Beta 2-integrin and L-selectin are obligatory receptors in neutrophil aggregation [see comments]

Abstract

We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope.

The polysaccharide fucoidan inhibits microvascular thrombus formation independently from P‐ and l‐selectin function in vivo

“…L-selectin has been shown to be an obligate adhesion molecule in leukocyte±leukocyte interactions [3] and leukocyte aggregation has been described to occur in suspension in vitro and suggested to contribute to microvascular occlusion in vivo [28,29]. In this study, we observed that passive immunization against L-selectin did not prevent the induction of thrombosis, suggesting that Lselectin plays no substantial role in thrombus formation induced in the microcirculation.…”

Intravascular granulocyte aggregates caused by the selectin‐binding carbohydrate fucoidin in pig kidneys

“…26 The homotypic human granulocyte aggregation experiments performed not only show formation of granulocyte aggregates, but also confirm that fucoidin is a potent antagonist of L-selectinmediated neutrophil-neutrophil adhesion. 34,38 However, both inhibition of L-selectin-mediated homotypic adhesion and macroaggregate formation were observed at concentrations slightly below (30 g/mL) and above (300 g/mL) of those used in in vivo experiments, respectively. Thus, the 'therapeutic window' of fucoidin appears to be rather small.…”

Phosphorylated form of MacMARCKS is essential to LFA-1-dependent cell-cell adhesion of U937 monocytic cells

“…Platelet aggregation plays an essential role in the hemostatic process (Gordon, 1981). In the immune system, homotypic aggregation was also observed with neutrophils (Simon et al, 1993;Okuyama et al, 1996), lymphocytes (Dustin and Springer, 1989;Andrew et al, 1995), and eosinophil (Teixeira et al, 1995). These aggregation events are believed to play important roles in leukocyte trafficking and activation (Rochon and Frojmovic, 1992).…”

“…These aggregation events are believed to play important roles in leukocyte trafficking and activation (Rochon and Frojmovic, 1992). Many types of molecules participate in cell-cell adhesion (for review see [Singer, 1992]), and the ␤2-integrin family of adhesion molecules is an important group among them (Miller et al, 1986;Simon et al, 1993;Petruzzelli et al, 1998). Protein kinase C (PKC) is required for the activation of the ␤2integrin family of adhesion molecules (for review see [Clark and Brugge, 1995;Stewart et al, 1995]).…”