Junctional adhesion molecule A（JAM-A）which belongs to the immunoglobulin superfamily, seems to play a role in epithelial tight junction formation.JAM-A is expressed in endothelium, epithelium and leukocytes (at protein level).JAM-A contains Ig-like V-type 1 and Ig-like V-type 2 domains ,the Ig-like V-type 2 domain is necessary and sufficient for interaction with integrin alpha-L/beta-2.