Lymphocyte function-associated antigen 1, also known as LFA-1 is found on all T-cells and also on B-cells, macrophages, neutrophils and NK cells and is involved in recruitment to the site of infection. It binds to ICAM-1 on antigen-presenting cells and functions as an adhesion molecule. LFA-1 is the first to bind T-cells to antigen-presenting cells and initially binds weakly. A signal from the T-cell receptor and/or the cytokine receptor changes the conformation and prolongs the cell contact, allowing the T-cell to proliferate. LFA-1/ICAM-1 interaction has recently been shown to be important for T cell-T cell interactions, leading to further T cell differentiation.
LFA-1 is part of the family of leukocyte integrins that are recognised by their common β-chains (β2, CD18). LFA-1 also has a distinct α-chain (αL, CD11a).
LFA-1 has also been found in a soluble form.