Cell immunity COPY

Question 1

Describe the Direct ELISA test

Answer 1

Antibodies are bound to the bottom of the well in a well plate and are immobilised

A blood sample from the patient is inserted into the well

If the blood sample contains pathogen’s antigen, the antigen will bind to the antibody, as they are complementary in shape

The well is washed out to remove any unbound antigens

Add enzyme attached to antibodies

Antibodies with enzyme bind to antigen

wash out the well to remove unbound antibodies

the enzyme-substrate complex between the antibody with enzyme and antigen results in a colour change

Question 2

Describe the Indirect ELISA test

Answer 2

Antigens are bound to the bottom of the well in a well plate and are immobilised

A blood sample from the patient is inserted into the well

If the blood sample contains antibodies, the primary antibody will bind to the antigen, as they are complementary in shape

The well is washed out to remove any unbound antibodies

Add enzyme attached to antibodies (secondary antibodies)

secondary antibodies bind to primary antibodies

wash out the well to remove unbound antibodies

solution changes colour

Question 3

Why are control centres important in monoclonal antibody tests?

Answer 3

prevents false negative results since it shows that the antibodies (from the reaction site) which would bind to pathogen has moved up the strip

Question 4

Why do we need to wash the wells thoroughly in between steps?

Answer 4

to prevent false positives

Question 5

What are the ethical worries about using mice to produce monoclonal antibodies?

Answer 5

The mice are deliberately induced with cancer to grow tumours and produce antibodies, which will cause suffering despite guidelines trying to minimise this.

Question 6

What are the ethical worries about the side effects from the use of monoclonal antibodies?

Answer 6

Rarely, death can occur in patients with multiple sclerosis, therefore it is important that patients know the risks and benefits of the drug before being taking it (informed consent).

Question 7

What are the ethical worries about trialling new drugs?

Answer 7

can present dangers to the individual involved

Question 8

After a disease is diagnosed, monoclonal antibodies are used in some medical treatments. Give one example of using monoclonal antibodies in medical treatments (3)

Answer 8

Targets pathogens

carries drug to specific cells

blocks antigens on cells

Question 9

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why?

Answer 9

specific primary structure

specific tertiary structure

only binds to one antigen

Question 10

What is the definition of immunity?

Answer 10

the ability of an organism to resist infection

Question 11

What is passive immunity?

Answer 11

person given antibodies, these work then die, no long term immunity, no memory cells.

Question 12

What is active immunity?

Answer 12

stimulation of the production of antibodies = direct contact with the pathogen or its antigen

the individual has memory cells – can make their own antibodies & provides long term immunity

takes a long time to develop

Question 13

How does activity immunity occur?

Answer 13

naturally = by primary infection

artificially = by vaccination

Question 14

How does passive immunity occur?

Answer 14

naturally = from mother to baby (placenta or breast milk)

artificially = by injection

Question 15

How do vaccines produce effective immunity to disease?

Answer 15

• Administration of the antigen or weakened pathogen to activate Immune system
• causes immune response
• engulfed by a phagocyte (macrophage), then antigens present on cell surface membrane
• T cells with complementary receptor binds to the antigen, which activates T helper cells
• T cells divide by mitosis to form clones = memory cells
• secrete cytokines activate B cells with complementary antibodies in a process known as clonal selection
• B cells divide by mitosis to form a clone (clonal expansion)
• some form memory cells- remain in body = allows a more rapid and stronger secondary response
• No symptoms of the disease when exposed to real pathogen

Question 16

What are the features of a successful vaccination programme (5)

Answer 16

• must be economically available in sufficient quantities to immunise most of the vulnerable population
• must be few side affects or this may discourage individuals in the population from being vaccinated
• means of producing, storing and transporting the vaccine must be available
• must be able to administer the vaccine properly with trained staff
• must be possible to to vaccinate the vast majority of the vulnerable population to produce herd immunity

Question 17

What is herd immunity?

Answer 17

when a large proportion of the population is vaccinated,

therefore most people will be immune, only a few will not be a immune,

increases chance of non-immune person coming into contact with immune person,

so the pathogen has no where to go, and is unable to replicate = destroyed

Question 18

What are the problems with vaccination programmes? (6)

Answer 18

• the vaccine does not work (dead form ineffective, pathogen hides from the immune system by concealing themselves inside cells , or by living in places out of reach)
• vaccine not safe (no weak/inactive form, causes major side effects)
• cannot achieve herd immunity (logistic of vaccinating large proportion)
• antigenic variability = immunity shortlived
• many strains of the pathogen
• individuals may develop the disease immediately after vaccination but before their immunity levels are high enough to prevent it . These individuals may harbour the pathogen and reinfect others

Question 19

Why are more than one injections of vaccines normally given? (3 )

Answer 19

more antigens = more memory cells = more antibodies/ antibodies produced quicker

Question 20

What are vaccines?

Answer 20

a serum that contains dead or weakened pathogens, which stimulate the production of antibodies

Question 21

What are the factors that should be considered before the drug can be used o patients with disease?

Answer 21

• dosage of drug
• cost of drugs
• how effective it is
• no serious side effects

Question 22

Draw and label the structure of HIV. Explain each feature (what is the lipid envelope made from, what does the capsid have inside, what does reverse transcriptase and attachment do, what is the genetic material?) (6)

Answer 22

Attachment protein: allows HIV to attach to cells surface of T helper Cells

Reverse transcriptase: catalyzes the production of DNA from RNA and is needed for virus replication

Capsid: encloses two single strands of RNA and some enzymes

Genetic material: two single strands of RNA

lipid envelope: made from the membrane stolen from the cell membrane of the precious host cell

Question 23

What does HIV stand for?

Answer 23

human immunodeficiency virus

Question 24

Describe and explain the replication of HIV

Answer 24

• HIV circulates in the bloodstream and the attachment protein on the HIV binds to the CD4 receptors on the helper T cells
• Lipid envelope Protein fuses with the cell-surface membrane and the RNA and enzymes of HIV enter the helper T cell
• HIV reverse transcriptase converts the virus’s RNA into DNA
• This DNA moves into the T helper cell’s nucleus, it releases an integrase enzyme that inserts the viral DNA into the human DNA. The virus becomes incorporated into the hosts genetic material
• This DNA now codes for new viral proteins
• These are assembled to make a HIV virus
• HIV viruses break away from the helper T cell with a piece of its cell-surface membrane surrounding them which forms their lipid envelope

Question 25

Why does it take many years for AIDS to develop?

Answer 25

Because HIV often goes into dormancy

Question 26

How does HIV cause the symptoms of AIDS?

Answer 26

without helper T cells a person cannot stimulate antibodies or cytotoxic T cells = person is unable to produce an adequate immune response so they become susceptible to other infections and cancers

Question 27

Why don’t antibiotics work on viruses?

Answer 27

Cells walls: antibiotics interfere with bacterial cell wall by preventing the production of muerin, so that when the water enters the bacteria, the weak walls are unable to withstand the pressure= cause the cell to burst

Viruses do not have cell walls, they have protein coats from host cell, so there are no sites where antibiotics can work

Metabolic pathways: antibiotics disrupt metabolic pathways and viruses don’t have their own metabolic pathway to disrupt as they use host cell’s metabolic pathways.

Also, due to replicating in the host cell, they are difficult to access = antibiotics cannot reach them.

Question 28

How does HIV avoid being recognised and destroyed by lymphocytes?

Answer 28

by repeatedly changing its protein coat