Epithelial tight junctions.

Epithelial cells differentiate by polarizing into an apical and a basolateral domain and by forming tight junctions (TJ) that control permeation through the paracellular route. The molecular nature of this structure, as well as the processes of assembly, sealing, and regulation, are not yet fully understood. However, the use of epithelial cell lines cultured as monolayers is helping to elucidate the structure and function of this important cellular feature. Furthermore, the development of specific antibodies that interact directly with junctional components may help to solve the molecular structure of the TJ.