Rolling interactions of leucocytes are mediated by a family of proteins called as selectins 3 types of selectins: L - selectins ( on leucocytes ) , E - selectin ( on endothelium ), P-selectin ( On platelets, endothelium ) Integrins: Firm adhesion of leucocyte to endothelial cell is mediated by family of leucocyte surface proteins called as integrins Transferrin: Iron transpoing protein PECAM-1: (platelet endothelium cell adhesion molecule): Present in the inter-cellular junction between endothelial cells Help in migration of leucocytes