Ligation of the lactosylceramide receptor (CDw17) promotes neutrophil migration

Abstract

Abstract Introduction: B-Glucan, a β-(1–3) linked glucose polymer, enhances neutrophil anti-infective activity by binding to specific receptors including the lectin site of the CR3 integrin (CD11b/CD18) and the glycosphingolipid lactosylceramide. B-glucan promotes neutrophil chemotaxis towards fMLP and C5a. Enhancement of neutrophil migration to fMLP occurs via CR3 through a p38 dependent mechanism. We investigated the mechanism by which β-glucan promotes neutrophil chemotaxis towards C5a. Methods: Migration was assessed by serum agarose overlay technique using chambered slides precoated or not with β-glucan (100μg/ml). Migration of human neutrophils at 37 C for 2 hours was established towards C5a (10 pmol) using PBS as control. Antibody blocking experiments included neutrophil pretreatment with mAbs specific for CR3 or for CDw17. In some experimental groups neutrophils were treated with the p38 MAP kinase inhibitor SB203580 (10mM) prior to assay. The number of chemotaxing cells was quantified by microscopy. Results: The anti-CDw17 mAb but not anti-CR3 mAb obviated the β-glucan promotion. This finding indicates that lactosylceramide is the β-glucan receptor that mediates enhanced chemotaxis towards C5a. Non-specific isotype antibodies did not affect neutrophil migration. Further, p38-inhibited neutrophils did not demonstrate enhanced migration to C5a in the presence of β-glucan. Conclusions: Ligation of lactosylceramide by β-glucan promoted neutrophil chemotaxis towards C5a signaling through a p38 dependent pathway. This is the first demonstration of the involvement of lactosylceramide in neutrophil chemotaxis. This receptor may prove to be a novel therapeutic target in enhancing neutrophil anti-infective activity.