3.2.4 Cell Recognition and The Immune System

Question 1

How does the body identify ‘self cells’?

Answer 1

Each cell has specific molecules on the cell surface membrane to identify it

Question 2

How does the body identify ‘non-self’ cells?

Answer 2

Non-self cells contain antigens

Question 3

Where are antigens found from?

Answer 3

1. Pathogens
2. Transplanted cells
3. Abnormal body cells e.g., cancer cells
4. Toxins

Question 4

Antigens

Answer 4

A foreign molecule, usually a protein that stimulates an immune response in the production of a specific antibody

Question 5

If the body detects an antigen and recognises it as ‘non-self’, what will occur?

Answer 5

The body will initiate an immune response leading to destruction of cell/pathogen/protein

Question 6

2 other names for phagocytes

Answer 6

1. Neutrophil
2. Macrophage

Question 7

The objective of phagocytosis is to…

Answer 7

Destroy non-self pathogens

Question 8

Which type of process is phagocytosis?

Answer 8

Non-specific process

Question 9

Describe how phagocytosis occurs as an immune response within the body (6)

Answer 9

1. Chemical products of pathogens/dead/damaged/abnormal cells act as attractants
2. (Phagocytes) receptors (on the cell surface membrane) recognise and attach to chemicals on surface of pathogens
3. Pathogens engulfed to form vesicle
   Accept phagosome
4. Lysosome fuses with vesicle
5. Lysosome/hydrolytic enzymes break vesicle down
6. Debris/products/waste released out of the cell surface membrane
   Allow exocytosis

Question 10

State what is meant by antigen presentation (1)

Answer 10

After phagocytosis, phagocytes act as antigen presenting cells

Question 11

What does antigen presentation allow?

Answer 11

Activation of other imminence cells e.g., lymphocytes which mount a specific immune response to help remove the pathogen more efficiently

Question 12

How do lymphocytes bind to antigen being expressed in antigen presentation?

Answer 12

They have specific receptors complementary to the antigen being expressd

Question 13

Describe what is meant by non-specific immune responses (1)

Answer 13

A response no matter the pathogen, requires phagocytes to undergo phagocytosis

Question 14

Describe what is meant by specific immune responses (2)

Answer 14

1. Reacts to specific antigen of pathogen
2. Upon activation, many immune cells are produced providing a large and effective response

Question 15

Explain how specific immune responses aid in providing immunity upon reinfection (2)

Answer 15

2. This removes pathogen from body and creates immunity for the pathogen - memory cells are produced
3. Upon re infection, these cells initiate a larger and faster response

Question 16

Antigenic variability

Answer 16

When pathogens change antigen on surface during mutation (as they know they will die out)