Binding of human serum amyloid P componentto L‐selectin

Abstract

Serum concentrations of soluble L-selectin by far exceed those of other soluble adhesion molecules, and serum soluble L-selectin concentrations are remarkably stable upon prolonged storage. We present evidence for Ca 2+ -dependent binding interactions between human serum amyloid P (SAP), a proteolysis-resistant pentraxin glycoprotein, and L-selectin, as shown by surface plasmon resonance measurements, protein band shift assays in a native PAGE system, and after SDS-PAGE and membrane transfer. Monoclonal antibodies to L-selectin strongly reduced binding of biotinylated SAP to Lselectin-IgG chimeras immobilized on microtiter plates. As binding was reduced by prior glycopeptidase F treatment of L-selectin but not of SAP, it appears to be based on SAP lectin domain interactions with N-linked L-selectin carbohydrates. In freshly prepared human lymphocytes, SAP incubation induced expression of a b2 integrin neoepitope associated with high-affinity binding. This was partially blocked by preincubation with Fab fragments of two anti-L-selectin antibodies. In flow chamber experiments, SAP inhibited the adherence of human neutrophils to activated endothelium under shear stress. Thus, SAP binds to human L-selectin and affects Lselectin-dependent leukocyte-endothelial interactions.

Serum amyloid P inhibits granulocyte adhesion

“…However, a different group found that SAP inhibits the binding of human granulocyte to TNFα-stimulated human umbilical vein endothelial cells [59]. In this report, we find that SAP does not act as a granulocyte chemoattractant, tends to decrease granulocyte adhesion, and does not affect the percentage of granulocyte expressing CD11b and CD18.…”

“…SAP increases the percentage of neutrophils expressing adhesion molecules such as CD11b and CD18 and the fibronectin receptor α5β1 [58]. In flow chambers, SAP inhibits the binding of human neutrophils to TNFα-stimulated human umbilical vein endothelial cells [59]. Since granulocytes can recognize SAP through Fc receptors, and the reports of the regulation of neutrophil adhesion by SAP seem inconsistent, we examined the effect of SAP on granulocyte adhesion and recruitment to sites of inflammation.…”

Serum amyloid P: a systemic regulator of the innate immune response

“…SAP binds to human and murine neutrophils and decreases TNF-␣-and IL-8-induced neutrophil binding to ECM components [20,21]. SAP also reduces TNF-␣-induced human neutrophil adhesion to endothelial cells [22]. One possible mechanism underlying the effect of SAP on neutrophils involves SAP binding to, and thus, potentially blocking, the adhesion receptor L-selectin on neutrophils [22].…”

Distinct Fcγ Receptors Mediate the Effect of Serum Amyloid P on Neutrophil Adhesion and Fibrocyte Differentiation

“…When this regulation is compromised, the elevated influx of neutrophils and recruitment of other immune cells by activated neutrophils can cause severe organ damage and fibrosis (14–16). SAP binds neutrophils to inhibit their spreading and adhesion to components of extracellular matrix and endothelial cells (12, 17). Injections of SAP decrease the infiltration of neutrophils into the lungs following bleomycin insult in mice (12).…”