LFA-1

(= CD11a/CD18; lymphocyte function-related antigen-1)

Heterodimeric lymphocyte plasma-membrane protein ( aL 180 kD, b 95 kD) that binds ICAM-1, particularly involved in cytotoxic T-cell killing. One of the integrin superfamily of adhesion molecules. Deficiency of LFA-1 in leucocyte adhesion deficiency (LAD) syndrome leads to severe impairment of normal defences and poor survival prospects. The related surface adhesion molecules (sometimes referred to as the LFA-1 class of adhesion molecules) are Mac-1 (aM 170 kD, b 95 kD; CD11b/CD18) and p150,95 (aX 150 kD, b 95 kD; CD11c/CD18) ; they are also defective in severe forms of LAD because the b subunit, which is apparently common to all three, is missing. Mac-1 (also known as Mo-1 in earlier literature) is the complement C3bi receptor (CR3) and is present on mononuclear phagocytes and on neutrophils; p150,95 is less well characterized, but is particularly abundant on macrophages.