The Immune System

Question 1

What is a pathogen?

Answer 1

An organism that causes communicable disease by destroying cells or secreting toxins

Question 2

What is an antigen?

Answer 2

A protein on the cell membrane which initiates an immune response

Question 3

What is cellular immune response?

Answer 3

1. White blood cells (lymphocytes) destroy pathogens or toxins directly
2. (Phagocytes / Killer T-cells)

Question 4

What is the humoral immune response?

Answer 4

1. Antibodies destroy pathogens or toxins
2. B-cells and Plasma cells

Question 5

Describe the non-specific immune response of a white blood cell.

Answer 5

1. Phagocyte recognises foreign antigen on pathogen
2. Phagocyte engulfs pathogen into a phagosome
3. Lysosomes fuse with the phagosome
4. Lysozymes are releases which hydrolyse the pathogen

Question 6

Describe specific immune response of a white blood cell.

Answer 6

1. Phagocyte presents the pathogens antigen on its cell surface membrane
2. Phagocytes are antigen presenting cells
3. T-helper cell with complementary receptor binds to the presented antigen
4. This activates complementary T-killer and B-lymphocytes
5. By releasing cell signaling molecules
   -e.g. cytokines

Question 7

What activates T-cells?

Answer 7

1. Activated by antigens presented by phagocytes

Question 8

What are the 2 types of T-Cells?

Answer 8

1. T-Helper Cells -> activate B-Cells / Cytotoxic T-Cells
2. Cytotoxic T-Cells -> kill pathogens (Cellular response)

Question 9

What is an antibody?

Answer 9

Proteins that bind to antigens to kill pathogens

Question 10

What is clonal selection?

Answer 10

Only the B-Cell that forms an antigen-antibody complex is selected to divide into plasma cells

Question 11

What do B-Cells do?

Answer 11

1. The B-Cells with the complementary antibody forms an antigen-antibody complex and activates the right B-Cell
2. Selected B-cell divides / clones itself -> many copies called plasma cells

Question 12

What are plasma cells?

Answer 12

1. Clones of the selected B-Cell with complementary antibody to pathogens antigen

Question 13

What is the purpose of plasma cells?

Answer 13

1. Make monoclonal antibodies -> antigen - antibody complex with antigen
2. Stick pathogens together = agglutination
3. Phagocytes can destroy many pathogens at once
4. When infection is over. Plasma cells are saved as memory B-Cells

Question 14

What is the structure of an antibody?

Answer 14

1. Y shaped protein with a quaternary structure
2. Constant region is the same for all antibodies
3. Variable region is specific and only complementary to one antigen

Question 15

What is agglutination?

Answer 15

Attaching of multiple proteins to form a clump

Question 16

What is the benefit of the agglutination of phagocytes?

Answer 16

Many pathogens can be destroyed at once by a single phagocyte

Question 17

What is the primary immune response?

Answer 17

1. First immune response to a pathogen
2. Longer lag time
   - No memory cells
3. Clonal selection
4. Pathogens multiply and damage host cells
5. T-Cells and B-Cells become memory cells

Question 18

What is the secondary immune response?

Answer 18

1. Second infection by some pathogen / antigen
2. Shorter lag time
3. More antibodies produced
4. Rate of antibody production is faster
5. You will not feel symptoms

Question 19

What is a monoclonal antibody?

Answer 19

Identical antibodies made from the same B-Cell / Plasma Cell

Question 20

How are monoclonal antibodies used to deliver drugs?

Answer 20

1. All cells have different / specific antigens on their surface
2. Attach drugs to antibodies -> bind to target cells
3. Drug + Antibody will only bind to target cells

Question 21

What is a vaccine?

Answer 21

Contains antigens / antigenic material (dead / weakened pathogens) to stimulate an immune response

Question 22

What is active immunity?

Answer 22

When you make your own antibodies

Question 23

What is Natural active immunity?

Answer 23

Antibodies made after exposure to a pathogen

Question 24

What is artificial active immunity?

Answer 24

Antibodies made after a vaccination

Question 25

What is passive immunity?

Answer 25

When you are given antibodies by another organism

Question 26

What is natural passive immunity?

Answer 26

Antibodies transmitted from mother to baby via placenta or breast milk

Question 27

What is artificial passive immunity?

Answer 27

Antibodies are acquired from a blood transfusion or immune serum medicine

Question 28

What is an ELISA test?

Answer 28

Enzyme Linked Immuno Solvent Assay

Question 29

Describe the Direct test for antigens?

Answer 29

1. Immobilised antibodies are attached to well 2. Sample added 3. 4 Blood Plasma contains antigen - form antigen - antibody complex 4. Rinse to remove unbound antigens 5. Antibody + enzyme is added 6. Rinse to remove the unbound antibodies 7. Add substrate -> if it's positive -> colour change

Question 30

Describe the indirect test for antibodies?

Answer 30

1. Antigen is fixed to the well 2. A sample is added -> if complementary it will form an antigen - antibody complex 3. Rinsed to remove unbound antibodies 4. A different antibody is added with an enzyme attached 5. Rinsed to remove unbound antibodies + enzyme

Question 31

What does HIV do?

Answer 31

Infect Helper T-Cells and weakens the immune system

Question 32

How does HIV replicate?

Answer 32

1. Virus attachment protein binds to receptor on host 2. Reverse transcriptase -> makes double stranded DNA from RNA 3. DNA entered nucleus via nuclear port 4. TH-Cells makes more copies of the virus genetic material (RNA) + proteins (reverse transcription) 5. Reforms Capsid 6. Leaves host cell -> takes an envelope from hosts membrane