Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells.

摘要: When phagocyte CR3 binds to iC3b on bacteria or yeast, phagocytosis and degranulation are triggered because of simultaneous recognition via a CD11b I-domain binding site specific microbial polysaccharides lectin located COOH-terminal the I-domain. By contrast, when natural killer (NK) cell adheres erythrocytes tumor cells that lack CR3-binding membrane polysaccharides, neither lysis nor cytotoxicity stimulated. This investigation showed soluble CR3-specific such as beta-glucan induced primed state could trigger killing iC3b-target were otherwise resistant cytotoxicity. Anti-CR3 added before sugars prevented priming, whereas anti-CR3 after blocked attachment iC3b-targets. Polysaccharide priming required tyrosine kinase(s) magnesium-dependent conformational change exposed CBRM1/5 activation epitope. Unlike LPS cytokines, did not up-regulate neutrophil expression expose mAb 24 reporter epitope representing high affinity ICAM-1-binding state. The current data apparently explain mechanism tumoricidal beta-glucans used for immunotherapy. These function through NK CR3, receptor neoplastic tissues frequently targeted with sparing normal iC3b.