T Helper Cells And B Cells

Question 1

What do all cells have on their surface to identify and recognise them?

Answer 1

• specific molecules
• proteins/glycoproteins

Question 2

What do proteins and glycoproteins enable the immune system to identify?

Answer 2

• pathogens
• cells from other organisms of the same species
• abnormal body cells
• toxins

Question 3

Define what a pathogen is

Answer 3

Microorganism that causes disease and immune response

Question 4

What is an antigen?

Answer 4

A foreign protein that causes an immune response

Question 5

What are some examples of foreign bodies?

Answer 5

• proteins on pathogen
• infected body cells
• transplanted organ
• cancer cells

Question 6

What is antigenic variability?

Answer 6

Change of surface protein by microorganisms to evade the immune response

Question 7

What does antigenic variability affect?

Answer 7

Vaccine design and inability to control some infectious diseases

Question 8

Why do vaccines differ and are adapted each year?

Answer 8

Due to antigenic variability

Question 9

What does it mean for cells when antigenic variability takes place?

Answer 9

• change of surface protein means when infected for second time, memory cells produced from first infection won’t recognise different proteins
• immune system has to carry out primary response

Question 10

What is the affect of regular pathogens on cells?

Answer 10

• activates primary response
• when infected again with same pathogen,activates secondary response and memory cells are activated

Question 11

Describe the primary response

Answer 11

• when antigen enters body for first time and immune system is activated
• slow due to lack of B cells that produce antibodies
• infected person shows symptoms of disease
• T and B cells produce memory cells after being exposed to antigen

Question 12

What do memory T cells do?

Answer 12

Remember specific antigen and recognise second round

Question 13

What do memory B cells do?

Answer 13

Record specific antibodies needed to bind to the antigen

Question 14

Describe the secondary response

Answer 14

• clonal selection occurs faster
• memory B cells activated and divide by mitosis into plasma cells that produce antibodies
• memory T cell activated and divide into correct type to kill cell carrying antigen
• gets rid of pathogens before symptoms show

Question 15

What is an antibody?

Answer 15

A protein with specific binding sites complementary to specific antigen, synthesised and secreted by plasma cells

Question 16

What does the structure of the antibody include?

Answer 16

• constant region
• variable region
• disulphide bonds
• heavy chain
• light chain
• antigen binding sites

Question 17

What type of proteins are antibodies?

Answer 17

• Globular glycoproteins
• immunoglobulins

Question 18

How many polypeptide chains do antibodies contain?

Answer 18

4

Question 19

What is formed when antibody binds with an antigen?

Answer 19

Antigen antibody complex

Question 20

What are the effects of binding antigens and antibodies?

Answer 20

• tag/neutralise toxins
• agglutination (clumping of cells for easier phagocytosis)
• act as markers and signal phagocytes to engulf bacterial cells

Question 21

What type of cells are lymphocytes?

Answer 21

White blood cells

Question 22

Where do B lymphocytes mature?

Answer 22

Bone marrow

Question 23

What type of response are B lymphocytes associated with?

Answer 23

Humoral response

Question 24

Where do T lymphocytes mature in?

Answer 24

Thymus

Question 25

What type of response is T lymphocytes associated with?

Answer 25

Cell mediated (cellular) immunity

Question 26

What are antigen presenting cells?

Answer 26

Cells that display antigens that were on previous pathogen on the surface of the membrane

Question 27

What cells are antigen presenting?

Answer 27

• Phagocytes
• macrophages
• dendritic cells
• B cells

Question 28

What is the role of antigen presenting cells?

Answer 28

Present foreign antigens to helper T cells

Question 29

Describe the steps of cell mediated immune response

Answer 29

1. Macrophage engulfs microbe and carries out phagocytosis
2. Foreign antigens from microbe present itself on surface of macrophage and becomes antigen presenting cell
3. Helper T cell receptor binds to specific and complementary antigen on antigen presenting cell
4. Helper T cell undergoes clonal selection by mitosis and forms clone of genetically identical cells
   5, memory cells produced, cytokines released, cytotoxic T cells activated

Question 30

What do cytokines releasing do?

Answer 30

• Activate B cells to divide into plasma cells to produce and secrete specific antibodies

Question 31

Describe the steps of cytotoxic T cells attacking infected cells

Answer 31

1. Cytotoxic T cell bind to infected cell
2. Perforin makes holes in infected cell’s membrane and damages
3. Infected cell lyses

Question 32

Describe the steps of humoral immunity

Answer 32

1. Antigen is specific and complementary to antigen receptor on B cell
2. B cell processes antigen and presents them on its cell surface membrane (becomes antigen presenting cell)
3. Activated helper T cell attaches to processed antigens on B cell which activates B cell to release cytokines
4. B cell undergoes clonal selection by mitosis to give clone of plasma cells
5. Cloned plasma cells synthesise and secrete antibodies specific to antigen on surface of pathogen
6. Antibody attaches to specific and complementary antigens in pathogen and destroy them, also cause agglutination
7. Some B cells are memory cells

Question 33

State the differences in primary and secondary immune response

Answer 33

• occurs as a result of primary contact with antigen (pr), occurs as second and subsequent exposure to same antigen (sr)
• responding cell is naive B and T cell (pr), responding cell is memory cell
• antibody levels decline rapidly (pr), antibody levels remain high for longer (sr)