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Published online before print July 7, 2004

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© by The Society for Leukocyte Biology
Journal of Leukocyte Biology, doi:10.1189/jlb.0204077

Received for publication February 9, 2004.
Revised May 28, 2004.
Accepted for publication May 31, 2004.

Article

Direct quantification of the modulation of interaction between cell- or surface-bound LFA-1 and ICAM-1

Laboratoire d’Immunologie, INSERM U600, CNRS FRE 2059, Univ. Mediterranée, Hôpital de Ste-Marguerite, Marseille, Cedex, France

^@ To whom correspondence should be addressed. E-mail: bongrand{at}marseille.inserm.fr.

	Abstract

The functional activity of leukocyte integrins is highly regulated by several mechanisms related to intrinsic molecular properties and receptor interaction with the cell membrane. Here, we present a microkinetic study of the lymphocyte function-associated antigen-1-mediated interaction between flowing Jurkat cells and surface- or cell-bound intercellular adhesion molecule-1 (ICAM-1). We conclude that adhesion is initiated by the formation of a single bond with 0.3 s^-1 dissociation rate, and attachment is subsequently strengthened by the formation of additional bonds during the next 10 s; exposing cells to Mg²⁺ or Mn²⁺ resulted in up to a 16-fold increase of the binding frequency, in line with reported measurements performed on isolated molecules with surface plasmon resonance methodology; cell-bound ICAM-1 molecules were more efficient in mediating adhesion than Fc-ICAM-1, properly oriented and bound by surface-adsorbed protein A; and quantitative analysis of binding frequency suggested that adhesion efficiency was ten- to 100-fold lower than the maximum value allowed by previously determined association rates of soluble molecules. It is concluded that the presented methodology provides a simple and unique way of dissecting the initial step of cell adhesion and discriminating between affinity and avidity modulation of adhesion receptors.

Key Words: laminar flow chamber • confocal microscopy • receptor topography • avidity • dissociation rate