cell recognition and the immune system

Question 1

define a pathogen

Answer 1

a microorganism that causes disease

Question 2

give 3 examples of a pathogen

Answer 2

• bacteria
• fungi
• viruses

Question 3

how do pathogens cause disease?

Answer 3

damaging host cells or realising toxins

Question 4

what is the immune system responsible for ?

Answer 4

resisting disease

Question 5

define an antigen

Answer 5

a protein (or glycoprotein) that can cause an immune response
antigen are often found on cell membranes (extrinsic proteins)

Question 6

what do antigens allow the immune system to identify?

Answer 6

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

Question 7

which immune system is present at birth?

Answer 7

the non-specific

Question 8

define phagocytosis

Answer 8

the term used to describe how a forgein substance such as a bacterium within a vesicle fuses with lysosomes in the cytoplasm

Question 9

lysosomes contain hydrolytic enzymes. what is the function of these?

Answer 9

digestive enzymes used to hydrolyse molecules e.g. proteins in pathogens or organelles

Question 10

give the sequence of phagocytosis

Answer 10

• phagocytes recognise and bind to the antigen on the pathogen
• phagocytes engulf pathogens
• they are enclosed in a vacuole/vesicle
• lysosomes fuse with the vesicle
• lysosomes contain lysozymes (hydrolytic enzymes that damage bacterial cell walls)
• these digest the pathogen, by hydrolysis of its molecules

Question 11

what is phagocytosis an example of ?

Answer 11

the non-specific immune response

Question 12

give two examples of a specific immune response

Answer 12

cellular response and humoral response

Question 13

what are the humoral and cellular responses examples of ?

Answer 13

the specific immune response

Question 14

what is the role of a t-lymphocyte?

Answer 14

to recognise non-self antigens presented on the surface of other body cells

Question 15

what are antigen presenting cells?

Answer 15

cells that present antigens on their surfaces

Question 16

give 3 examples of antigen presenting cells

Answer 16

• cells that are infected by virus
• a phagocyte which has just engulfed and hydrolysed a pathogen
• an abnormal cell such as a cell which has become cancerous

Question 17

explain why the secondary response is much faster than the primary one

Answer 17

there are many memory cells present specific for this antigen (after first exposure). upon activation, they can rapidly divide by mitosis to rapidly produce large numbers of plasma cells and antibodies. pathogens will be destroyed before symptoms caused.

Question 18

give two similarities and two differences between the cellular response and the humoral response to a pathogen

Answer 18

• the humoral response targets pathogens circulating in the blood where as cellular response targets pathogens in host cells
• the humoral response involves plasma cells however the cellular response involves cytotoxic cells
• both responses involve memory cells and lymphocytes
• both responses are also co ordinated by t-helper cells

Question 19

suggest 3 cell organelles that you might expect to find in large quantities in plasma cells and explain why.

Answer 19

• mitochondria produce atp (via aerobic respiration) for synthesis of antibodies
• rough er make antibodies as theses are proteins (ribosomes do protein synthesis)
• golgi apparatus processes and packages antibodies (proteins) prior to release

Question 20

what is the difference between an antigen an an antibody?

Answer 20

• antigen stimulates an immune response where as and antibody is involved in the immune response
• antigens are found in cell membranes where as antibodies are released by plasma cells

Question 21

in the elisa test, why are the washes needed after adding the second antibody?

Answer 21

to remove unbound antibodies. this prevents a false positive result

Question 22

in the elisa test what would happen if there are no antigens present in the sample?

Answer 22

the 2nd antibodies with the enzyme attached would not bind so will be washed away, no enzyme present to hydrolyse the substrate so there will be no colour change.

Question 23

how can the elisa test be used to detect the amount of antigen present in the sample?

Answer 23

if more antigen is present, then more antigen-antibody complexes form, more enzyme substrate complexes formed, more coloured product.

Question 24

give some arguments for using monoclonal antibodies

Answer 24

potential new treatment for specific, life threatening conditions that are currently incurable

Question 25

give some arguments against using monoclonal antibodies

Answer 25

• animal right issues

- drug testing issues

Question 26

define a vaccination

Answer 26

the introduction of a vaccine into an organism, with the intention of making them immune to a specific disease

Question 27

what is a vaccine?

Answer 27

an injection containing antigens and stimulates the production of antibodies and memory cells against the target pathogen without causing illness