Immunoglobulins

• What is an antigen?

  A foreign substance entering the body
• What is an antibody?

  A protein produced to fight antigens
• What analogy is used to describe antigens, antibodies, and the immune system?

  • Thief = Antigen
  • Spotlight = Antibody/Immunoglobulin
  • Police = Immune system
• Where are immunoglobulins synthesized?

  Mainly in plasma cells
• What is the basic structure of immunoglobulin molecules?

  Consists of 4 polypeptide chains
• What are the two types of chains in immunoglobulins?

  Light chains and heavy chains
• How many regions do both heavy and light chains have?

  Two regions
• What are the two regions of heavy and light chains?

  C-Terminal and N-Terminal regions
• How many major classes of immunoglobulins are there?

  Five major classes
• What heavy chain does Immunoglobulin G (IgG) have?

  Gamma (γ) heavy chain
• What heavy chain does Immunoglobulin M (IgM) have?

  Mu (μ) heavy chain
• What heavy chain does Immunoglobulin A (IgA) have?

  Alpha (α) heavy chain
• What heavy chain does Immunoglobulin D (IgD) have?

  Delta (δ) heavy chain
• What heavy chain does Immunoglobulin E (IgE) have?

  Epsilon (ε) heavy chain
• What types of light chains are present in immunoglobulins?

  Kappa (κ) or lambda (λ) light chains
• What percentage of light chains are of κ variety in humans?

  60%
• What percentage of light chains are of λ type in humans?

  40%
• What carbohydrate residues do immunoglobulins contain?

  Mannose, galactose, fructose, N-acetyl neuraminic acid, glucosamine
• What percentage of total immunoglobulins in circulation does IgG constitute?

  75-80%
• What is the major immunoglobulin during the secondary immune response?

  IgG
• What unique ability does IgG have regarding the placenta?

  It can cross the placenta
• What is the opsonization effect of IgG?

  It binds microbes to facilitate phagocytosis
• What is the role of IgG in complement activation?

  It sensitizes target cells for killing
• What form does monomeric IgA take in serum?

  Monomeric form
• What is the form of secretory IgA (SIgA)?

  Dimeric form stabilized by J chain
• Where is SIgA found?

  In seromucous secretions like tears and saliva
• What is the primary function of IgM?

  It acts in the primary immune response
• How many subunits make up IgM?

  Five subunits
• What is the shape of IgM due to its subunits?

  Star shape
• What type of antibodies are natural antibodies?

  IgM in nature
• What happens to a fetus with incompatible antigens regarding natural antibodies?

  The fetus is protected from natural antibodies
• What is the concentration of IgE in serum?

  Very low concentration
• What role does IgE play in the body?

  It mediates allergy and hypersensitivity
• What is the function of IgD?

  Acts as a B cell antigen receptor
• What is the complement system?

  A part of the innate immune system
• How many components are in the complement system?

  Nine components
• What is the overall aim of the complement system?

  To support the immune response
• What are the three ways to activate the complement system?

  The Classical, MBL, and Alternative pathways
• What does C3 convertase do?

  Triggers further effects downstream
• How is the classical pathway activated?

  By C1q binding to a pathogen or complex