Specific Immune System

Question 1

Compare specific defence mechanisms to non-specific defence mechanisms?

Answer 1

• Specific defence mechanisms are slower
• Produce a unique response to each type of pathogen
• Provide long-term immunity against specific pathogens

Question 2

Type of specific responses?

Answer 2

• Cellular
• Humoral

Question 3

Two types of lymphocyte:

Answer 3

• T lymphocytes / T cells –> mature in the thymus gland. They are involved in the cellular response where they respond to antigens presented on body cells
• B lymphocytes or B cells –> B cells mature in the bone marrow. They are involved in the hormonal response and produce antibodies found in body fluids or humours.

Question 4

Types of T cells:

Answer 4

• T helper cells
• T killer cells
• T regulator cells
• T memory cells

Question 5

T helper cells

Answer 5

• Receptors on cell-surface that bind to complementary antigens on antigen-presenting cells.
• Produce interleukins (a types of cytokine) which stimulate B cells or phagocytes
• T helper cells can also form memory cells or T killer cells

Question 6

T killer cells

Answer 6

• Kill abnormal or foreign cells by producing a protein known as perforin.
• This protein makes holes in the cell-surface membrane, causing it to become freely permeable and causing cell death.

Question 7

T regulator cells

Answer 7

• These cells suppress the immune system after pathogens have been destroyed.
• This stops the immune system from mistakenly attacking body cells

Question 8

T memory cells:

Answer 8

• Provide long-term immunity against specific pathogens.
• They provide rapid response if the body is re-infected by the same pathogen

Question 9

Why is the cellular response called the cellular response:

Answer 9

• T cells will only respond to antigens presented on body cells rather than antigens within body fluid.

Question 10

Stages of the cellular response:

Answer 10

• Macrophages engulf pathogens and display their antigens on the cell-surface. These are known as antigen-presenting cells
• T helper cells with complementary receptors bind to these antigens
• On binding, the T helper cell is activated to divide by mitosis to form genetically identical clones

Question 11

Cloned T cells functions:

Answer 11

• Develop into memory cells –> circulate body to provide long-term immunity.
• Develop into T killer cells –> destroy infected cells
• Stimulate phagocytosis –> cells produce interleukins, stimulating phagocytes to engulf pathogens
• Stimulate division of B cells –> cells produce interleukins, which stimulate B cells to divide and produce antibodies.

Question 12

Humoral response explanation:

Answer 12

• Use of B lymphocytes or B cells.
• Produce and are covered in proteins known as antibodies.
• It is called the humoral response as antibodies are found in body fluids which are known as humors

Question 13

Cells involved in the humoral response:

Answer 13

• B cells
• Plasma cells
• Memory cells
• T helper cells

Question 14

B cells: humoral response

Answer 14

• Antibodies on cell surface membrane that bind to complementary antigens.
• Engulf the antigens and display them on their cell-surface to become antigen-presenting cells.
• Once activated, B cells can divide into plasma cells and memory cells.

Question 15

Plasma cells: humoral response

Answer 15

• Types of B cells that can produce and secrete antibodies against specific antigen.
• Short lifespan –> a few days

Question 16

Memory cells: humoral response

Answer 16

• Types of B cell that provide long-term immunity against specific pathogens.
• Longer lifespan than plasma cells
• Rapidly divide into plasma cells if the body is re-infected by same pathogen.

Question 17

T helper cells: humoral

Answer 17

• Bind to antigen-presenting cells to activate division of B cells

Question 18

Stages of humoral response:

Answer 18

• A B cell with a complementary antibody binds to the antigens on a pathogen
• B cell engulfs the pathogen and presents its antigens on the cell-surface membrane to become an antigen-presenting cell.
• Clonal selection –> Activated T helper cells bind to the B cell, causing activation of this B cell
• Clonal expansion –> Activated B cell divides by mitosis to form plasma and memory clones
• Cloned plasma cells produce and secrete specific antibody which is complementary to the antigen on the pathogen’s surface. These antibodies attach to antigens on pathogens and destroy them.
• The memory cells circulate the blood and tissue fluid, ready to divide if the body is re-infected by the same pathogen

Question 19

Clonal selection:

Answer 19

The B cell with the correct antibody is selected for cloning (by being activated by a T helper cell)

Question 20

Clonal expansion

Answer 20

The division of specific B cells to produce genetically identical clones

Question 21

Primary immune response:

Answer 21

• Takes place when the body is exposed to the pathogen for the first time. This response is slow and the infected individual experiences symptoms of the disease.

Question 22

Secondary immune response:

Answer 22

• This takes place when the body has been exposed to the same pathogen before. This response is much faster and stronger and pathogens are destroyed before any symptoms appear.

Question 23

Explanation of primary immune response:

Answer 23

1. Production of antibodies is slow after exposure to the pathogen (longer lag phase)
2. The concentration of antibodies increases slowly
3. Few B cells that are specific to the pathogen’s antigens
4. Takes time for the B cells to divide into plasma cells to produce the correct antibody.
5. During this process, some B cells divide into memory cells to make the individual immune to this disease

Question 24

Secondary immune response:

Answer 24

1. The production of antibodies is much quicker after exposure to the pathogen (shorter lag phase)
2. The concentration of antibodies increases quickly.
3. This is because memory B cells recognise the pathogen’s antigens and quickly divide into plasma cells.
4. These plasma cells secrete larger numbers of antibodies to quickly destroy the pathogen before the individual experiences any symptoms.
5. Memory T cells are also activated to divide into T killer cells to destroy the pathogen.

Question 25

Compare: exposure to pathogen

Answer 25

Primary --> first Secondary --> second / later

Question 26

Compare: speed of response

Answer 26

P --> Slow S --> Fast

Question 27

Compare: symptoms

Answer 27

P --> Yes S --> No

Question 28

Compare: cells activated

Answer 28

P --> B and T cells S --> Memory B and T cells

Question 29

Compare: Rate of antibody production

Answer 29

P --> Low S --> High

Question 30

Compare: Number of antibodies produced

Answer 30

P --> Low S --> High

Question 31

Compare: Number of antibodies produced

Answer 31

P --> few S --> large numbers

Question 32

Compare: time between pathogen exposure and antibody production

Answer 32

P --> long (4-7 days) S --> short (1-3 days)

Question 33

Autoimmune disease

Answer 33

The immune system cannot recognise self antigens and starts to attack them

Question 34

Examples of autoimmune diseases:

Answer 34

- Type 1 diabetes --> The immune system attacks the insulin-secreting cells of the pancreas, causing a lack of insulin. - Lupus --> The immune system attacks cells in the connective tissues, causing inflammation. - Rheumatoid arthritis --> The immune system attacks cells in the joints, causing pain and inflammation.