[Adhesion molecules and asthma]

The inflammation markers in asthma can help the prognosis, diagnosis and monitoring of the respiratory illness. The adhesion molecules (AM) are membrane glycoproteins that intervene in the contact between the two cells or between the cell and the extracellular matrix. Their aim is to maintain the contact between two cells for the time that is necessary in order to establish a communication between them and so that the function indicated takes place. The most important functions of the AM's are to facilitate the adhesion of the circulating leukocytes to the vascular endothelium with the posterior transendothelial migration that contribute, by doing so, to the perpetuation of the inflammatory reaction in bronchial asthma. The AM's can act as receptors or as specific ligands for these receptors and are expressed both in leukocytes and endothelial cells as well as in epithelial cells. There are several AM families that allow for these interactions and that collaborate in the specificity of the cellular recognition in the immunologic reaction. The most known are the selectines, the super family of the immunoglobulins and the integrins, that act in a cascading manner. In bronchial asthma, the inflammatory reaction consists of three sequential processes: the recognition-activation phase, the inflammation phase and the solution phase. The AM's act in the second or the inflammation phase. The positive control of the E-selectine, followed by that of the ICAM-1 on the surface of the endothelium cell, leads in sequence to the adhesion, initially of the neutrophils and then the lymphocytes and monocytes, as a response to the antigenic stimulus. The initial loose adhesion of the leukocytes to the vascular endothelium, activated by contact or by cytokines, takes place by means of the selectines. In the microvasculature the strength of the flow pushes the adhered leukocytes, causing the disappearance of the selectine-ligand interactions which form againg quickly in descending direction as the leukocyte moves. The result is the rolling of the spherical leukocyte along the surface of the endothelium. This leukocyte becomes activated and its cytoskeleton is rearranged, and now has a flat shape and the affinity of its integrins is increased by the endothelial ligands. This leukocyte can die within a few days, can activate itself or exit via the lymphatic vessels. The activated monocytes that are located in the extravascular tissues are differentiated from the histiocytes, which are the final cellular effectors of the inflammatory reaction. The importance of the knowledge of the AM structure and the functions, is due to the fact that there is a possible pharmacological action on them. The data obtained from clinical studies, as well as the in vitro results, confirm the importance of the AM modulation as well as therapeutic approach to bronchial asthma.