Introduction to Immunology

• Where do B cells and T cells originate and where do they go to?

  Both from bone marrow

  B cells go to secondary lymphoid organs

  T cells go to thymus

  
  

  (These are highly specialised white blood cells)

  
• What are the 2 types of T cells, what do they do?

  Helper T cells : Boost immune response by activating B cells to produce antibodies

  
  

  Cytotoxic T cells : Recognise and destroy infected cells
• What is the immune system?

  Vast communication network of cells and chemical signals distributed in blood and tissues throughout the human body which regulates normal growth and development of the organism while protecting against disease
• What are your secondary lymphoid organs & tissues?

  Tonsils & adenoids

  Bronchus-associated lymphoid tissue

  Spleen

  Lymphoid nodule

  Mesenteric lymph nodes

  Peyer's patch

  Urogenital lymphoid tissue

  
• What is immunity?

  Condition/process in humans that permits innate & acquired resistance to disease

  The host needs to recognise non-self (microbes) components & eliminate them
• What are the requirements for an effective immune system?

  Must recognise wide range of infectious microorganisms including "new" ones

  
  

  Defend against both intracellular & extracellular pathogens (tolerate commensals)

  
  

  Prevent or limit damage to self

  
  

  Respond quickly
• What are dendritic cells?

  antigen presenting cells

  
• What are macrophages?

  Cells that are able to phagocytose and activate bactericidal mechanisms.

  Can also be antigen presenting

  
• What are the 2 immune systems?

  innate and adaptive

  
• What are neutrophils?

  Also undergo phagocytosis

  
• What are mast cells?

  Release histamine and active agents

  
• What is the complement system?

  serum proteins produced by the liver that are activated by cascade to attach to pathogen surface, recruit inflammatory cells and kill pathogens.

  
  

  3 Pathways:

  
  

  1. Classical pathway

  2.MB-LECTIN pathway

  3.Alternative pathway

  
• What does an infection involve?

  
• What epithelial barriers and measures aid innate immunity to stop a pathogen from even entering the body?

  Skin

  Coughing and sneezing

  Stomach acid (chemical)

  Commensal flora

  Saliva (chemical barrier)

  
• If pathogens do somehow manage to enter the body, what defensive barriers do your body have to stop it infecting you?

  Hydrochloric acid & enzymes in stomach

  Commensal flora in gut
• If a pathogen manages to get past all of the epithelial barriers, what happens then?

  Classical pathway only activated if it's a known pathogen and the antibodies are already there

  
• What are anaphylatoxins?

  Fragments (C3a, C4a and C5a) that are produced as part of the activation of the complement system and they trigger mast cell degranulation
• What are pattern recognition receptors?

  Receptors found on cells of the innate immune system. Which recognise pathogen associated molecular patterns.

  
  

  They are not selective and bind to a variety of proteins (PAMPs) found on the surface of many pathogens.
• what happens if the pathogen is able to survive the complement system?

  Phagocytosis occurs by the following cells:

  
  

  -Monocytes (in blood)

  -Neutrophils (in blood)

  -Macrophages (in tissue)

  -Dendritic cells (in tissues & blood)
• Describe the process of phagocytosis.

  1. Macrophages recruited to the site of infection by chemokines and complement system.

  
  

  2. Phagocyte binds to microbe: pattern recognition, opsonisation (C'/Ab)

  
  

  3. microbe is internalised forming the phagosome. (phagocytosis)

  
  

  4. Fusion of phagosome with lysosome: phagolysosome

  
  

  5. Killing of microbe with nitrogen oxide, oxide products (that are inside of phagolysosome).

  
• Summarise innate immunity.

  Adaptive immunity takes over if the innate immunity is not able to destroy the germs.

  
• How do you connect innate with adaptive immunity?

  Dendritic cell (antigen presenting cell)

  These are present in blood & tissues, they capture the microbe and take it to lymph node to induce adaptive immunity
• What is a dendritic cell called in the skin?

  Langerhans cell
• Give an overview of the bridging of innate & adaptive immunity.

  
• What is adaptive immunity restricted to and mediated by?

  Restricted to vertebrates & mediated by lymphocytes:

  T cells- helper & cytotoxic

  B cells- antibody

  
• What is processing?

  When the dendritic cells digest the microbes into small peptide fragments
• How are antigens presented?

  1 of 2 ways:

  
  

  As MHC Class 1 molecules (internal pathogens, viral) or

  MHC Class 2 molecules (external pathogens, bacteria)
• What happens to the MHC/peptide complex?

  They're taken to the surface & presented to 1 of 2 T cells:

  If they're MHC Class 1- presented to CD8 +ve T cell (cytotoxic T cell)

  If they're MHC Class 2- presented to CD4 +ve T cell (T helper cell)
• What happens after CD4 +ve T cell activation?

  CD4 T cell doesnt directly kill but helps other cells to do so

  
  

  1. Proliferation

  2.Differentiation into effectors

  3.Different effector functions

  
• What are the areas of the lymph node?

  Dendritic cells enter through afferent lymphatic vessel and go to the paracortical area (where most T cells are activated)

  
• What is the general structure of an antibody?

  Variable region is specific to antigen that binds

  
• describe the timeline of adaptive immune response:

  
• What is the mechanism of T cell killing?

  Cytotoxic T cell recognises complex of viral peptide with MHC Class 1 & kills infected cell
• What happens when things go wrong in the immune system?

  Microbes are too clever and can hide inside cells

  Cancers can grow unchecked

  Harmless substances can be deemed dangerous

  Immune system can attack itself

  
• Describe the difference between innate and adaptive immunity:

  INNATE IMMUNITY IS CRUCIAL FOR ACTIVATION OF ADAPTIVE IMMUNITY

  
• What are the 2 main signalling molecules?

  Chemokines - attract cells to the site of infection

  Cytokines- induce function of immune cells

  
  

  Both are involved in adaptive and innate immunity
• What are lymphocytes?

  -Type of white blood cell

  -Adaptive immunity

  -Main types : T cells, B cells, NK cells
• What are granulocytes?

  -Type of white blood cell

  -Characterised by granules in their cytoplasm

  -Innate immune system

  
  

  E.g: neutrophils, basophils, eosinophils
• What are myeloid cells?

  -Originate from bone marrow

  
  

  E.g macrophages and dendritic cells
• What are the differences and similarities between the adaptive and innate immune system?