title: K-antigen-specific, but not O-antigen-specific natural human serum antibodies promote phagocytosis of Klebsiella pneumoniae.
abstract: Infections due to Klebsiella pneumoniae and other Klebsiella spp. are a leading cause of hospital-associated morbidity, especially in the intensive care setting. In this study, the hypothesis that normal human sera contain sufficient concentrations of K-antigen-specific antibodies to promote phagocytic killing of encapsulated, highly virulent Klebsiella organisms was tested. K2-antigen-specific IgG and IgM antibodies were detected in each of 10 normal sera, and such antibodies were functionally active in a phagocytic killing assay. Phagocytosis depended critically on sufficient numbers of neutrophils and was impaired by the presence of soluble Klebsiella capsular polysaccharide (CPS). Thus, insufficient numbers of neutrophils and circulation of soluble CPS but not lack of K-specific antibodies may be detrimental in Klebsiella sepsis. The efficacy of hyperimmune sera might be based not on enhancement of phagocytosis but on the neutralization of these detrimental effects of circulating CPS and LPS.
authors.affiliation: Department of Medical Microbiology and Hygiene, University Hospital Ulm, 89075 Ulm, Germany.
authors.forename: Philipp M
authors.initials: PM
authors.lastname: Lepper
authors.forename: Angelika
authors.initials: A
authors.lastname: Möricke
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Held
authors.forename: E Marion
authors.initials: EM
authors.lastname: Schneider
authors.forename: Matthias
authors.initials: M
authors.lastname: Trautmann
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001770:Blood Bactericidal Activity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019081:O Antigens / Q000276:immunology*; D010587:Phagocytosis
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D000954:Antigens, Surface; C030659:K antigens; D019081:O Antigens