5. Cell recognition and the immune system

Question 1

What are monoclonal antibodies?

Answer 1

Antibodies produced from a single group of genetically identical b-cells (plasma cells) specific to one type of antigen.

Question 2

Why are all monoclonal antibodies identical in structure?

Answer 2

They have the same primary structure as they are all coded for by the same gene.
As a result they also have the same secondary and tertiary structure.

Question 3

How are monoclonal antibodies produced?

Answer 3

The specific antigen binds to the receptor of the b-cells.
A helper t-cell sends out a chemical signal to activate the b-cell.
This releases specific antibodies.
Some plasma cells, mean identical antibodies will be produced

Question 4

Why can monoclonal antibodies be used in the creation of ‘targeting drugs’?

Answer 4

They all have the same unique tertiary structure.
This means that they will then bind to a specific antigen with a complementary shape.
Therefore, you can make monoclonal antibodies bind to a specific target molecule, such as a cell antigen.

Question 5

How can monoclonal antibodies be used in the treatment of cancer?

Answer 5

Individual types of body cells have a different type of surface antigen that can be identified.
Cancer cells carry a unique antigen called a tumour marker.
Monoclonal antibodies can be produced to bind to these tumour markers. Anti-cancer drugs can then be attached to these antibodies.
Thus the drugs will only be released where antibody binding occurs, only affecting cancer cells.
This reduces side effects because the drugs will only accumulate at specific cell sites.

Question 6

How can monoclonal antibodies be used in pregnancy testing?

Answer 6

The placenta in a pregnant woman produces the hormone HCG, this can be found in the mother’s urine.
Monoclonal antibodies are immobilised in coloured beads on a test strip.
When urine is applied, any HCG will bind to the antibodies to form antigen-antibody complexes.
The HCG-antibody-colour complex moves along the strip until it is trapped by a different type of antibody.
The creation of this specific complex accumulates to produce a coloured line confirming pregnancy.

Question 7

What are the ethical issues surrounding the production and use of monoclonal antibodies?

Answer 7

Production requires the use of mice to produce the antibodies, in order to produce them the mice must have tumour cells present in the body.
The mice must be injected with cancer cells.

Question 8

Pros and cons of the use of monoclonal antibodies in humans?

Answer 8

Pro: Positive results in treating cancer and diabetes.
Con: Negative results involve deaths in treating multiple sclerosis. - In 2006 a drug trial involved the injecting of monoclonal antibodies into patients suffering with multiple sclerosis. Within minutes 6 participants went into multiple organ failure.

Question 9

on a basic level, how does a virus replicate?

Answer 9

Virus attaches to host cell and injects its genetic material
The genetic material is used as a code to synthesise proteins in the nucleus
New virus particles are assembled
Viruses burst out of and destroy the host cell

Question 10

what two regular functions of cells can viruses not perform?

Answer 10

respire

photosynthesise

Question 11

explain the function of a attachment protein when looking at viruses

Answer 11

allows the virus to attach to the host cell

Question 12

explain the purpose of DNA/RNA when looking at viruses

Answer 12

proteins that encode for the virus

Question 13

explain the purpose of a capsid when looking at viruses

Answer 13

protein coat that encapsulates the DNA/RNA

Question 14

explain the purpose of nucleoproteins when looking at viruses

Answer 14

accessory protein e.g enzymes

Question 15

true/false
viruses are not formed of cells
viruses are considered non-living

Answer 15

true

true

Question 16

what is HIV?

Answer 16

Human Immunodeficiency Virus

interferes with the functioning of the immune system.

Question 17

why is HIV called a retrovirus?

Answer 17

because it uses the enzyme reverse transcriptase to perform reverse transcription

Question 18

what is AIDS?

Answer 18

a disease of the immune system, HIV kills or interferes with normal functioning of the immune system, leading to AIDS
However not always a result of HIV

Question 19

how can you test for HIV?

Answer 19

ELISA testing.

enzyme linked immunosorbent assay

Question 20

how does an ELISA test work?

Answer 20

It uses antibodies to detect the presence of certain proteins (antigens) , CD4

Question 21

why do antibodies not work against viral diseases?

Answer 21

viruses have no metabolic processes or cell structures for antibiotics to disrupt.
a virus protein coat means that antibiotics can not bind to sites.

Question 22

How does HIV replicate?

Answer 22

through the use of helper T-cells

the attachment proteins on the virus are complementary to the proteins on the surface of T-helper cells

Question 23

Explain some advantages of ELISA testing

Answer 23

very sensitive so can detect the smallest amounts of protein.
can also be used to detect hepatitis and tuberculosis, not just HIV
can also be used to detect the amount of drugs in a person’s system

Question 24

Explain why AIDS is deadly to sufferers?

Answer 24

AIDS sufferers have around 200mm-3 T-helper cells circulating opposed to the healthy 1000mm-3
sufferers develop small infections a lot easier and faster. complications of infections are also far more likely to be deadly
Usually HIV/AIDS does not kill a person, the ill health associated with it does

Question 25

describe the life cycle of HIV

Answer 25

binding
fusion
reverse transcription (RNA --> DNA)
integration
replication
assembly
budding

Question 26

what happens when HIV buds off the cell

Answer 26

it takes a piece of the cell membrane with it

these cell membrane proteins can prevent the body from recognising the virus as foreign

Question 27

what happens when integration occurs during the life cycle of HIV?

Answer 27

the cell produces messenger RNA to create new viral cells

Question 28

what is an antigen?

Answer 28

any part of an organism (often a protein on the surface of a cell) that is recognised as foreign by our immune system.

Question 29

what can our immune system identify by their antigens?

Answer 29

pathogens
cells from other organisms of the same species
cancerous cells
toxins

Question 30

why are transplant organs taken from relatives?

Answer 30

antigens are genetically controlled - close relatives have more similar antigens

Question 31

what are the two types of immune systems? (defence mechanisms) and what types of organisms have which?

Answer 31

non-specific - all animals

specific - only vertebrates

Question 32

what are the features of a non-specific immune system response?

Answer 32

phagocytosis by phagocytes
phagocytes ‘swallow’ foreign body’s
physical barriers, e.g. skin and stomach acid

Question 33

what are the features of a specific immune system response?

Answer 33

B and T lymphocytes 
T lymphocytes (cell mediated response)
B lymphocytes (humoral response)

Question 34

list and describe some physical barriers to infection?

Answer 34

the skin - physical barrier that pathogens find difficult to penetrate
hydrochloric acid - found in the stomach, denatures the enzymes or protein coats of most pathogens that enter the stomach
epithelial mucus - epithelial layers inside the body produce mucus that pathogens stick to and become immobilised

Question 35

describe the process of phagocytosis

Answer 35

the phagocyte is attracted to the pathogen and binds to it
the pathogen is engulfed by the phagocyte to form a vesicle, known as a phagosome
lysosomes within the phagocyte migrate towards the phagosome
digestive enzymes are released into the phagosome, where they digest the pathogen
antigens from the pathogens are produced on the surface of the phagocyte as soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte