ADAPTIVE IMMUNITY

Question 1

How do T cells recognize an infected cell or foreign protein ag?

Answer 1

• Ag are broken down into smaller fragments
• then they will interact with MHC class I or II molecules
• the peptide-MHC complex molecules moves to the surface of the cell so it can be recognised by the T cells
• T cells is then activated and elicit an immune response

Question 2

What MHC class I,II and III encodes for?

Answer 2

MHC class I- HLA- A, HLA- B, HLA- C
MHC class II- HLA- DP, HLA-DQ, HLA-DR
MHC class III- encodes for complement proteins and cytokines

Question 3

Who recognized MHC class I and MHC class II?

Answer 3

MHC class I is recognised by the CD8 positive cytotoxic T cell
MHC class II is recognised by the CD4 positive helper T cell

Question 4

Where does MHC class I and class II distritubed?

Answer 4

MHC class I is distributed to most nucleated somatic cells, except cells of the brain and retina
MHC class II is distributed to APC (macrophages, dendritic cells, B cells) and IFN- y activated cells

Question 5

What does humoral immunity (antibody- mediated immunity) againt to?

Answer 5

1. Exotoxin mediated disease (tetanus and diphtheria)
2. Infections in which virulence is against polysaccharide capsule (S. pneumoniae)
3. Viral infections (influenza virus)

Question 6

How does the B cells activated and what is the outcome?

Answer 6

The B cell is activated with the help from the helper T cells.
The outcome from the activated B cells are:
1. Ab is produced.
2. Isotype switching
3. Affinity maturation
4. Memory B cell production

Question 7

State 4 difference between primary immune response and secondary immune response.

Answer 7

Primary immune response:
1. Naive B cells is involved
2. Time lag after B cell encounter the ag are 5-10 days
3. Peak response is smaller
4. The highest ab is IgM

Secondary immune response:
1. Memory B cells is involved
2. Time lag after B cell encounter the ag are 1- 3 days
3. Peak response is larger
4. The highest ab is IgG.

Question 8

State the function of antibodies.

Answer 8

To protect against infectious agent by neutralising the toxins and viruses and opsonize the microbes

Question 9

What happen to the ab in the foetus and infants?

Answer 9

In foetus:
Its ab is obtained from the mother through the placenta (passive immunity) which occur during the third trimester of pregnancy.
Its ab is primarily IgG.

In infants:
It immunity is short lived during the first 6 month of life and the maternal IgG are declined.
The newborn now can make its own ab (IgG) to certain proteins such as against Hep B surface ag.

Others:
Colostrum and breast milk have IgA.

Question 10

What lab test we can used to observe ab?

Answer 10

ELISA and Haemagglutination inhibition (
HI)

Question 11

What cell primarily used in cell mediated immunity?

Answer 11

T cells (Cytotoxic T cells and helper T cells)

Question 12

What is the f(x) of Cytotoxic T cells and Helper T cells?

Answer 12

Cytotoxic T cells: kill the virus-infected cells
Helper T cells: Ag recognition and produce cytokines

Question 13

What is the f(x) of cell mediated immunity?

Answer 13

1. To defense against infections of fungi, parasites and certain intracellular bacteria.
2. To kills virus- infected cells and tumour cells
3. Rejection of organ transplant

Question 14

State 4 examples of CMI reaction

Answer 14

1. Tuberculin test
2. Anti viral immunity
3. Killing intracellular parasites
4. Graft rejection
5. Gract- versus- host disease
6. Contact sensitivity
   (any 4)

Question 15

What is the role of adjuvant and lipis in establishing CMI?

Answer 15

To enhance uptake of ag by APC by:
1. stimulating the expression of co- stimulators
2. enhancing the production of cytokines (IL-12)
3. promoting the development of T- helper 1 cells

Question 16

What is the difference between active immunity and passive immunity in immunization?

Answer 16

Active immunity: induced after contact with foreign ag.
Passive immunity: induced after administered preformedantibodes