title: Differential binding of acapsulate and encapsulated strains of Cryptococcus neoformans to human neutrophils.
abstract: Investigations into mechanisms of binding of encapsulated and acapsulate strains of Cryptococcus neoformans by human neutrophils were performed, using a monolayer assay. The two strains bound to neutrophils by different mechanisms although both had an absolute requirement for opsonization with complement components in normal human serum for binding to occur. Neutrophil binding of encapsulated yeasts required conformational changes in actin yet did not appear to lead to phagocytosis of the organism. A maximum of 12 acapsulate cells bound per neutrophil compared with only four encapsulated yeasts. Cytochalasin D treatment reduced the maximum numbers able to bind per neutrophil by 50%. The encapsulated cryptococci appeared to compete with each other for binding to neutrophils whereas the acapsulate yeast cells bound to neutrophils in an approximately Poisson distribution, suggesting independent binding. Binding of acapsulate cryptococci did not require actin filaments and appeared to trigger phagocytosis. Thus, the capsule of C. neoformans appeared to inhibit binding and internalization by neutrophils.
authors.affiliation: Department of Dermatology, University of Glasgow, UK.
authors.forename: M D
authors.initials: MD
authors.lastname: Richardson
authors.forename: L J
authors.initials: LJ
authors.lastname: White
authors.forename: I C
authors.initials: IC
authors.lastname: McKay
authors.forename: G S
authors.initials: GS
authors.lastname: Shankland
mesh_terms: D000199:Actins / Q000502:physiology; D000704:Analysis of Variance; D003165:Complement System Proteins / Q000276:immunology; D003455:Cryptococcus neoformans / Q000276:immunology* / Q000472:pathogenicity / Q000648:ultrastructure; D015638:Cytochalasin D / Q000494:pharmacology*; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D016177:Macrophage-1 Antigen / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D017463:Receptors, Complement 3b / Q000276:immunology
chemical_list: D000199:Actins; D016177:Macrophage-1 Antigen; D017463:Receptors, Complement 3b; D015638:Cytochalasin D; D003165:Complement System Proteins