Lymphocyte function-associated antigen 1–Intercellular adhesion molecule 1 (LFA-1–ICAM-1) complex (LFA-1–ICAM-1)

The LFA-1–ICAM-1 adhesion interface is a critical protein-protein interaction between Lymphocyte Function-associated Antigen-1 (LFA-1, an integrin) and Intercellular Adhesion Molecule-1 (ICAM-1) (Dustin, 2014, PMID: 24507506). This interaction is fundamental to the formation of the immunological synapse during the engagement between Cytotoxic T Lymphocytes (CTLs) and their target cells, providing the mechanical stability necessary for T-cell receptor (TCR) scanning and the directed release of cytotoxic granules (Springer, 1990, PMID: 1970645). LFA-1, expressed on the surface of leukocytes, undergoes a conformational change from a low-affinity to a high-affinity state upon TCR signaling (inside-out signaling), allowing it to bind ICAM-1 on target cells or vascular endothelium. In pathological contexts, overactivity of this pathway contributes to chronic inflammation and autoimmune disorders by promoting excessive leukocyte infiltration and activation in tissues. Therapeutic targeting of this interface, such as with the small molecule lifitegrast for dry eye disease (Zhong et al., 2018, PMID: 29454638) or the monoclonal antibody efalizumab for psoriasis, aims to disrupt these adhesive contacts to modulate immune responses. However, systemic inhibition carries risks of significant immunosuppression and opportunistic infections, as evidenced by the withdrawal of efalizumab due to cases of progressive multifocal leukoencephalopathy (Major, 2010, PMID: 20037110).

Other names

LFA-1/ICAM-1 interactionIntegrin alpha-L beta-2/ICAM-1 complexCD11a/CD18–CD54 interactionCTL–target cell adhesion interface

Competitive or allosteric inhibition of the LFA-1 I-domain to prevent its interaction with the first immunoglobulin-like domain (D1) of ICAM-1, thereby blocking leukocyte adhesion and the formation of the immunological synapse.