Key roles of LFA-1 in leukocyte migration and immune response

To patrol the body effectively for infectious organisms, the cells of the immune system must both circulate as nonadherent cells in the blood and lymph and, in the presence of a foreign antigen, be able to congregate in lymphoid organs, cross endothelial and basement membranes to aggregate at sites of infection, and adhere to cells bearing foreign antigen. In this context, lymphocyte function-associated antigen-1 (LFA-1, α_Lβ₂, CD11a/CD18) plays a critical role (1) in forming stable bonds with counter receptors in the vascular walls to allow leukocytes to leave the circulation and (2) in validating the interaction between an antigen presenting cell and a T lymphocyte. Both roles are described in detail in this review.