Immunity, antibodies, and monoclonal antibodies

Question 1

What is an antigen?

Answer 1

a protein located on the surface of cells that triggers the immune response

Question 2

What is a pathogen?

Answer 2

a microorganism that causes disease

Question 3

What are the four types of pathogens?

Answer 3

-bacteria
-virus
-fungi
-protist

Question 4

What are antigens made of?

Answer 4

they’re large complex proteins/chemical markers

Question 5

Where are different antigens found?

Answer 5

-on the surface of pathogens
-on the surface of abnormal cells (like cancer)
-on the surface of cells from other organisms in the same species
-on toxins produced by microorganisms

Question 6

What are examples of the first line of defence?

Answer 6

physical barrier- skin
chemical barrier- stomach acid

Question 7

What are examples of the second line of defence?

Answer 7

-inflammation
-blood clot
-phagocytosis

Question 8

What is the blood made up of?

Answer 8

55% plasma, 45% red blood cells, <1% white blood cells and platelets

Question 9

What are the two (broad) types of white blood cells?

Answer 9

phagocytes
lymphocytes

Question 10

What are the two types responses in the specific immune response?

Answer 10

cellular- T lymphocytes
humoral- B lymphocytes

Question 11

What do phagocytes do?

Answer 11

they are part of the non-specific, immediate response and they travel in the blood to the site of infection/trauma

Question 12

How do phagocytes deal with pathogens?

Answer 12

by the process of phagocytosis

Question 13

Explain the process of phagocytosis

Answer 13

pathogens release chemicals/debris that attract the phagocyte towards it along a concentration gradient via chemotaxis

the phagocyte has several receptors on it’s cell surface that attach to the pathogen

the phagocyte then engulfs the pathogen, making a phagosome

the lysosomes inside the phagocyte bind to the phagosome, creating a phagolysosome

the enzymes released (lysozymes) hydrolyse the pathogen which destroys it

Question 14

What do lymphocytes do?

Answer 14

they are involved in the specific immune response, and result in immunity, although their response is slower but more long term

Question 15

Give two differences between specific and non-specific immune responses

Answer 15

ns- same process for all pathogens
s- specific pathogens

ns- immediate response
s- longer process

Question 16

What is an antigen presenting cell?

Answer 16

any cell that presents a non-self antigen on it’s surface

Question 17

What is antigen variability?

Answer 17

the antigen on a pathogen changes frequently due to genetic mutations

Question 18

Why is antigen variability a problem for the immune system?

Answer 18

our immune system produces a specific immune response due to it’s memory cells- the lymphocytes and memory cells are complementary in shape to only one antigen, which means they can no longer bind if the antigen changes shape due to mutations. this means that there is no secondary immune response and the host gets infected and suffers symptoms of the disease again

Question 19

Where are phagocytes produced and stored?

Answer 19

in the bone marrow

Question 20

Where do phagocytes do their job?

Answer 20

in the blood

Question 21

What are the two types of phagocyte?

Answer 21

neutrophil/macrophage

Question 22

Where are lymphocytes produced and matured?

Answer 22

produced in the bone marrow and mature in the thymus

Question 23

How many different types of lymphocytes exist in your body?

Answer 23

around 10 million

Question 24

Why is infection in the foetus rare?

Answer 24

it is protected by the mother and the placenta

Question 25

What happens with the lymphocytes in a foetus?

Answer 25

infection is rare in a foetus so the lymphocytes collide almost exclusively with self cells, and some lymphocytes will have receptors that are complementary to the body's own cells, and these lymphocytes either die or are supressed the lymphocytes that remain only have receptors complementary to non-self cells

Question 26

Which cells are involved in the humoral response and why?

Answer 26

B-cells as they deal with immunity involving pathogens in bodily fluids

Question 27

Which cells are involved in the cell mediated response and why?

Answer 27

T-cells as they deal with immunity involving body cells

Question 28

Explain the cell mediated response

Answer 28

pathogens invade the body or are taken in by phagocytes the phagocytes present the antigens from the pathogen on its cell membrane receptors on a specific T helper cell are complementary to these antigens this attachment activates the T cell to divide rapidly by mitosis to form genetically identical clones the cloned T cells then: -develop into memory cells -stimulate phagocytes to engulf pathogens by phagocytosis -stimulate B cells to divide and secrete their antibody -activate cytotoxic killer T cells

Question 29

What do memory cells do?

Answer 29

enable a rapid response to future infections by the same pathogen (after a pathogen is dealt with some lymphocytes remain in the blood)

Question 30

How do cytotoxic killer T cells kill infected cells?

Answer 30

they produce a protein called perforin which makes holes in the cell surface membrane, making it become freely permeable to all substances, causing the cell to die

Question 31

What are 2 differences between T cells and B cells?

Answer 31

1- T cells mature in the thymus and B cells mature in the bone marrow 2- T cells are involved in cell mediated immunity and B cells are involved in humoral immunity

Question 32

Explain the humoral response

Answer 32

the antigens of an invading pathogen are taken up by a B-cell the B cell processes the antigens and presents them on its surface helper T cells attach to the antigens presented on the B cell which activates the B cell this makes the B cell divide by mitosis to give clones of plasma cells the plasma cells produce and secrete the specific antibody that is complementary to the pathogen's antigen these antibodies then bind to 2 pathogens causing agglutination phagocytes can then engulf and destroy the pathogens some B cells develop into memory cells also that can divide rapidly to produce a secondary immune response if the same pathogen infects again

Question 33

What are antibodies?

Answer 33

a protein that a B cell secretes in response to a non-self antigen

Question 34

What type of structure do antibodies have?

Answer 34

a quaternary structure

Question 35

How many polypeptide chains do antibodies have and what are they called?

Answer 35

they have 4 polypeptide chains and the longer ones are heavy chains whereas the shorter ones are light chains

Question 36

Where is the binding site on the antibody?

Answer 36

in the variable region

Question 37

How is the binding site unique on each antibody?

Answer 37

because each binding site consists of a unique sequence of amino acids that forms a specific 3D tertiary shape/binding site

Question 38

How can monoclonal antibodies be used for treating cancer?

Answer 38

direct monoclonal antibody therapy- MABs are produced that are specific to the antigens on the cancer cells these are then given to the patient and can attach themselves to the cancer cells' receptors by attaching to the cancer cells' surface they block the chemical signals that stimulate their uncontrolled growth indirect monoclonal antibody therapy- involves attaching cytotoxic/radioactive chemicals to the MABs that when they attach to the cancer cells they kill them

Question 39

How can monoclonal antibodies be used in medical diagnosis?

Answer 39

they can produce specific antibodies that will bind to a specific antigen, and also use dye, so that if the antigen you are testing for is present then the dye will show up. ELISA tests are often used

Question 40

Explain the problems to do with ethics within the use of monoclonal antibodies

Answer 40

production of MABs involves the use of mice although there has been many successes with using MABs to treat diseases like cancer/diabetes, there have been some deaths associated with their use in treating multiple sclerosis- patients should have informed consent

Question 41

What is clonal selection?

Answer 41

the process of matching the antigens on antigen presenting cells to the receptors on T and B lymphocytes

Question 42

What is the primary response?

Answer 42

after the 1st contact with an antigen, the time for the random collision of the complementary B cell to with the antigen, then the B cells divide to produce plasma and memory cells to deal with the pathogen

Question 43

What is the latent period?

Answer 43

the time from infection to antibody production

Question 44

What is the secondary response and how do we not show symptoms?

Answer 44

the 2nd exposure to the SAME pathogen, and it can be triggered by a smaller amount of antigen it is a more rapid response as the memory cells in the blood are more likely to collide with the antigen and bind to it, then the memory B cells start to divide to produce more plasma cells (hence more antibodies) the pathogen is therefore destroyed before it can fully infect- secondary response leads to more antibodies produced and faster