Low affinity of cell surface lymphocyte function-associated antigen-1 (LFA-1) generates selectivity for cell-cell interactions.
We examined binding of soluble intercellular adhesion molecule-1 (ICAM-1) dimers and a range of ICAM-1-coated particles to activated T cells. Lymphocyte function-associated antigen-1 (LFA-1) on the surface of activated T cells did not bind soluble ICAM-1 dimers with high affinity. In contrast, activated T cells adhered avidly to ICAM-1-coated planar surfaces. Between these two extremes, a range of ICAM-1-bearing particles was tested for binding. Activated T cells bound particles of 1-microm diameter or larger, but did not bind particles of 0.5-microm diameter or smaller. This threshold was eliminated, and all forms of ICAM-1 bound to LFA-1 when LFA-1 was converted to a high affinity form with an activating antibody. We show that high affinity LFA-1 is generated only as a consequence of an initial low affinity interaction of LFA-1 with ICAM-1 under physiological conditions. Therefore, the selectivity of cell surface LFA-1 for cell-sized particles bearing ICAM-1 appears to be due to the maintenance of low affinity LFA-1 on the surface of activated T cells. These findings alter the definition of inside-out signaling for LFA-1.
Ganpule
G
G
Center for Immunology and the Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Knorr
R
R
Miller
J M
JM
Carron
C P
CP
Dustin
M L
ML
D002448:Cell Adhesion / Q000276:immunology; D002450:Cell Communication / Q000276:immunology*; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000276:immunology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1