LFA-1

LFA-1, lymphocyte function-associated antigen 1, is an integrin adhesion receptor assembled from the CD11a alpha subunit and the CD18 beta subunit. It is a heterodimer, not the name of either chain alone. Binding to intercellular adhesion molecules such as ICAM-1 helps immune cells make regulated contacts with other cells. ^[ref]

The importance of regulation became clear in an experiment linking recognition to adhesion. M. L. Dustin and T. A. Springer cross-linked the T-cell receptor and observed a rapid, transient increase in LFA-1-dependent adhesiveness toward ICAM ligands. A recognition event could therefore alter how strongly the cell attached, rather than adhesion being a permanently fixed property of its surface.^[ref]

An illuminating distinction is receptor abundance versus effective adhesion. Two cells can display similar numbers of LFA-1 molecules yet differ in the strength of contact because receptor state, organization and binding geometry differ. The reported increase in cellular avidity is a combined functional measurement; it should not automatically be read as an identical fold-change in the affinity of every isolated receptor molecule.

LFA-1 and Mac-1 share the CD18 component but use different alpha subunits. Shared machinery can support related adhesion functions without making their ligand recognition or cellular roles interchangeable.