Direct evidence for two affinity states for lymphocyte function-associated antigen 1 on activated T cells

B. A. Lollo, K. W.H. Chan, E. M. Hanson, V. T. Moy, A. A. Brian

Research output: Contribution to journalArticle

179 Scopus citations

Abstract

Lymphocytes activated by antigen receptor cross-linking or phorbol esters adhere avidly to surfaces bearing intercellular adhesion molecule 1 (ICAM-1) through the adhesion receptor lymphocyte function-associated antigen 1 (LFA-1). It is not known whether avid adhesion by stimulated lymphocytes is due to higher affinity binding of ICAM-1 or due solely to post-receptor mechanisms. We have used a recombinant, soluble form of the ICAM-1 molecule to measure the affinity of binding to LFA-1 on unstimulated T cells and T cells stimulated with phorbol esters. The affinity was found to be too low for direct measurements, requiring instead the use of competition protocols in which ICAM-1 competes for binding with radiolabeled Fab from a monoclonal antibody specific for LFA-1. By analysis of the equilibrium and kinetics of competitive binding, we found that the affinity on unstimulated T cells is very low, about 100 μM. Activation of the T cells by phorbol esters caused a small increase in average binding affinity. Further analysis suggested that the change in average affinity reflected the conversion of a fraction of LFA-1 molecules to a state with a 200-fold higher affinity.

Original languageEnglish (US)
Pages (from-to)21693-21700
Number of pages8
JournalJournal of Biological Chemistry
Volume268
Issue number29
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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