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Cell Cycle and Immune Response (Booklet 4) > Cell Recognition and the Immune System > Flashcards

Cell Recognition and the Immune System Flashcards

1
Q

What does the immune system respond to?

A
  1. Pathogens - disease causing organisms
  2. Abnormal body cells, eg cancerous or pathogen infected cells have abnormal antigens on their surface, which trigger an immune response
  3. Toxins- these are poisons. They are molecules, not cells. Some toxins are produced by bacteria, eg Clostridium botulinum releases a protein toxin that affects the nervous system, causing botulism.
  4. Cells from other individuals eg organ transplant, blood transfusion.
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2
Q

What are the two different defence mechanisms?

A

Non- specific: Response is immediate and the same for all pathogens e.g, phagocytosis

Specific: Response is slower & specific to each pathogen e.g, T-cells, B-cells

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3
Q

What is phagocytosis?

A

phagocytes - two different types of non specific white blood cells produced in the bone marrow. They engulf and digest foreign particles throughout the body.

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4
Q

What are the two different phagocytes?

A

Neutrophils and Macrophages

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5
Q

Neutrophils?

A
  • Short lived tend to die after engulfing bacteria
  • Multilobed nucleus
  • Number rise as a result of infection
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6
Q

Macrophages?

A
  • Long lived – survive after engulfing bacteria
  • Settle in lymph nodes , spleen and kidney
  • Important in the specific immune response
  • Antigen presentation
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7
Q

What are T lymphocytes (T-cell)?

A

white blood cell that matures in the thymus and are associated with the cell mediated response, that is immunity involving body cells.

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8
Q

What are B lymphocytes (B-cell)?

A

white blood cell that matures in the bone marrow and are associated with the humoral response, that is involving antibodies that are present in body fluids or ‘humour’ such as blood plasma.

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9
Q

How do T-cells recognize the invader as foreign?

A
  1. Phagocyte has engulfed and hydrolysed the pathogen and presented the antigen.
  2. Body cells infected by virus also able to present the viral antigen.
  3. Transplanted cells from individuals of the same species have different antigens.
  4. Cancer cells are different to normal body cells and present antigens on their cell surface membrane.
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10
Q

What are helper T-cells?

A

T-cells that release chemical signals that activate and stimulate phagocytes. Activates B cells to divide and secrete antibodies

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11
Q

What are cytotoxic T-cells?

A

kills abnormal and body cells infected by pathogen by secreting a protein called perforin that make holes in the cell surface membrane. These holes mean the cell surface membrane becomes freely permeable to all substances and the cell dies as a result. This is most effective against viruses as they replicate inside body cells.

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12
Q

What response are T-cells associated with?

A

Cell-mediated response

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13
Q

What response are B-cells associated with?

A

Humoral response

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14
Q

What do plasma B-cells do?

A

secrete antibodies usually into blood, the production of antibodies and memory cells is known as the primary immune response.

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15
Q

What do memory B-cells do?

A

responsible for the secondary immune response. Memory cells live considerably longer than plasma B cells, often for decades. These cells do not produce antibodies directly, but circulate in the blood and tissue fluid. When they encounter the same antigen again they divide rapidly and differentiate into plasma B cells and more memory cells. This provides long term immunity. The secondary immune response results in increased quantity of antibodies secreted at a faster rate than the primary immune response

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16
Q

Difference between the primary and secondary immune response?

A

Primary immune response - time to produce cloned plasma B cells which secrete antibodies complementary to the pathogens antigen. The antibody level in the blood will rise, however the delay can result in the person suffering from the disease. Once the pathogen has been eliminated the blood antibody level falls. Specific Memory B cells will remain in the body.

Secondary Immune Response - If the pathogen reinvades the body, memory B cells clone rapidly to produce more antibodies at a faster rate.

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17
Q

What is the structure of an antibody?

A

Large Y shaped protein molecules that can recognise and neutralise antigens

made up of 4 polypeptide chains- 2 heavy and 2 light chains. Each has a specific binding site complementary to the antigen. They bind to the antigens on the surface of the pathogen to form antigen-antibody complexes. Each binding site consists of a sequence of amino acids that form a specific 3-D shape that binds directly to a specific antigen. The rest is the constant region this is the same for all antibodies.

Produced by B lymphocytes

18
Q

How are antibodies able to combat pathogens?

A
  1. ) Agglutination
  2. ) Neutralization
  3. ) Act as markers
19
Q

What happens during Agglutination?

A

forming antibody-antigen complexes, the pathogens are held together in large clumps. Macrophages and neutrophils can more easily engulf pathogens which are immobilised by agglutination.

20
Q

What happens during Neutralization?

A

Antigens which are toxins are rendered harmless if they are blocked by being bound to an antibody.

21
Q

What happens when antibodies act as markers?

A

They act as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached.

22
Q

What are monoclonal antibodies?

A

antibodies produced from a single group of genetically identical B-cells (plasma cells). They are identical and specific to one antigen. They can be produced in the laboratory for treating illness and medical diagnosis.

23
Q

How are monoclonal antibodies used in cancer treatement?

A

Anti-cancer drugs targeted to cancer cells.
Monoclonal antibodies can be produced that will bind to the tumour marker. You can attach anti-cancer drugs to the antibodies. This means the drug will only accumulate in the body where there are cancer cells, so the side effects are less. Eg Herceptin used to treat breast cancer.

24
Q

How are monoclonal antibodies used?

A
  1. ) Anti-cancer drugs

2. ) Medical diagnosis

25
Q

How are monoclonal antibodies used in medical diagnosis?

A

used as a tool in diagnosing disease such as influenza, hepatitis as well as certain cancers such as prostate cancer in men and pregnancy testing.

26
Q

What is the difference between direct ELISA and indirect ELISA

A

Direct ELISA - uses one antibody that is complementary to the antigen

Indirect ELISA - uses two different antibodies.

27
Q

What happens during direct ELISA?

A
  1. Collect a sample from a patient- this will contain the antigen
  2. Add antibody with enzyme attached
  3. If antigen present antibody binds
  4. Wash to remove any unbound antibodies
  5. Add substrate complementary to enzyme
  6. Coloured product formed if positive
28
Q

What happens during indirect ELISA?

A

Antigen bound to the bottom of well

Sample of patients blood plasma added. Any antibodies specific to antigen will bind.

Wash to remove any unbound antibodies

A second antibody is added that has enzyme attached. This will bind to the HIV (1st) antibody.

Wash to remove any 2nd antibodies that have not bound.

Substrate added and any colour change will indicate a positive result

29
Q

What is active immunity? What is natural and artificial active immunity?

A

Immune system produces its own antibodies after being stimulated by an antigen.

  1. Natural- results from individual becoming infected with a disease under normal circumstances. The body produces its own antibodies.
  2. Artificial – involves inducing an immune response eg vaccination
30
Q

What is passive immunity? What is natural and and artificial passive immunity?

A

Introduction of antibodies into individuals from an outside source. Immune system does not produce any antibodies of its own.

  1. Natural – antibodies from mother passed through placenta or breast milk.
  2. Artificial – injected with antibodies eg tetanus
31
Q

What are the differences between active and passive immunity?

A

Active immunty - Requires exposure to antigen,
Immune response takes a while,
Memory cells are produced,
Long term protection

Passive immunity - Does not require exposure to antigen, Immediate protection, Memory cells not produces, Short term protection as antibodies get broken down

32
Q

What is vaccination?

A

deliberate exposure to harmless antigenic material to activate the immune response, antibodies and memory B cells which provides immunity.

Vaccines protect individuals that have them and because they reduce the occurrence of the disease, those not vaccinated are also less likely to catch the disease. This is called herd vaccination/immunity.

33
Q

Why are vaccines sometimes unable to eradicate a disease?

A
  • Vaccinations fails to induce immunity in certain individuals.
  • Pathogen may mutate so its antigens change (antigenic variation). Therefore vaccine no longer effective. Eg influenza virus mutates frequently
  • There may be many varieties of a particular pathogen so it would be impossible to develop a vaccine that is effective against them all. Eg there are over 100 varieties of the common cold.
  • Individuals may have objections to vaccinations for religious, ethical or medical reasons.
34
Q

What are ethical issues for vaccines?

A
  • Vaccines are tested on animals.
  • Testing on humans can be risky.
  • Vaccines have side effects that may cause long term harm.
  • To be fully effective the whole population should be vaccinated
35
Q

What are the ethical issues for monoclonal antibodies?

A
  • Production of monoclonal antibodies involves the use of mice. Mice used to produce antibodies and tumour cells are deliberately induced to have cancerous cells.
  • Monoclonal antibodies have been used successfully to treat diseases, however there have been some deaths associated with their use in the treatment of multiple sclerosis.
36
Q

Why are antibiotics ineffective against viruses?

A

Antibiotics work by preventing the bacteria from making a normal cell wall.

Eg penicillin works by inhibiting enzymes required for the synthesis and assembly of the peptide cross linkages in bacteria cell wall (peptidoglycan) this weakens the walls making them unable to withstand pressure, so as water enters by osmosis the cell bursts and the bacteria die

37
Q

What is HIV (human immunodeficiency virus)?

A

virus that affects the human immune system. It eventually leads to acquired immune deficiency syndrome (AIDS).

38
Q

What is AIDS (acquired immune deficiency syndrome)?

A

AIDS is a condition where the immune system deteriorates and eventually fails. This makes someone with AIDS more vulnerable to other opportunistic infections like pneumonia and tuberculosis. Occurs after HIV.

39
Q

What does HIV do?

A

HIV infects and eventually kills helper T cells, which act as the host cells for the virus. Without the Helper T cells the immune system is unable to respond effectively. People infected with HIV develop AIDS when the helper T cell numbers reach a critically low level.

During the initial infection period, HIV replicates rapidly in the Helper T cell and the infected person may develop flu-like symptoms. After this period replication drops to a lower level- the latency period, during this period the virus remains dormant in the cells. During this time a person will not have any symptoms. (this can be 10 years).

40
Q

How does HIV replication occur in helper T-cells?

A
  1. ) attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell
  2. ) Capsid released, uncoats and releases RNA into the cells cytoplasm
  3. ) inside the cell, reverse transcription takes place to make a complementary strand of DNA from the viral RNA template
  4. ) From this, double stranded DNA is made and inserted into the human DNA
  5. ) Host cell enzymes used to make viral proteins from the viral DNA found within the human DNA
  6. ) Viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells

Cell Cycle and Immune Response (Booklet 4) (2 decks)

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