Adhesion

The leukocyte alongside the endothelial cell then adheres to it by means of a complex interaction between complementary adhesion molecules

• within minutes, released histamine and thrombin stimulate the appearance of a molecule, P-selectin of the endothelial cell surface
• later, interleukin-1 and tumour necrosis factor promote the production of another endothelial molecule, E-selectin
• these molecules retard the movement of the marginating leukocyte but do not halt it completely
  • this can only occur with the expression of a second-wave of binding proteins. On the leukocyte, these are termed integrins. Their complementary molecules on the endothelium are intercellular adhesion molecules - ICAMs - and vascular adhesion molecules - PECAMs
  • co-factors such as calcium are also required.

Disorder within the adhesion molecule structure can lead to a failure of leukocytes to reach the region of inflammation - leukocyte adhesion deficiency(1).

Reference:

• 1) Anderson, D.C., Springer, T.A. (1987). Leukocyte adhesion deficiency. An inherited defect in the Mac-1, LFA-1, p150,95 glycoproteins. Ann. Rev. Med. 38, 175.