Folia Biologica
Journal of Cellular and Molecular Biology, Charles University 

The molecule CD18 is a subunit of leukocyte adhesion molecules belonging to the β2 integrins (CD11/CD18). Recently, free forms of intracytoplasmic CD18 molecules have been described (Drbal et al., 2000). Integrins are polypeptide heterodimers consisting of a common 95-KD β chain (CD18) non-covalently linked to a unique α subunit: 180-kD αL (CD11a), 170-kD αM (CD11b), or 150-kD αX (CD11c). The molecule CD11a/CD18 (LFA-1) is primarily expressed on lymphocytes, CD11b/CD18 (MAC-1) on neutrophils and monocytes, CD11c/CD18 on monocytes and macrophages (Gahmberg et al., 1997). The integrins are type I membrane proteins containing an N-glycosidic carbohydrate (Asada et al., 1991). The extracellular domains of integrins mediate cell-matrix and cell-cell contacts, while their cytoplasmic tails associate with the cytoskeleton. Integrins are not active in resting cells, but need activation to become adhesive. The CD18 molecule has been shown to play a central role in regulating activity (Green et al., 1998). The β2 integrins bind to intercellular adhesion molecules ICAM and to several soluble proteins, many of which are involved in inflammation (Gahmberg et al., 1998). Their pivotal importance is best evident in individuals lacking functional CD11/CD18 due to mutation in the CD18 gene with LAD (leukocyte adhesion deficiency) syndrome in man (Arnaut, 1990) or BLAD (bovine leukocyte adhesion deficiency) syndrome in cattle (Kehrli et al. 1990; Shuster et al., 1992). This syndrome is characterized by repeated infections.

« Previous article