Lymphocyte interaction with endothelium.

In the postcapillary venules selectin-sialomucin interactions mediate “rolling” of lymphocytes on endothelium. Chemokines presented by heparan sulfate proteoglycans on the endothelium can bind to chemokine receptors, which are G protein-coupled 7-membrane-spanning molecules. This leads to activation of members of the integrin family on the surface of lymphocytes. Interaction of integrins with their ligands results in stable adhesion of lymphocytes to endothelium and in diapedesis.