Signalling and adhesive properties of the integrin leucocyte function-associated antigen 1 (LFA-1).

Leucocyte function-associated antigen 1 (LFA-1; also known as CDlldCD18) belongs to the family of integrins which is one of the most important families of cell adhesion molecules and includes receptors that bind to the extracellular matrix as well as receptors involved in cell-cell interactions. Recent findings have demonstrated that integrins are both adhesion receptors and signalling molecules. LFA-1 plays a crucial role in many cellular processes (migration, antigen presentation, cytotoxicity, cell proliferation, haemopoiesis) by mediating cell-cell adhesion by binding to ligands such as intercellular adhesion molecules 1, 2 and 3 (ICAM-1, -2 and -3) [l]. All integrins are aP heterodimers, with the a-subunit non-covalently associated with a P-subunit [2]. Integrins can be grouped into subfamilies according to a common P-subunit [3]. Leucocytes express PI (VLAs), a2 (LeuCAMS, CD11/CD18) and 8, (homing) integrins. LFA-1 belongs to the subfamily of Pz integrins, which includes Mac-1 ( a J 2 ; CD1 lb/CD18), p150,95 (a&; CDllcKD18) and aD CD 1 1 d C D 18), being exclusively expressed by leucocytes [4,5].