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bio topic 2 > cell recognition and the immune system > Flashcards

cell recognition and the immune system Flashcards

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Biology 101 flashcards
1
Q

Define an Antigen [4]

A
  • When recognised as foreign by the immune system
  • Can stimulate an immune response
  • Leading to the production of antibodies
  • Usually proteins on the surface of cells
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2
Q

What do Antigens allow the immune system to identify? [4]

A
  • Pathogens
    (e.g. bacteria, viruses, fungi)
  • Cells from other organisms of the same species
    (e.g. organ transplant, blood transfusion)
  • Abnormal body cells
    (e.g. cancerous cells / tumours)
  • Toxins released from bacteria
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3
Q

Describe the Phagocytosis of Pathogens [6]

A
  • Phagocyte recognises foreign antigens on the pathogen surface and binds to the antigen
  • Phagocyte engulfs pathogen by surrounding it with its cell surface membrane and cytoplasm
  • Pathogen contained in phagosome in cytoplasm of phagocyte
  • Lysosome fuses with phagosome and releases lysozymes (hydrolytic enzymes) into the phagosome
  • These hydrolyse / digest the pathogen
  • Phagocyte becomes antigen presenting and stimulates specific immune response
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4
Q

The Cellular Response [6]

A
  • T lymphocytes recognise antigen presenting cells after phagocytosis of foreign antigen
  • The Specific T lymphocyte (T helper cell) with receptor complementary to specific antigen binds to the antigen presenting cell
  • Becoming activated and dividing rapidly by mitosis to form clones which then
  • Stimulate B cells for the humoral response
  • Stimulate phagocytes to engulf pathogens by phagocytosis
  • Stimulate cytotoxic T cells to kill infected cells by producing perforin
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5
Q

The Humoral Response [5]

A
  • Specific complementary B cell binds to antigen presenting cell
  • And is stimulated by helper T cells to
  • Divide rapidly by mitosis to form clones (clonal expansion)
  • Some become B plasma cells for the primary immune response - secrete large amounts of monoclonal antibody into blood
  • Some become B memory cells for the secondary immune response
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6
Q

Primary Response [4]

A
  • Produces antibodies slower and at a lower concentration
  • Not many B cells available that can make the required antibody
  • T helpers need to activate B cells to make the antibodies which takes time
  • So infected individual will express symptoms
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7
Q

Secondary Response [3]

A
  • Produces antibodies faster and at a higher concentration because
  • B and T memory cells present
  • B memory cells undergo mitosis quicker
  • Infected individual doesn’t express symptoms
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8
Q

Define an Antibody [3]

A
  • Quaternary structured protein
  • Secreted by B lymphocytes
  • Binds specifically to antigens forming an antigen-antibody complex
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9
Q

How do antibodies work to destroy pathogens? [3]

A
  • Binds to two pathogens at a time forming an antigen-antibody complex
  • Enables antibodies to clump the pathogens together via agglutination
  • Phagocytes bind to the antibodies and engulf many pathogens at once
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10
Q

Vaccination [3]

A
  • Injection of antigens
  • From attenuated (dead or weakened) pathogens
  • Stimulating the formation of memory cells
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11
Q

How does the use of vaccines provide protection for individuals against disease? [3]

A
  • Stimmulates the formation of memory cells
  • On reinfection/secondary exposure to the same antigen, the secondary response produces antibodies faster and at a higher concentration
  • Leading to the destruction of a pathogen before it can cause harm / symptoms
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12
Q

How does the use of vaccines provide protection for populations against disease? [2]

A

Makes it more difficult for the pathogen to spread through the population because…
- More people are immune so fewer people in the population carry the pathogen / are infected
- Fewer susceptible so less likely that a susceptible (non-vaccinated) individual will come into contact with an infected person and pass on the disease

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13
Q

What is Herd Immunity?

A

Large proportion but not 100% of population vaccinated against a disease

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14
Q

What is Active Immunity? [3]

A
  • Initial exposure to antigen
    (e.g. vaccine or primary infection)
  • Memory cells involved
  • Antibody is produced and secreted by B plasma cells
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15
Q

Give one advantage and disadvantage of Active Immunity

A

ADVANTAGE
Provides long term immunity
(antibody can be produced again in response to a specific antigen)

DISADVANTAGE
Slow, takes time to develop

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16
Q

What is Passive Immunity? [3]

A
  • No exposure to antigen
  • No memory cells involved
  • Antibody introduced into body from another
    organism
    (e.g. breast milk / across placenta from mother)
17
Q

Give one advantage and disadvantage of Passive Immunity

A

ADVANTAGE
Fast acting

DISADVANTAGE
Short term immunity
(antibody broken down / can’t be produced again)

18
Q

Give 4 ethical issues associated with the use of vaccines

A

Tested on animals before use on humans →
animals have a central nervous system so feel pain
(some animal based substances are also used to produce vaccines)

Tested on humans →
volunteers may put themselves at unnecessary risk of contracting the disease because they think they’re fully protected

Expensive →
less money spent on research and treatments of other diseases

Can have side effects

19
Q

What is Antigen Variability an explanation for? [3]

A
  • New vaccines against a disease need to be developed more frequently
    (e.g. influenza)
  • Vaccines against a disease may be hard to develop or can’t be developed in the first place
    (e.g. HIV)
  • May experience a disease more than once
    (e.g. common cold)
20
Q

Explain the effect of antigen variability on disease [6]

A
  • Change in antigen shape (due to a genetic mutation)
  • Antigen not recognised by B memory cell
  • No plasma cells / antibodies produced
  • Not immune
  • Must re-undergo primary immune response
  • Disease symptoms felt
21
Q

Explain the effect of antigen variability on disease prevention (vaccines) [3]

A
  • Change in antigen shape (due to a genetic mutation)
  • Existing antibodies with a specific shape unable to bind to changed antigens / form antigen-antibody complex
  • Immune system won’t recognise different antigens
22
Q

Monoclonal Antibody [2]

A
  • Antibody produced from a single group of genetically identical B plasma cells
  • Which bind to specific complimentary antigen
23
Q

Monoclonal Antibodies and therapeutic drugs (e.g. cancer) [5]

A
  • Monoclonal antibodies made to be complementary to antigens specific to cancer cells
  • Anti-cancer drug attached to antibody
  • Antibody binds to cancer cells, forming antigen-antibody complex
  • Delivering attached anti-cancer drug directly to specific cancer cells
  • Fewer side effects as fewer normal body cells killed
24
Q

Monoclonal Antibodies and medical diagnosis (e.g. pregnancy test) [9]

A
  • Pregnant women have the hormone hCG in their urine
  • Urine test strip has 3 parts with 3 different antibodies
  • Application area, position 1: antibodies complementary to hCG (bound to a blue coloured bead)
  • Middle, position 2: antibodies complementary to hCG-antibody complex
  • End, position 3: antibodies complementary to non-hCG hormone
    If pregnant…
  • hCG binds to antibodies in application area forming hCG-antibody complex
  • Travels up test strip, binds to antibodies at position 2 forming a blue line
    If not pregnant…
  • No hCG in urine so hCG doesn’t bind to antibodies in application area so doesn’t bind to antibodies at position 2 meaning no blue line
    Control > non-hCG hormones bind to complementary antibodies at third position, forming a blue line
25
Q

The use of antibodies in the ELISA (enzyme linked immunosorbent assay) test [3]

A

Can determine if a patient has…
- Antibodies to a certain antigen
- Antigen to a certain antibody
- Used to diagnose diseases or allergies

26
Q

How does the ELISA test work? [8]

A
  • Antigen bound to the bottom of the well
  • Patients blood sample added
  • If specific complementary antibodies are present, they will bind to the antigen
  • Wash out the well to remove unbound antibodies
  • Add a secondary antibody, complimentary to the bound antigen-antibody complex, with a specific enzyme attached to it
  • Wash well out to remove unbound secondary antibody
  • Solution containing a substrate which can react with the enzyme attached to the secondary antibody is added
  • If the solution changes colour the result is positive
27
Q

Give 2 ethical issues associated with the use of monoclonal antibody

A
  • Animals are involved in the production of monoclonal antibodies
    (e.g. by producing cancer in mice who have a central nervous system so feel pain, and it is unfair to give them a disease)
  • Although it is effective treatment for cancer and diabetes monoclonal antibodies have caused deaths when used in treatment of Multiple Sclerosis
28
Q

Give 5 components of a HIV virus

A
  • Envelope
  • Attachment Protein
  • Capsid
  • Reverse Transcriptase
  • RNA
29
Q

How is HIV replicated? [11]

A
  • HIV infects T helper cells (host cell)
  • HIV attachment protein attaches to complementary receptor on the helper T-cell membrane
  • Virus lipid envelope fuses with cell surface membrane and capsid released into cell
  • Capsid uncoats, releasing RNA and reverse transcriptase into cytoplasm
  • Viral DNA is made from viral RNA by reverse transcriptase
  • Viral DNA integrated into host cell’s DNA
  • This remains latent for a long time in host cell until activated
  • Host cell enzymes used to make viral proteins from viral DNA, which assemble to make a new virus
  • New virus bud from cell, taking some of cell surface membrane as envelope
  • Eventually kills helper T cells
  • Most host cells are infected and process repeats
30
Q

How does HIV cause the symptoms of AIDS? [4]

A
  • Infects and kills helper T cells (host cell) as it multiplies rapidly
  • T helper cells then can’t stimulate cytotoxic T cells, B cells and phagocytes
  • Immune response impaired and deteriorates
  • More susceptible to infections and diseases that wouldn’t cause serious problems in a healthy immune system are deadly
31
Q

Why antibiotics are ineffective against viruses? [3]

A
  • Antibiotics can’t enter human calls but viruses exist within its host cell as they are acellular
  • Viruses don’t have own metabolic reactions which antibiotics target
  • If we did use them it would act as a selection pressure = resistant strain of bacteria via natural selection = reducing effectiveness of antibiotics and waste money

bio topic 2 (5 decks)

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