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Blood Cells Mol Dis. 2009 May-Jun;42(3):177-84. doi: 10.1016/j.bcmd.2009.01.006. Epub 2009 Feb 25.

Activation of human neutrophil Mac-1 by anion substitution.

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Department of Pharmacology and Physiology, School of Medicine, University of Rochester, Rochester, NY 14642, USA.


Substituting the medium chloride with glucuronate or glutamate causes a rapid, 10 to 30-fold, increase in the binding of the monoclonal antibody, CBRM1/5, which recognizes the high-affinity conformation of the Mac-1 integrin. This change is reflected in functional adhesion assays that show increased adhesion to ICAM-1 coated beads. Blocking antibodies indicate that the increased adhesion is almost entirely due to Mac-1. The inhibitor NPPB (100 microM) reduces Cl(-) efflux into low Cl(-) medium by 75%, and blocks increased CBRM1/5 binding after stimulation with fMLP or TNF-alpha, but has no effect on the anion substitution induced increase in CBRM1/5 binding or adhesion to immobilized ICAM-1. Thus, changes in external anion composition, not internal chloride or increases in Cl(-) efflux, are responsible for Mac-1 activation. This effect is substantial. The percentage of Mac-1 in the high affinity state approaches 100% in glutamate and 50% in glucuronate, a far greater response than what is observed after stimulation with fMLP.

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