ABSTRACT
The characterization of tight junctions (TJs) has primarily been the province of morphologists and physiologists since their initial recognition as distinct intercellular bridges between epithelial cells (Cereijido, 1991). Scientists in these fields have described the localization, physical appearance, and morphological and functional diversity of TJs in exquisite detail and have determined how these structures interact with and complement other intercellular junctions
in vivo
and in cultured epithelial cell monolayers. Furthermore, these studies have yielded a comprehensive overview of the armamentarium of extracellular barriers available to multicellular organisms for excluding unwanted solutes from the environment while maintaining open endocytic and exocytic pathways for the organism to import nutrients and export metabolic waste.
