Immunology: Intro

Question 1

What makes up our immune system?

Answer 1

• Innate immune system
• Adaptive immune system
• Physical barriers

Question 2

What are the physical and chemical barriers against infection?

Answer 2

• Saliva
  
  • lysozyme, IgA, IgG, lactoferrin
• Mucociliary escalator
• Normal flora
• Physical flushing (urinary tract)

Question 3

What does the innate immune system do?

Answer 3

• Rapid
• Already present at birth
• Some specificity
• No memory – same response with re-exposure
• Detects alteration from haemostasis
  
  • Damage recognition - host
  • Pathogen recognition - pathogen

Question 4

Which cells make up the innate immune system?

Answer 4

• NK cells
• Mast cell
• Basophil
• Neutrophil
• Eosinophil
• Monocyte
• Macrophage
• Dendritic cell

Question 5

What are the mechanisms of innate immune system?

Answer 5

• Inflammation
• Recruitment of immune cells
• Activation of complement
• Opsonisation
• Phagocytosis
• NK cytotoxicity

Question 6

What is the role of cytokines?

Answer 6

• Regulate the nature, duration and intensity of the immune response
• Form a method of ‘communication’ between components of the immune system
• Bind to specific receptors on target cells
• Predominantly produced by macrophages and T helper cells
• Cytokines can cause cell growth and proliferation – increase leukocyte production

Question 7

During inflammation which cells detect the inflammation and what response do they cause?

Answer 7

Pattern recognition receptors (PRR)

• Vasodilation
• Increased vascular permeability
• Increased cell adhesion molecules
• Chemotaxis
• Increased sensitivity to pain

Question 8

Which molecules are related to vasodilation?

Answer 8

• Nitric oxide
• Bradykinin
• Prostaglandins
• TNF alpha

Question 9

Which molecules increases sensitivity to pain?

Answer 9

Bradykinin

Question 10

Increased vascular permeability?

Answer 10

Histamine, Nitric oxide

Question 11

What are the roles of complement?

Answer 11

1. Chemotaxis of phagocytes to sites of inflammation
   - (C3a, C5a)
2. Opsonisation
   - (C3b, C4b)
3. Lysis of micro-organisms
   - (C5b-9 complex)
4. Maintain solubility of Ag / Ab complexes

Question 12

What is opsonisation?

Answer 12

Prepare for eating by phagocytosis

Main opsonins:

–Complement C3b, C4b

–Antibodies

–Plasma proteins – mannose binding lectin

Question 13

What are the features of the adaptive immune system?

Answer 13

• Specific
• Delayed
• Immunological memory
  
  • Faster responses to known antigen
• 1. Humoral
     * Antibody-mediated
     * B lymphocytes
• 2. Cell-mediated
     * T lymphocytes

Question 14

Where do lymphocytes mature?

Answer 14

T cells - thymus

B cells - bone marrow

• B and T cells then migrate to secondary lymphoid organs, where they encounter antigen

Question 15

What is an antibody?

Answer 15

• A glycoprotein produced by B lymphocytes that binds antigens with a high degree of specificity and affinity

Question 16

Which cells bind to MHC-1 and what pathogens do they show?

Answer 16

• CD8+ cells bind to MHC-1
• MHC-1 are normal receptors and show intracellular pathogens (virus)

Question 17

WHich cells bind to MHC-II and what pathogens do they express?

Answer 17

MHC-II are professional cells (dendritic, macrophages, B lymphocytes) - CD4+ helper cells bind, they cells who extracellular pathogens.

Question 18

What is central tolerance?

Answer 18

• Occurs in the primary lymphoid organs
• Thymus and bone marrow
• Make sure that immune cells are not self reactive

Positive selection – can T cells recognise MHC?

Negative selection – does T cell interact too strongly with self antigens via MHC?

Question 19

What is peripheral tolerance?

Answer 19

• Occurs in the secondary lymphoid organs
• Regulates mature cells
• Monitoring of lymphocytes within secondary lymphoid organs and circulation

Regulatory T cells – recognise and destroy self-reactive lymphocytes

Question 20

What do cytoxic CD8+ cells release?

Answer 20

• Release IFN-g and TNF-a
  
  • Direct anti-viral and anti-tumour effects
• Release cytotoxic granules:
  
  • Perforin + granzyme = apoptosis of target cell

Question 21

What do CD4+ cells release/do?

Answer 21

• Release cytokines to ‘help’ the activity of other immune cells
• Promote B cell antibody class switching

Question 22

What are the functions of an antibody?

Answer 22

1. Immune complex formation
2. Opsonisation
3. Activating the cascade complement
4. Antibody-dependent cellular cytotoxicity (ADCC)
   
   1. Bind to target cells and initiate a non- phagocytic cell-mediated destruction

Question 23

What are some secondary causes of immune deficiency?

Answer 23

• Environmental
• Disease
• Iatrogenic

Question 24

Summary of functions of innate immune system:

Answer 24

• Endothelial cells, Macrophages and dendritic cells
  
  • Recognise virus via PRRs
  • Release cytokines and IFN: direct antiviral effect
• Chemotaxis
• Phagocytosis: macrophages, neutrophils, dendritic cells
• NK cell cytotoxicity
• Complement activation
  
  • viral aggregation and coating. Lysis of virally infected cells
• Opsonisation

Question 25

Summary of function of adaptive immune system:

Answer 25

* Presentation of antigen to lymphocytes in lymph nodes * Infected dendritice cell presents via MHC I * Phagocytic dendritic cell presents via MHC II * T lymphocytes * CD8+ cytotoxic T cells * TNF-alpha and IFN rlease * Perforin and granzyme-mediated apoptosis * CD4+ esp: Th1 * IFN release * Maximise macrophage and Tc activity * B cell activation, differntiation and class switching