title: Complement-mediated serum activities against genetically defined capsular transformants of Haemophilus influenzae.
abstract: Although there are six different capsular serotypes of Haemophilus influenzae (a-f), only type b strains commonly cause systemic infections in man. The present study was performed to determine whether the propensity of the type b organism to cause invasive infections is due to a unique ability to evade complement-mediated host defenses. The ability of genetically defined capsular transformants (a-f) of an unencapsulated H. influenzae to resist the bactericidal and opsonic activities of serum was examined. The unencapsulated organism and the type f transformants were relatively susceptible to serum bactericidal activity in both adult and infant serum pools, the type a and e transformants were relatively resistant, and the types b, c and d transformants were intermediate. With respect to serum opsonic activity in both adult and infant serum pools, the unencapsulated organism and the type f transformant were relatively susceptible, the type a, b and e transformants were relatively resistant and the type c and d transformants were intermediate. Thus, although the type b capsule endows the organism with the ability to resist the bactericidal and opsonic effects of complement, this property is not unique to type b.
authors.affiliation: Department of Pediatrics, School of Medicine, Johns Hopkins University, Baltimore, Maryland.
authors.forename: A J
authors.initials: AJ
authors.lastname: Swift
authors.forename: E R
authors.initials: ER
authors.lastname: Moxon
authors.forename: A
authors.initials: A
authors.lastname: Zwahlen
authors.forename: J A
authors.initials: JA
authors.lastname: Winkelstein
mesh_terms: D000328:Adult; D001770:Blood Bactericidal Activity; D002473:Cell Wall / Q000276:immunology* / Q000382:microbiology; D002675:Child, Preschool; D003165:Complement System Proteins / Q000502:physiology*; D004352:Drug Resistance, Microbial / Q000235:genetics / Q000276:immunology; D006192:Haemophilus Infections / Q000097:blood / Q000276:immunology / Q000382:microbiology; D006193:Haemophilus influenzae / Q000145:classification / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007223:Infant; D009895:Opsonin Proteins / Q000032:analysis; D014169:Transformation, Bacterial
chemical_list: D009895:Opsonin Proteins; D003165:Complement System Proteins