Specificity of membrane complement receptor type three (CR3) for beta-glucans.
The binding of the iC3b receptor (CR3) to unopsonized zymosan was shown to result from CR3 attachment to cell wall beta-glucans. A specificity of neutrophil responses for beta-glucan was first suggested by a comparison of yeast (Saccharomyces cerevisiae) cell wall components for stimulation of a neutrophil superoxide burst. Neutrophils responded poorly to heat-killed yeast, but gave increasingly better responses to cell wall polysaccharides devoid of proteins (zymosan) and nearly pure beta-glucan particles derived from zymosan. Zymosan triggered a burst that was 29% as great as that stimulated by phorbol myristate acetate (PMA), and beta-glucan particles stimulated a burst that was 72% as great as that produced by PMA. Phagocytic responses to yeast were also inhibited by soluble glucans but not by soluble mannans. Three types of experiments demonstrated a role for CR3 in these responses. First, neutrophil ingestion of either yeast or yeast-derived beta-glucan particles was blocked by monoclonal anti-CR3, fluid-phase iC3b, or soluble beta-glucan from barley. Monocyte ingestion of beta-glucan particles was also blocked by anti-CR3, but not by anti-CR1 or anti-C3. Second, the neutrophil superoxide burst response to either zymosan or beta-glucan particles was blocked by anti-CR3 or fluid-phase iC3b, and was completely absent with neutrophils from 3 patients with an inherited deficiency of CR3. Third, CR3 was isolated from solubilized neutrophils by affinity chromatography on beta-glucan-Sepharose.
D005936:Glucans / Q000276:immunology*; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000276:immunology; D066298:In Vitro Techniques; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis; D011956:Receptors, Cell Surface / Q000276:immunology; D011951:Receptors, Complement / Q000276:immunology*; D017463:Receptors, Complement 3b; D011971:Receptors, Immunologic; D012441:Saccharomyces cerevisiae / Q000276:immunology; D013481:Superoxides / Q000378:metabolism; D015054:Zymosan / Q000276:immunology
D005936:Glucans; D011956:Receptors, Cell Surface; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D011971:Receptors, Immunologic; C045268:beta-glucan receptor; D013481:Superoxides; D015054:Zymosan