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IMMUNOGLOBULINS
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Immunoglobulins Structure and Function

Question Answer Article
What are immunoglobulins also known as?
  • Antibodies
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How many domains does the heavy chain have?
  • 1 variable domain
  • 3 or 4 constant domains
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How many domains does the light chain have?
  • 1 variable domain
  • 1 constant domain
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What are hypervariable domains?
  • Folded pockets of the variable domain into which antibody can bind
  • Different antibodies have different amino acid sequences within the three variable domains
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What does Fab stand for and from which chain is it generated?
  • Fragment associated with antigen binding
  • Light chain
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What does Fc stand for and from which chain is it generated?
  • Constant fragment
  • Heavy chain
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What does the Fc fragment do?
  • Mediates phagocytosis
  • Triggers inflammation
  • Targets Ig to certain tissues
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What are the four major effects of antibodies?
  • Blockage and agglutination
  • Promotion of phagocytosis
  • Degranulation of mast cells/eosinophils
  • Complement Fixation
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Classes of Immunoglobulin

Question Answer Article
How do the five classes of immunoglobulins vary from each other?
  • They each have a different composition to their heavy chains
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IgA is specially adapted for function at which type of surface?
  • Mucosal surfaces
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True or False: IgA is a monomer
  • False
  • IgA is a dimer
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What are the functions of IgA?
  • Prevents agents from adhering to the epithelial surfaces as it binds to foreign antigen
  • Resists proteolytic digestion so can function in the gut
  • Does not activate the complement system so helps to preserve mucosal integrity
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In which species has IgD been identified?
  • Ruminants
  • Pigs
  • Dogs
  • Rodents
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What is the main function of IgD?
  • Helps B cell development
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True or False: IgE is not a soluble antibody?
  • True
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What are the functions of IgE?
  • Triggers acute inflammation by causing degranulation
  • Involved in type I hypersensitivity reactions
  • Involved in producing immunity to parasitic worms and nematode parasites
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True or False: IgG is the smallest antibody and can easily leave the plasma and enter tissue?
  • True
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Where is IgG produced?
  • Bone marrow
  • Spleen
  • Lymph nodes
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What is the function of IgG?
  • Activates the classical pathway of the complement cascade
  • Can act as targets for macrophages, eosinophils and neutrophils
  • Causes agglutination and opsonisation of bacteria
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True or False: IgM is a monomer
  • True
  • But it is secreted as a pentamer
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IgM is five times larger than most other antibodies. What effect does this have on its function?
  • Cannot cross the placenta
  • Does not diffuse quickly or enter tissues readily
  • Its concentration in extracellular fluid and lymph is low
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What are the main functions of IgM?
  • Complement activation
  • Agglutination
  • Opsonisation
  • Virus neutralisation
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Immunoglobulins Variation

Question Answer Article
Which genes code for the immunoglobulin subtypes and on which chain are they located?
  • IGH genes
  • Heavy chain
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Complete the sentences about IgG subtypes Humans and rodents have four IgG subtypes. Dogs have three IgG subtypes. Ruminats have three or four IgG subtypes. Link to Answer Article
What are allotypes?
  • Differences in immunoglobulins between individuals of a particular species
  • Allotypes are inheritable
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What are idiotypes?
  • Variations in the sequences of amino acids in the variable regions of the light and heavy chains
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What is immunoglobulin heavy chain switching?
  • After antigenic exposure the IgM+ B-cells differentiate
  • Only after direct influence of T cells
  • Other classes of immunoglobluins are synthesised
  • The same varibale domains are kept
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How do different classes of antibody differ from each other?
  • Size
  • Charge
  • Amino acid composition
  • Associated carbohydrate
  • Function
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