Specific immune responses

Question 1

What are the 2 types of lymphocytes?

Answer 1

• T lymphocytes
• B lymphocytes

Question 2

What are T lymphocytes and where do they mature?

Answer 2

Involved in cellular response where they respond to antigens presented on body cells

mature in thymus gland

Question 3

What are B lymphocytes and where do they mature?

Answer 3

Involved in humoral response where they produce antibodies found in body fluids

mature in bone marrow

Question 4

What are the 4 types of T cells?

Answer 4

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

Question 5

What are the functions of T helper cells?

Answer 5

• receptors on cell-surface that bind to complementary antigens on antigen-presenting cells
• produce interleukins (cytokine type) stimulate B cells or phagocytes
• cells can also form memory cells or T killer cells

Question 6

What are the function of T killer cells?

Answer 6

Kill abnormal and foreign cells by producing a protein (perforin) which makes holes in cell-surface membrane causing it to become freely permeable causing cell death

Question 7

What is the function of T regulator cells?

Answer 7

Suppress immune system after pathogens have been destroyed helping to prevent immune system from mistakenly attacking body cells

Question 8

What is the function of T memory cells?

Answer 8

Provide long-term immunity against specific pathogens and provide rapid response if re-infected by same pathogen

Question 9

Why does the cellular response have it’s name?

Answer 9

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

Question 10

Outline the stages of the cellular response?

Answer 10

1) macrophages engulf pathogens displaying antigens on cell-surface (antigen-presenting cells)

2) T helper cells with complementary receptors bind to antigens

3) on binding T helper cells activated to divide by mitosis forming genetically identical clones

Question 11

What function can cloned T cells carry out?

Answer 11

Develop into memory cells = circulate in body providing long-term immunity

Develop into T killer cells = destroying infected cells

Stimulate phagocytosis = cells produce interleukins which stimulate phagocytes to engulf pathogens

Stimulate B cell division = cells produce interleukins which stimulate B cells to divide and produce antibodies

Question 12

What is the humoral response?

Answer 12

Specific defence mechanisms protecting body from disease by producing specific antibodies to destroy pathogens

Question 13

Why does the humoral response have it’s name?

Answer 13

B cells produce and are covered in proteins known as antibodies which are found in body fluids (humors)

Question 14

What are the cells involved in the humoral respose?

Answer 14

• B cells
• plasma cells
• memory cells
• helper T cells

Question 15

What is the function of B cells?

Answer 15

1) cells have antibodies on cell-surface membrane that bind to complementary antigens

2) they engulf antigens and display them on cell-surface to become antigen-presenting cells

3) once activated B cells can divide into plasma cells and memory cells

Question 16

What is the function of plasma cells?

Answer 16

Types of B cell that can produce and secrete antibodies against a specific antigen and have a short lifespan of only a few day

Question 17

What is the function of memory cells?

Answer 17

• provide long-term immunity against specific pathogens
• have much longer lifespan than plasma cells
• rapidly divide into plasma cells if body is re-infected by the same pathogen

Question 18

Outline the stages of the humoral response?

Answer 18

1) B cell with complementary antibody binds to antigens on pathogen

2) B cell engulfs pathogen and presents its antigens on the cell-surface membrane (antigen-presenting cell)

3) activated T helper cells bind to B cells activating them

4) activated B cell divides by mitosis to form plasma and memory cell clones

5) cloned plasma cells secrete specific antibody which is complementary to antigen on pathogen’s surface destroying the pathogen

6) memory cells circulate blood and tissue fluid ready to divide if body is re-infected by same pathogen

Question 19

What is clonal selection?

Answer 19

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

Question 20

What is clonal expansion?

Answer 20

Division of specific B cells to produce genetically identical clones

Question 21

What is the primary immune response?

Answer 21

Takes place when body is exposed to pathogen for first time so response is slow so infected individual experiences symptoms of disease

Question 22

What is the secondary immune response?

Answer 22

Takes place when body’s been exposed to same pathogen before so response is much faster and stronger destroying pathogens before any symptoms appear

Question 23

Describe the primary immune response?

Answer 23

• antibody production is slow after exposure to pathogen (longer lag phase)
• concentration of antibodies increases slowly due to few B cells specific to pathogen’s antigens
• takes time for B cells to divide into plasma cells to produce correct antibody (symptoms experienced)
• during process some B cells divide into memory cells to make individual immune to disease

Question 24

Describe the secondary immune response?

Answer 24

• antibody production is much quicker after exposure to pathogen (shorter lag phase)
• concentration of antibodies increases quickly due to memory B cells recognising pathogen’s antigens and quickly divide into plasma cells
• plasma cells secrete larger antibody number quickly destroying pathogen before individual experiences any symptoms
• memory T cells also activated to divide into T killer cells to destroy pathogen

Question 25

What is an autoimmune disease?

Answer 25

Immune system can't recognise 'self' antigens and starts to attack them breaking down healthy tissues

Question 26

What are some examples of autoimmune diseases?

Answer 26

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

Question 27

What are antibodies?

Answer 27

Y-shaped glycoproteins made up of 4 polypeptide chains 2 heavy chains and 2 light chains

Question 28

What are the regions of an antibody?

Answer 28

Constant region = same for all antibodies and binds to receptors on cells (e.g B cells) Variable region = different for each antibody as its shape is complementary specific antigen so is where the antigen binds Hinge region = allows antibody to be flexible so it can bind to multiple antigens at once

Question 29

What happens when an antigen binds to an antibody?

Answer 29

Forms an antigen-antibody complex

Question 30

What are 3 roles of antibodies to help destroy pathogens?

Answer 30

Pathogen agglutination = clumping pathogens together to enable easier phagocytosis Toxin neutralisation = antibodies bind to toxins inactivating them Preventing pathogen binding = antibodies bind to pathogens to stop them from infecting body cells

Question 31

How do antibodies act as agglutinins and opsonin's?

Answer 31

Agglutinins = make it easier for phagocytes to locate pathogens and engulf a number of pathogens at once Opsonin's = make pathogens easily recognisable by phagocytes

Question 32

How do antibodies bind to antitoxins?

Answer 32

Bind to toxins produced by pathogens neutralising (inactivating) toxins preventing them from damaging cells

Question 33

How do antibodies prevent pathogen cell binding?

Answer 33

Bind to pathogen's antigens so block cell-surface receptors needed to bind to host cells so pathogen can't bind to host cells