Immune Responses to Bacteria

Question 1

DEFENCES:
What are the Non-specific and Adaptive Natural barriers against bacteria?

What are the Non-specific and Adaptive Tissue and Blood defences against bacteria?

What molecules link the Innate to the Adaptive immune system?

What is Immune Exclusion?

What is Immune Elimination?

Answer 1

• • Non-specific - Skin, Shedding of skin, Flora, Bile, Lysozymes
  • Adaptive - Secretory IgA, Mucosa/Skin/Gut Associated Lymphoid tissue
• • Non-specific - Complement, Phagocytes, Neutrophils, Acute phase proteins
  • Adaptive - T cells, Antibodies
• PAMPs (Pathogen Associated Molecular Patterns) on pathogens are recognised by PRRs (Pattern Recognition Receptors) on cells
• Prior exposure to the foreign antigens causes Neutralisation of toxins and Prevention of adherence by antibody secretion
• Use of all defences when epithelium is damaged

Question 2

SERUM RESISTANCE:
How can Bacteria have a natural resistance to the Host’s non-specific, innate response? What does this lead to?

Since the non-specific, innate response is ineffective when the bacteria have resistance, what is required for the bacteria to be killed?
→ What can be given to promote this?

Answer 2

• Bacterial capsules (Sialic acid/Hyaluronic acid) and Lipopolysaccharides cause ↓Complement binding/activation = ↓Opsonisation and Phagocytosis
• Specific antibodies for opsonisation, phagocytosis and killing
  → Vaccines

Question 3

Give examples of Extracellular microbes. What is used in the extracellular immune response against these?

Give examples of Cytoplasmic microbes. What is used in the cytoplasmic immune response against these?

Give examples of Vaculoar microbes. What is used in the vacuolar immune response against these?

Answer 3

• e.g. S. aureus, S. pyogenes, E. coli
  • Complement
  • Antibodies
  • Phagocytosis
• e.g. Shigella, Listeria
  • Cytotoxic CD8 cells
  • NK cells
  • Antibody-dependent cell cytotoxicity
• e.g. TB, Salmonella, Yersinia
  • CD4 cells
  • Macrophages