion to, transmigration across, invasion into and intracellular survival within intestinal epithelial cells. For more details see text.