The tight junction (TJ) is a dynamic, multifunctional complex which, together with adherens junctions and desmosomes, maintains the integrity of the epithelial cell layer(s) that protects multicellular organisms. TJ is located at the apical-most portion of the intercellular junction. It separates the apical and basolateral compartments of epithelia (preventing the lateral diffusion of lipids and proteins between the apical and basolateral domains of plasma membrane) and plays a key role in limiting paracellular permeability to ions and solutes in a charge and size selective manner. TJs appear as multiple strands of fibrils forming a continuous circumferential seal around cells.
