The cellular responses induced by the capsular polysaccharide of Cryptococcus neoformans differ depending on the presence or absence of specific protective antibodies.
The capsule of Cryptococcus neoformans, the principal virulence factor of this fungus, is composed primarily of polysaccharide. The predominant component of the polysaccharide capsule is glucuronoxylomannan (GXM), a compound with potent immunoregulatory properties. GXM is bound and internalized by natural immune cells affecting innate and subsequent adaptive immune response. The cellular pattern recognition receptors involved in GXM binding include toll-like receptor (TLR)4, CD14, TLR2, CD18, Fc gamma receptor II (FcgammaRPi). This multiple cross-linking leads to a suppressive outcome that is arrested and even reversed by protective antibodies to GXM. This review analyzes the immunosuppressive effects induced by capsular material, considering its pattern recognition receptors, and dissects the mechanism of monoclonal antibody shifting to immunoactivation.
Vecchiarelli
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Microbiology Section, Department Of Experimental Medicine And Biochemical Sciences, University Of Perugia, Italy. vecchiar@unipg.it
D000908:Antibodies, Fungal / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000946:Antigens, Fungal / Q000276:immunology; D018821:CD18 Antigens / Q000276:immunology; D002473:Cell Wall / Q000737:chemistry; D003455:Cryptococcus neoformans / Q000737:chemistry* / Q000276:immunology* / Q000472:pathogenicity; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects; D007113:Immunity, Innate; D007165:Immunosuppression Therapy; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008213:Lymphocyte Activation; D018448:Models, Immunological; D011134:Polysaccharides / Q000276:immunology* / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology; D017452:Receptors, IgG / Q000276:immunology; D037521:Virulence Factors / Q000276:immunology
D000908:Antibodies, Fungal; D000911:Antibodies, Monoclonal; D000946:Antigens, Fungal; D018821:CD18 Antigens; D018950:Lipopolysaccharide Receptors; D011134:Polysaccharides; D011956:Receptors, Cell Surface; D017452:Receptors, IgG; D037521:Virulence Factors