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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.

M. L. Dustin is the first author, with T. A. Springer, of a 1989 study testing how antigen recognition regulates T cell cell adhesion. Cross-linking the T-cell receptor rapidly increased the strength of adhesion through LFA-1 to its intercellular binding partners, and the effect was transient.^[ref]

The experiment distinguishes the amount of a surface molecule from its functional state. A cell can change how effectively an existing adhesion system works after receiving a signal, without that observation requiring a newly made adhesion apparatus. The short-lived response also supplies a way to coordinate recognition, stable contact and later detachment.^[ref]

T. A. Springer contributed to experiments connecting immune-cell surface proteins with recognition and cell adhesion. In a 1982 study with D. I. Beller and collaborators, selective antibody blocking related Mac-1 to binding of targets bearing iC3b, a fragment involved in the complement system.^[ref]

With M. L. Dustin, T. A. Springer later investigated how stimulating the T-cell receptor changes adhesion through LFA-1. The 1989 experiments found a rapid, transient increase in adhesion strength. This supplied a mechanism for coordinating target recognition with sticking and subsequent release, rather than treating the presence of an adhesion protein as a fixed measure of how strongly a cell will bind.^[ref]