L63: Infection And Immunity

Question 1

Humoral response

Answer 1

Anything not related to cell

Innate: acute phase protein, complement, interferon (alpha, beta)
Specific: antibodies

Question 2

Cell-mediated response

Answer 2

Innate (T-independent): Neutrophils, Macrophages, NK cells (ADCC)
Specific (T-dependent): Cytotoxic T cell, Helper T cell (Th1 —> IL2, IFNgamma; Th2 —> IL4, IL10; Th17 —> IL17)

Question 3

Mechanism of cell killing by cytotoxic T cell and NK cell

Answer 3

Contain Fas ligand which bind to Fas receptor on target cell

Perforins: osmotic lysis, caspase + endonuclease activation —> apoptosis
Granzymes: caspase + endonuclease activation —> apoptosis

Question 4

Interferon

Answer 4

Innate: Type 1 (alpha/beta)
- alpha produced by virus-infected WBC
- beta produced by virus-infected fibroblast + epithelial cells
- induce anti-viral activities of cells
—> activate NK cells
—> enhance MHC Class I

Specific: Type II (gamma)
- produced by NK cell, Th1
- induce anti-viral activities of cells
—> activate macrophage
—> IL12 (cycle: activate Th1 —> IFNgamma —> activate macrophage —> IL12)
—> NO, enhance MHC I/II, direct killing of infected cells

Question 5

How phagocyte mediate killing

Answer 5

1. Oxygen intermediates (superoxide anions)
2. Nitrogen intermediates (nitric oxide)
3. Lysozyme (in lysosome), Prostaglandin
4. Cytokines (IL1, TNF, IFN)
5. Myeloperoxidase

Question 6

Immunodeficiencies

Answer 6

Primary (Intrinsic)

• genetic linked
• Severe combined immunodeficiency (lack T, B cells)

Secondary (Extrinsic)

• acquired
• AIDS, drugs, irradiation, malnutrition

Question 7

Recurrent vs opportunistic infections in immunodeficiency

Answer 7

Recurrent (pyogenic):

• no antibody, complement, phagocytes
• caused by encapsulated bacteria

Opportunistic:

• no cell-mediated immunity (lack T cells)
• caused by viruses, yeast

Question 8

Evidence of anti-tumour immunity

Answer 8

1. Adult’s tumour size is smaller than children’s/old-age’s
2. Immune cells infiltration in tumour
3. Spontaneous regression in tumour
4. Tumours larger in post-mortem
5. Graft versus leukaemia response

Question 9

Immune escape mechanism by tumours

Answer 9

1. Lack of immune molecules to surveillance

2. Tumour-derived factors suppress immunity

Question 10

Autoimmunity vs Immunological tolerance

Answer 10

Autoimmunity:
Adaptive immune response against self-antigens

Immunological tolerance:
A state of unresponsiveness to an antigen
- Ag specific
- Self-tolerance
- to foreign antigens (immunotherapy)