ABSTRACT
This chapter examines the methods employed by pathogens to cross intact skin and mucosae. It shows that the different classes of pathogen, bacteria, fungi, viruses and parasites employ remarkably similar strategies to enter epithelial cells that are the barrier to their invasion of deeper tissue and organs. Pathogens entering the sub-epithelial tissues are engulfed and destroyed by resident phagocytic cells such as macrophages. Transmembrane proteins of tight junctions are the junction components most vulnerable to pathogenic microorganisms when they contact the mucosal epithelium because they are the most apically located. Several pathogenic fungi, including Candida albicans, can traverse epithelial barriers by proteolytic degradation of intercellular tight junctions. Pathogenic bacteria use some methods of actin cytoskeleton reorganisation to induce endocytosis by mucosal epithelial cells. In order to reorganize the actin cytoskeleton to allow the formation of lamellipodia and pseudopodia for their uptake pathogens destabilize microtubules.
