Central Role of Complement in Passive Protection by Human IgG1 and IgG2 Anti-pneumococcal Antibodies in Mice

Streptococcus pneumoniae is an important cause of morbitity and mortality worldwide. Capsule-specific IgG1 and IgG2 Abs are induced upon vaccination with polysaccharide-based vaccines that mediate host protection. We compared the protective capacity of human recombinant serogroup 6-specific IgG1 and...

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Bibliographic Details
Published in:The Journal of immunology (1950) 2003-06, Vol.170 (12), p.6158-6164
Main Authors: Saeland, Eirikur, Vidarsson, Gestur, Leusen, Jeanette H. W, van Garderen, Evert, Nahm, Moon H, Vile-Weekhout, Henriette, Walraven, Vanessa, Stemerding, Annette M, Verbeek, J. Sjef, Rijkers, Ger T, Kuis, Wietse, Sanders, Elisabeth A. M, van de Winkel, Jan G. J
Format: Article
Language:English
Subjects:
Animals
Antibodies, Bacterial - administration & dosage
Antibodies, Bacterial - metabolism
Antibody Specificity
Complement System Proteins - metabolism
Complement System Proteins - physiology
Humans
Immunization, Passive - methods
Immunoglobulin G - administration & dosage
Immunoglobulin G - metabolism
Lung - immunology
Lung - microbiology
Lung - pathology
Mice
Mice, Inbred BALB C
Mice, Inbred C57BL
Mice, Knockout
Pneumonia, Pneumococcal - genetics
Pneumonia, Pneumococcal - immunology
Pneumonia, Pneumococcal - pathology
Pneumonia, Pneumococcal - prevention & control
Polysaccharides, Bacterial - immunology
Receptors, IgG - metabolism
Sepsis - genetics
Sepsis - immunology
Sepsis - pathology
Sepsis - prevention & control
Spleen - immunology
Spleen - microbiology
Spleen - pathology
Streptococcus pneumoniae - immunology
Streptococcus pneumoniae - pathogenicity
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Summary:Streptococcus pneumoniae is an important cause of morbitity and mortality worldwide. Capsule-specific IgG1 and IgG2 Abs are induced upon vaccination with polysaccharide-based vaccines that mediate host protection. We compared the protective capacity of human recombinant serogroup 6-specific IgG1 and IgG2 Abs in mice deficient for either leukocyte FcR or complement factors. Human IgG1 was found to interact with mouse leukocyte FcR in vitro, whereas human IgG2 did not. Both subclasses induced complement activation, resulting in C3c deposition on pneumococcal surfaces. Passive immunization of C57BL/6 mice with either subclass before intranasal challenge with serotype 6A induced similar degrees of protection. FcgammaRI- and III-deficient mice, as well as the combined FcgammaRI, II, and III knockout mice, were protected by passive immunization, indicating FcR not to be essential for protection. C1q or C2/factor B knockout mice, however, were not protected by passive immunization. Passively immunized C2/factor B(-/-) mice displayed higher bacteremic load than C1q(-/-) mice, supporting an important protective role of the alternative complement pathway. Spleens from wild-type and C1q(-/-) mice showed hyperemia and thrombotic vessel occlusion, as a result of septicemic shock. Notably, thrombus formation was absent in spleens of C2/factor B(-/-) mice, suggesting that the alternative complement pathway contributes to shock-induced intravascular coagulation. These studies demonstrate complement to play a central role in Ab-mediated protection against pneumococcal infection in vivo, as well as in bacteremia-associated thrombotic complications.
ISSN:0022-1767
1550-6606
DOI:10.4049/jimmunol.170.12.6158