Sticking to the point

Macrophage inflammatory factor may be one of the adhesion triggers influencing the activity of integrins in promoting the adhesion of leukocytes to the endothelium of postcapillary venules. A consensus model has emerged in which members of the selectin and integrin families are part of a two-step process required for leukocyte extravasation. Selectins promote the transient adhesion of leukocytes to the epithelium by slowing their passage through postcapillary venules. This transient adhesion is then intensified by the action of integrins.