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21 Cards in this Set
- Front
- Back
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What is the primary role of B lymphocytes during an immune response?
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production of Abs to:
- destroy extracell microorganisms - prevent spreading of intracell pathogens |
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What is the 1st way by which Abs can protect the host?
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Neutralization: Abs bind pathogens to prevent them from entering the cell
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What is the 2nd way by which Abs can protect the host?
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Opsonization: Abs coats pathogen, it can facilitate destruction of pathogens by phagocytic cells
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What is the 3rd way by which Abs can protect the host?
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Activating complement cascade of proteins: complement proteins bound to the surface of pathogen are recognized by receptors expressed on surface of phagocytes (or some components of complement can directly destroy pathogen like gamma TURC)
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How are Abs distributed?
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Abs of different isotypes are adpated to function in different compartment of the body
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IgM characteristics?
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- 1st Ab to be produced
- low affinity but has a lot of binding sites (high avidity) - large size (in blood and lymph) - efficient activation of the complement cascade |
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IgG, IgA, IgE characteristics?
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- smaller, can diffuse from blood to tissue
- IgG and IgE are monomeric - IgA can be dimeric - High affinity |
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IgG?
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- principal isotype in blood and ECF
- opsonization and activation of complement cascade |
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IgA?
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- in secretions (mucus)
- neutralization - less potent in complement cascade |
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IgE?
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- very low in blood and ECF
- bind to receptors on mast cells found beneath skin and mucosa along blood vessels - mediators -> coughing, sneezing and vomiting |
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IgG1?
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transport across placenta
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the fours isoforms of IgG (IgG1-4)?
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diffuse very easily into extravascular sites, along with IgA
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How does IgA transcytose across epithelia?
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- In the lamina propria, IgA is secreted as a dimer and it binds through its Fc portion to the poly-Ig receptor
- It gets internalized and transported to the luminal surface of the epithelial cell - at surface, poly-Ig receptor is cleaved and its extracellular portion (secretory component) remains attached to the Fc portion of the IgA |
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Where are the principle sites of IgA secretion?
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gut, respiratory epithelium, lactating breast, and other exocrine glands such as salivary and tear
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What is IgA primary functional role?
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- protection of epithelia through neutralization
- it is secreted in br milk and transferred to the gut of newborn to protect against newly encountered bacteria |
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How does transplacental transport of IgG occur?
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through bloodstream, due to an IgG transport protein called FcRn which bins to the Fc portion of the Ab
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What are the distriubtion of all isotypes in the body?
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- IgM and IgG in blood
- IgG and monomeric IgA in ECF - Dimeric IgA in secretion across epithelia - IgE just beneath epithelia (associated with mast cells) - |
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What is a toxin?
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Proteins secreted by bacteria
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How do neutralization of bacterial toxins occur?
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- when neutralizing Abs bind to the receptor binding domain of the toxin, preventing from entering the cell
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Which Abs are good at neutralizing?
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IgG are the principal neutr. abs for toxins found in tissues and IgA neutralize toxins at mucosal surfaces
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What can inhibit infectivity of viruses?
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high affinity IgG and IgA can also neutralize virus
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