ABSTRACT
Several of the most significant bacterial pathogens in humans, including Streptococcus pyogenes, express surface proteins that bind IgG antibodies via their fragment crystallizable (Fc) region, and the dogma is that this protects the bacteria against phagocytic killing in blood. However, analysis of samples from a patient with invasive S. pyogenes infection revealed dramatic differences in the presence and orientation of IgG antibodies at the surface of bacteria from different sites. In the throat, IgG was mostly bound to the bacterial surface via Fc, whereas in the blood IgG was mostly bound via fragment antigen-binding (Fab). In infected and necrotic tissue, the Fc-binding proteins were removed from the bacterial surface. Further investigation showed that efficient bacterial IgGFc-binding occurs only in IgG-poor environments, such as saliva. As a consequence, the bacteria are protected against phagocytic killing, whereas in blood plasma where the concentration of IgG is high, the antibodies preferentially bind via Fab, facilitating opsonization and bacterial killing. IgG-poor environments represent the natural habitat for IgGFc-binding bacteria, and IgGFc-binding proteins may have evolved to execute their function in such environments. The lack of protection in plasma also helps to explain why cases of severe invasive infections with IgGFc-binding bacteria are so rare compared with superficial and uncomplicated infections.
Subject(s)
Antibodies, Bacterial/metabolism , Fasciitis, Necrotizing/immunology , Fasciitis, Necrotizing/microbiology , Streptococcal Infections/immunology , Streptococcal Infections/microbiology , Streptococcus pyogenes/immunology , Streptococcus pyogenes/pathogenicity , Adult , Amino Acid Sequence , Antibodies, Bacterial/blood , Antibodies, Bacterial/classification , Antibodies, Bacterial/genetics , Antigens, Bacterial/genetics , Antigens, Bacterial/metabolism , Bacterial Outer Membrane Proteins/genetics , Bacterial Outer Membrane Proteins/metabolism , Branchial Region/immunology , Branchial Region/microbiology , Carrier Proteins/genetics , Carrier Proteins/metabolism , Cell Membrane/immunology , Complement System Proteins/metabolism , Fasciitis, Necrotizing/genetics , Female , Humans , Immunoglobulin Fab Fragments/metabolism , Immunoglobulin Fc Fragments/metabolism , Immunoglobulin G/blood , Immunoglobulin G/classification , Immunoglobulin G/genetics , Immunoglobulin G/metabolism , Microscopy, Immunoelectron , Molecular Sequence Data , Neutrophils/immunology , Neutrophils/microbiology , Phagocytosis , Sequence Homology, Amino Acid , Shock, Septic/genetics , Shock, Septic/immunology , Shock, Septic/microbiology , Streptococcal Infections/genetics , Streptococcus pyogenes/genetics , Streptococcus pyogenes/ultrastructureABSTRACT
The localization of vasoactive intestinal polypeptide (VIP)-immunoreactive (ir) nerve cell bodies and fibers has been studied in the gill arches of goldfish (Carassius auratus, L.) using the peroxidase-antiperoxidase (PAP) immunohistochemical method. It was found that VIP-ir nerve cell bodies are localized in connective tissue on the oral side of the gill arch; these cells were present as single cells, in couples or as small clusters. Moreover, a dense network of VIP-ir fibers was observed beneath the lining epithelium of the raker cushion. The possible involvement of this peptide in mucus secretion in the gill arches of teleost is discussed.
Subject(s)
Branchial Region/innervation , Gills/innervation , Goldfish/anatomy & histology , Neurons/cytology , Vasoactive Intestinal Peptide/immunology , Animals , Branchial Region/cytology , Branchial Region/immunology , Gills/anatomy & histology , Gills/immunology , Glossopharyngeal Nerve/cytology , Glossopharyngeal Nerve/immunology , Goldfish/metabolism , Immunohistochemistry , Neurons/immunology , Vagus Nerve/cytology , Vagus Nerve/immunologyABSTRACT
The terrestrial survival of birds and mammals depends on evolutionary chantes in cloacal bursae and gill pouches. Comparative dissections of these pouches provide insight into the coordinated functions of cervical endocrine organs, especially as they affect lymphoid tissue.
