Immunology

• How are cells recognised by the body?

  Glycoproteins and glycolipids
• What are some physical and chemical barriers against pathogens?

  • Skin
  • Mucus membranes
  • Saliva
  • Tears (containing lysozyme)
• What is an antigen?

  A marker on cells and pathogens, allowing the body to distinguish them as 'non-self'.
• Why do pathogens show antigen variability?

  Genetic mutations
• What are the main types of phagocytes?

  Neutrophils and macrophages
• What occurs in phagocytosis?

  1. Chemotaxic attraction to pathogen
  2. Phagocyte binds to the pathogen
  3. Pathogen is endocytosed
  4. Phagosome forms with a lysosome forming a phagolysosome
  5. Pathogen is digested and antigens are displayed on the phagocyte membrane
• Where do T cells mature?

  Thymus
• When is a T cell activated?

  When it recognises and binds with a 'non-self' antigen, they then undergo mitosis to increase in number
• What is an antigen-presenting cell?

  A host cell that has been invaded by a pathogen and is now displaying the antigens on its membrane
• What do T helper cells do?

  They assist other blood cells in the immune response and release cytokines to stimulate maturation of B plasma cells, production of B memory cells, and activate cytotoxic T cells.
• What is the role of cytotoxic T cells?

  They attach to cells presenting pathogenic antigens and secrete toxic substances that kill the pathogens inside and the cells along with it through holes created by 'perforins'.
• Where do B cells mature?

  Bone marrow
• What do B cells contain?

  The genes to code for antibodies
• Each type of B cell produces only one specific antigen
• What happens in the B cell response?

  1. Only one B cell has the specific antibody receptor to an antigen
  2. The selected B cell undergoes mitosis into plasma or memory cells
  3. Plasma cells secrete the antibody that is complementary to the pathogenic antigen.
• What are antibodies ?

  Globular glycoproteins called immunoglobulins
• What kind of structure do antibodies have?

  Quaternary, two light and two heavy chains
• Constant antibody regions do not vary, whereas the polypeptide of the variable region does, producing different quaternary structures
• What is the epitope?

  The region of the antigen that binds with the antibody
• What is the purpose of the hinge region?

  To give flexibility to the antigen binding site
• What bonds are present between heavy chains?

  Disulfide bridges
• What happens in agglutination?

  Antibodies bind to more than one pathogen, causing pathogens to clump together, creating an excellent marker for phagocytes.
• What is the role of B memory cells?

  They form an immunological memory to create a faster secondary response to an antigen.
• What happens when a B memory cell is activated?

  They rapidly divide and differentiate into B plasma cells to produce antibodies.
• What are the two types of vaccine?

  Live attenuated or inactivated
• How do vaccines work?

  They produce long term immunity as they cause memory cells to be created, providing the immune system with a faster more efficient response.
• What is contained within a live attenuated vaccine?

  Whole pathogens that have been 'weakened'.
• What is contained in an inactive vaccine?

  Whole pathogens that have been killed, or subunits of the pathogens.
• When does herd immunity arise?

  When a sufficiently large proportion of the has been vaccintated, making it difficult for a pathogen to spread within a population.
• Why does eradicating disease prove to be a challenge?

  • Pathogens are highly complex
  • Too few in a population may have been vaccinated
  • Lack of public health facilities
• What can the success of the smallpox eradication be attributed to?

  • Stability of the virus
  • The vaccine was a live attenuated one
  • Vaccines were easily transported
  • Symptoms of the virus were easily identified
  • The disease only affects humans meaning no other species are carriers
  • Consistency of effort of vaccination, surveillance, containment of outbreaks.
• What is active immunity?

  Immunity accquired when an antigen enters the body triggering a specific immune response.
• Active immunity can be natural or through administration of a vaccine (artificial)
• What is passive immunity?

  Immunity accquired without an immune response.
• Natural passive immunity occurs when babies recieve antibodies from placenta or breastmilk, artificial passive immunity is when an individual is given an injection/transfusion of anttibodies or antitoxins.
• How is HIV transmitted?

  Sex, blood donations, sharing needles, from mothers to daughters in placenta or breastmilk, any sharing of blood.
• What is the structure of HIV?

  • Two RNA strands
  • Proteins/enzymes
  • Protein coat/capsid
  • Viral envelope (bilayer and glycoproteins)
  • Attachment proteins
• How does HIV multiply?

  1. Viral RNA enters the lymphocyte
  2. Reverse transcriptase enzymes produce a DNA copy of the viral RNA
  3. The DNA copy is inserted into the chromosomes
  4. Each time the cell multiplies, viral DNA is copied.
• When will HIV positive cells become active?

  HIV will take control of the lymphocyte, producing more HIV particles. The T helper cell dies and new HIV particles are released to infect other lymphocytes.
• How does HIV lead to AIDS?

  • T helper cells are destoyed
  • B cells can no longer be activated
  • Advanced AIDS occurs when individuals can no longer produce antibodes (immuno-compromised)