Vaccines, Disease + Monoclonal Antibodies

Question 1

What is a vaccine?

Answer 1

• when small amounts of weakened or dead pathogen or antigens are introduced in the mouth or by injection

Question 2

How do vaccinations help prevent diseases?

Answer 2

• weakened or dead pathogen introduced to body
• exposure to antigens activates B cell to undergo mitosis (clonal expansion) = large number which differentiates into plasma cells or memory B cells (clonal selection)
• plasma cells make antibodies
• memory B cells rapidly divide into plasma cells when reinfected = lots of antibodies

Question 3

How does herd immunity prevent the spreading of diseases?

Answer 3

• when a large proportion of pop. has been vaccinated = difficult for pathogen to spread amongst pop.
• protects those not vaccinated (e.g. children + those w weak immune system)

Question 4

How does antigen variability affect vaccines?

Answer 4

• pathogens DNA can mutate frequently: can change shape of antigen so previous immunity is no longer effective bc memory cells are no longer complementary
• e.g. influenza virus

Question 5

What are the 2 types of immunity?

Answer 5

• active immunity
• passive immunity

Question 6

What is active immunity?

Answer 6

• when exposure to a pathogen, or its antigen, triggers organisms own immune system to create antibodies

Question 7

What are the 2 types of active immunity?

Answer 7

• natural active immunity
• artificial active immunity

Question 8

What is natural active immunity?

Answer 8

• when organism is naturally infected w pathogen + so creates its own antibodies + memory cells

Question 9

What is artificial active immunity?

Answer 9

• when organism is exposed to pathogen or antigens (weakened) through a vaccination = stimulates own antibodies + memory cells to be produced

Question 10

What is passive immunity?

Answer 10

• when antibodies (from another persons immune system) are introduced into a persons body so no plasma cells or memory cells are produced: no long-term immunity

Question 11

What are the 2 types of passive immunity?

Answer 11

• natural passive immunity
• artificial passive immunity

Question 12

What is natural passive immunity?

Answer 12

• when antibodies, produced from a diff organisms immune system, are naturally introduced to an organism
• e.g. antibodies passed through breast milk to a baby

Question 13

What is artificial passive immunity?

Answer 13

• when antibodies, produced from a diff. organisms immune system, are introduced to an organism through an injection/transfusion

Question 14

What is Human Immunodeficiency Virus (HIV)?

Answer 14

• a retrovirus (virus w ability to make DNA from RNA bc contains enzyme reverse transcriptase) that targets helper T cells + are unable to survive outside human body

Question 15

How is HIV transmitted?

Answer 15

• by direct exchange of body fluids such as:
  
  • sexual intercourse
  • blood donation
  • sharing needles: used by intravenous drug users
  • from mother to child across placenta
  • mixing of blood between mother + child during birth
  • from mother to child through breast milk

Question 16

What is the structure of HIV?

Answer 16

• core: 2 RNA strands + enzyme reverse transcriptase = needed for viral replication
• capsid: protein coat
• viral envelope: lipid bilayer from host’s cell membrane
• attachment proteins: on exterior of envelope + helps attach itself to host’s helper T cell

Question 17

How does HIV replicate?

Answer 17

• HIV is transported around in blood + attaches to a CD4 receptor on a helper T cell
• HIV protein capsule fuses w helper T cell membrane = viral RNA + enzymes enter cell
• HIV enzyme, reverse transcriptase, makes a DNA copy of viral RNA: inserted into chromosomes within helper T cell nucleus
• so each time cell divides viral DNA is copied = more infected cells
• viral DNA is transcribed into viral mRNA = helper T cell use to create viral proteins to make new viral particles
• HIV particles destroy helper T cell as it leaves + infects other helper T cells

Question 18

What is AIDS (acquired immunodeficiency syndrome)?

Answer 18

• a disease, caused by HIV (virus), that causes an individual to no longer produce antibodies

Question 19

How does HIV cause the symptoms of AIDS?

Answer 19

• HIV destroys + reduces number of helper T cells
• so host is unable to produce an adequate immune response to other pathogens (can’t fight off infections)
  - vulnerable to infections + cancer
• destroys immune system: leads to death

Question 20

Why are antibiotics ineffective against viruses (v) (such as HIV)?

Answer 20

• (v) have no cell wall which antibiotics target
• (v) are non-living particles so have no metabolism or cell structure for antibodies to act on + disrupt

Question 21

What is a monoclonal antibody?

Answer 21

• single type of antibody that can be isolated + cloned

Question 22

What are monoclonal antibodies used for?

Answer 22

• medical treatment
• medical diagnosis
• pregnancy tests

Question 23

What are the 2 ways monoclonal antibodies are used for targeted medical treatment?

Answer 23

• direct monoclonal antibody therapy
• indirect monoclonal antibody therapy

Question 24

What is an example of direct monoclonal antibody therapy?

Answer 24

• used to treat certain cancers
• antibody designed w complementary binding site to antigens on cancer cells
• antibodies given to cancer patient + attach to cancer cells = prevents other chemicals, which enable uncontrolled cell division, binding to cancer cells: prevents more cancer cells being produced

Question 25

What is an example of indirect monoclonal antibody therapy?

Answer 25

• also used to treat cancer
• antibodies, which are complementary to antigens on cancer cells, have drugs attached to them
• so as antibody attaches to cancer cell, drugs are also directly delivered to cancer cell + kills it: dec harmful side effects that chemotherapy + radiotherapy can produce

Question 26

What are examples of the use of monoclonal antibodies in medical diagnosis?

Answer 26

• pregnancy tests
• diagnosing HIV
• detecting cancer cells
• detecting presence of antibodies in milk
• detecting presence of pathogens (e.g. Streptococcus bacteria)

Question 27

How are monoclonal antibodies used in medical diagnosis?

Answer 27

• can be used in test kits to diagnose diseases or conditions
  
  • quick + reliable
• e.g. via an ELISA test

Question 28

What is an ELISA test?

Answer 28

• ELISA = enzyme-linked immunosorbent assay
• used to see if a patient has any antibodies to a certain antigen (+ vice versa)

Question 29

Describe the method used in an ELISA test that tests for antibodies.

Answer 29

• antigens are bound to bottom of a well
• a test sample (e.g. blood) is added, in which complementary primary antibodies bind to antigens
• wash to remove any unbound antibodies in test sample
• add secondary antibodies, w enzyme attached, that are complementary + bind to the primary antibodies
• wash to remove any unbound enzyme-linked antibodies
• substrate is added + reacts w enzyme to form a coloured product: causes a colour change showing antibody is present

Question 30

Describe the method used in a ELISA test that tests for antigens.

Answer 30

• primary antibodies are bound to bottom of well
• a test sample (e.g. blood) is added, in which complementary antigens bind to antibodies
• wash to remove any unbound antigens in test sample
• add secondary antibodies, w enzyme attached, that are complementary + binds to primary antibodies if antigens are present
• wash to remove any unbound secondary antibodies
• a substrate is added + reacts w enzyme to form a coloured product causing a colour change showing antigen is present

Question 31

What are the ethical issues associated w the use of vaccines?

Answer 31

• debate on weather testing on animals before human-trials + using animal-based substances to produce vaccines is unethical
• debate on weather parents, who refuse to take a vaccine due to the possibility of side effects, should be allowed to refuse letting their children be vaccinated

Question 32

What are the ethical issues associated w the use of monoclonal antibodies?

Answer 32

• often revolve around animal rights issues:
  
  • debate on weather testing new monoclonal antibody therapies on animals, before human-trials, is unethical
  • debate on weather using animals to produce cells that make monoclonal antibodies, is an unethical use of animals

Question 33

What are the 3 things to consider if asked to evaluate the methods or results of an experiment in an exam?

Answer 33

• repeatability:
  - were enough repeat readings or measurements taken?
  - would you get similar results if you repeated the experiment?
• reproducibility:
  - how do the results compare w other ppl’s results?
  - would other scientists get similar results if they repeated someone else’s experiment?
• validity:
  - does the data answer the original research question?
  - were all control variables sufficiently controlled?