CD11a/LFA-1
CD11a, the alpha chain of LFA-1, pairs with integrin beta 2 (CD18) to form the leukocyte integrin alphaLbeta2, the dominant adhesion receptor mediating firm arrest of leukocytes on vascular endothelium. Its extracellular region contains a ligand-binding I (inserted) domain with an MIDAS motif that engages ICAM-1 and ICAM-2, and the receptor switches from bent low-affinity to extended high-affinity conformations upon inside-out activation. CD11a is expressed on virtually all leukocytes and is essential for T cell transmigration, immunological synapse formation, and cytotoxic function. The anti-CD11a antibody efalizumab was once approved for psoriasis, illustrating its drug-development relevance. Recombinant CD11a/LFA-1 is used in adhesion assays and integrin activation studies.
