title: Complement and antibody participation in opsonophagocytosis of type IV and V group B streptococci.
abstract: Requirements for complement and antibody in neutrophil-mediated killing of serotype IV and V group B streptococci were investigated. Neutrophils from adults were tested in an opsonophagocytic assay with sera from healthy adults, healthy newborns, and hypogammaglobulinemic, agammaglobulinemic, and C4-deficient patients. For all serum sources, the bactericidal index for both serotypes exceeded 84% after 40 min of incubation. Heat inactivation of sera ablated killing. Blockade of neutrophil receptor FcIII effected a maximum of 16% inhibition of opsonophagocytosis, and FcII receptor blockade demonstrated negligible inhibition. When neutrophil complement receptor 1 or 3 blockade was employed, the maximum inhibition detected was 26%. Simultaneous blockade of complement receptors 1 and 3 effected maximum inhibition levels of 25 and 65% for serotypes IV and V, respectively. Blockade of complement receptor 3 and neutrophil receptor FcIII inhibited opsonophagocytosis by 56% for both serotypes. When serum complement concentrations were restricted, neutrophil-mediated killing diminished but was restored by the addition of hyperimmune rabbit antiserum. These findings suggest that complement and antibody are major participants in the opsonophagocytosis of serotypes IV and V group B streptococci. A low prevalence of carriage or mediation of efficient phagocytosis by interactions of neutrophil complement and Fc receptors may contribute to the rarity of human infections caused by these two serotypes.
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: M A
authors.initials: MA
authors.lastname: Hall
authors.forename: M S
authors.initials: MS
authors.lastname: Edwards
authors.forename: C J
authors.initials: CJ
authors.lastname: Baker
mesh_terms: D000328:Adult; D000818:Animals; D000907:Antibodies, Bacterial / Q000502:physiology*; D002648:Child; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D008297:Male; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis; D011817:Rabbits; D011961:Receptors, Fc / Q000502:physiology; D013292:Streptococcus agalactiae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D011961:Receptors, Fc; D003165:Complement System Proteins