2- Immune system

Question 1

What is an antigen

Answer 1

Molecules that cause an immune response

Question 2

What are phagocytes

Answer 2

-White blood cells that engulf pathogens and enclose them inside a membrane vesicle (phagosome)
-Lysosomes fuse with phagosomes releasing lysozymes which digest the pathogens molecules killing it
- Pathogens antigen is displayed on the surface

Question 3

What happens to antigen presenting cells

Answer 3

-Bind to complementary receptor proteins on specific helper T cell
- Activated Th cell releases cytokines which activate cytotoxic T cells and B cells which replicate by mitosis

Question 4

What do cytotoxic T cells do

Answer 4

-Detect antigens on infected body cells
- Release perforin- holes in cell membrane- lysis- cell bursts

Question 5

What do plasma cells (replicated B cells) do

Answer 5

-Make and release monoclonal antibodies- agglutinate pathogens by forming antibody-antigen complex - more effective phagocytosis

Question 6

Structure of antibody

Answer 6

• 4 polypeptide chains to form Y-shaped molecule
• 2 binding sites - each for a specific antigen

Question 7

What is vaccination

Answer 7

Preparation of antigen from a pathogen that will generate a primary immune response when injected

Question 8

Differences between active and passive immunity

Answer 8

Active-
-Requires exposure to the antigen
-Takes a while to develop protection (primary immune response has to take place)
-Memory cells are produced
- Protection is long term

Question 9

Structure of HIV

Answer 9

• Capsid- protein coat containing RNA and revere transcriptase enzyme
• Lipid envelope
• Antigen

Question 10

How does HIV replicate inside Th cells

Answer 10

• Antigens on virus bind to receptor proteins on T cell
  -HIVs lipid envelope fuses with T cell membrane releasing capsid out of cell
  -RNA and reverse transcriptase released into capsid which are used to make viral proteins- which are assembled to make viruses
• Virus leaves cell causing cell to rupture and die ad viruses go to infect other Th cells

Question 11

How does HIV cause AIDs

Answer 11

• Decreases T cell count in blood causing weakened immune system

Question 12

What are the steps in ELISA

Answer 12

1- Antigens stuck to bottom of well
2 - Sample (blood, urine) added to well - well is washed to remove any unbound antibodies
3 - Monoclonal antibodies with enzyme attached to bind to specific antibody - well is washed to remove unbound mAbs
4 - Substrate added binds to active site on enzyme on MAB forms an ES complex - when substrate is hydrolysed - colourless to blue