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Surfactant protein A binds to IgG and enhances phagocytosis of IgG-opsonized erythrocytes

Surfactant protein A binds to IgG and enhances phagocytosis of IgG-opsonized erythrocytes Surfactant protein (SP)-A and SP-D, immunoglobulins, and complement all modulate inflammation within the lung by regulating pathogen clearance. For example, SP-A binds to and opsonizes a variety of bacteria and viruses, thereby enhancing their phagocytosis by innate immune cells such as alveolar macrophages. Immunoglobulins, which bind to antigen and facilitate Fc receptor-mediated phagocytosis, can also activate complement, a family of soluble proteins with multiple host defense functions. Previous studies showed that SP-A and complement protein C1q interact. Since complement protein C1q binds to IgG and IgM immune complexes, the hypothesis tested in this study was that SP-A, which is structurally homologous to C1q, also binds to IgG and affects its functions. SP-A binds to the Fc, rather than the Fab, region of IgG. Binding is calcium dependent but not inhibited by saccharides known to bind to SP-A's carbohydrate recognition domain. The binding of SP-A does not inhibit the formation of immune complexes or the binding of IgG to C1q. In contrast, SP-A enhances the uptake of IgG-coated erythrocytes, suggesting that SP-A might be influencing Fc receptor-mediated uptake. In summary, this study shows a novel interaction between SP-A and IgG and a functional consequence of the binding. collectin; immune complex; innate immunity; lung Address for reprint requests and other correspondence: J. R. Wright, Box 3709, Dept. of Cell Biology, Duke Univ. Medical Center, Durham, NC 27710 (e-mail: j.wright@cellbio.duke.edu ) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Lung Cellular and Molecular Physiology The American Physiological Society

Surfactant protein A binds to IgG and enhances phagocytosis of IgG-opsonized erythrocytes

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
1040-0605
eISSN
1522-1504
DOI
10.1152/ajplung.00188.2006
pmid
17090701
Publisher site
See Article on Publisher Site

Abstract

Surfactant protein (SP)-A and SP-D, immunoglobulins, and complement all modulate inflammation within the lung by regulating pathogen clearance. For example, SP-A binds to and opsonizes a variety of bacteria and viruses, thereby enhancing their phagocytosis by innate immune cells such as alveolar macrophages. Immunoglobulins, which bind to antigen and facilitate Fc receptor-mediated phagocytosis, can also activate complement, a family of soluble proteins with multiple host defense functions. Previous studies showed that SP-A and complement protein C1q interact. Since complement protein C1q binds to IgG and IgM immune complexes, the hypothesis tested in this study was that SP-A, which is structurally homologous to C1q, also binds to IgG and affects its functions. SP-A binds to the Fc, rather than the Fab, region of IgG. Binding is calcium dependent but not inhibited by saccharides known to bind to SP-A's carbohydrate recognition domain. The binding of SP-A does not inhibit the formation of immune complexes or the binding of IgG to C1q. In contrast, SP-A enhances the uptake of IgG-coated erythrocytes, suggesting that SP-A might be influencing Fc receptor-mediated uptake. In summary, this study shows a novel interaction between SP-A and IgG and a functional consequence of the binding. collectin; immune complex; innate immunity; lung Address for reprint requests and other correspondence: J. R. Wright, Box 3709, Dept. of Cell Biology, Duke Univ. Medical Center, Durham, NC 27710 (e-mail: j.wright@cellbio.duke.edu )

Journal

AJP - Lung Cellular and Molecular Physiology – The American Physiological Society

Published: Dec 1, 2006

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