Related Experiment Videos
The leukocyte integrin Mac-1 (CD11b/CD18) contributes to binding of human granulocytes to collagen
B Walzog1, D Schuppan, C Heimpel
1Department of Physiology, Free University Berlin, Germany.
Abstract:
Adhesion of polymorphonuclear granulocytes (PMN) to extracellular matrix proteins has been shown to be important for their migration in vitro and is thought to participate in PMN recruitment to sites of inflammation. Isolated human PMN stimulated with PMA were found to adhere best to microtiter wells coated with the novel ECM glycoprotein undulin (27 +/- 3% of PMNs added), followed by fibrinogen (25 +/- 2%), collagen type VI (18 +/- 2%), fibronectin (16 +/- 2%), and laminin (15 +/- 3%). PMN adhesion to other collagens ranged between 3 and 11%. Monoclonal antibodies recognizing CD18 and CD11b subunits of Mac-1 inhibited adhesion of PMN to collagens by an order of magnitude more effectively than to all noncollagenous substrates. F(ab')2 fragments of the anti-CD18 antibody were also able to block adhesion to collagens. Anti-LFA-1 (CD11a) and anti-CD44 antibodies did not significantly reduce adhesion. PMN adhesion was also inhibited by soluble collagens type II and VI (ID50 approximately 75 micrograms/ml). Binding of soluble radiolabeled collagens type II and VI to PMNs was specific and saturable with apparent dissociation constants of 2.2 and 1.9 nM, respectively, and specific binding of collagens type II and VI was almost completely inhibited by anti-CD18, but not by control antibodies. These data indicate that Mac-1 function is required for binding of human PMN to collagens.
Insights
Polymorphonuclear granulocytes (PMN) adhesion to collagen is crucial for inflammation. The study found Mac-1 integrin is essential for this binding, highlighting its role in immune cell recruitment.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Polymorphonuclear granulocytes (PMN) adhesion to extracellular matrix (ECM) proteins is vital for migration and recruitment to inflammatory sites.
- Understanding the molecular mechanisms of PMN adhesion to specific ECM components is crucial for developing targeted anti-inflammatory therapies.
Purpose of the Study:
- To investigate the role of the Mac-1 integrin in the adhesion of human PMN to various ECM proteins, with a focus on collagens.
- To characterize the binding kinetics and specificity of PMN interaction with collagens.
Main Methods:
- Adhesion assays using isolated human PMN and microtiter wells coated with different ECM proteins (undulin, fibrinogen, collagens, fibronectin, laminin).
- Inhibition studies using monoclonal antibodies against integrin subunits (CD18, CD11b, CD11a) and CD44.
- Binding assays with soluble radiolabeled collagens (Type II and VI) to PMN.
Main Results:
- Human PMN exhibited the highest adhesion to undulin and fibrinogen, followed by collagen type VI, fibronectin, and laminin.
- Monoclonal antibodies targeting CD18 and CD11b subunits of Mac-1 significantly inhibited PMN adhesion to collagens, but not to non-collagenous substrates.
- Soluble collagens type II and VI specifically and saturably bound to PMN, and this binding was blocked by anti-CD18 antibodies.
Conclusions:
- Mac-1 integrin function is essential for the adhesion of human PMN to collagens.
- These findings elucidate a key molecular interaction in PMN recruitment to inflammatory sites, mediated by Mac-1 binding to collagenous ECM components.