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Immunity Flashcards

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1
Q

What are pathogens?

A

Disease causing microorganisms.

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2
Q

What type of cells are bacteria? How do they reproduce?

A

Prokaryotic cells
Reproduce rapidly by binary fission or can exchange genetic material by conjunction meaning advantageous genetic mutation can spread very quickly.

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3
Q

How does bacteria cause disease?

A

Produce pathogens that damage the body.

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4
Q

How do viruses reproduce?

A

Can’t survive or reproduce outside a host cell.
1) Enter a cell and hijack their reproductive machinery.
2)New viruses exit the cell as it bursts.
3) Most kill cells by inhibiting them or causing them to burst.

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5
Q

What type of cells are fungi?

A

Single or multicellular eukaryotic cells.

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6
Q

How do fungi obtain food and reproduce?

A

By secreting enzymes to dissolve substrates and then absorbing nutrients.
Reproduce by producing spores.

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7
Q

What does the pathogenicity of fungi depend on?

A

Level of penetration.

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8
Q

What are: superficial infections, sub-cutaneous infections and systematic infections ?

A

On skins surface, usually treatable.
Under skin, treat with anti-microbials.
In deep tissues or organs, usually fatal.

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9
Q

How does the body recognise its own cells?

A

Recognises foreign cells by specific molecules (usually proteins: glycoproteins) found in the surface of cells + viral particles. Allow the body to recognise self and non self cells.

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10
Q

What are surface proteins (glycoproteins) found on and what do they allow the body to recognise?

A
  • Pathogenic cells
  • Abnormal body cells (cancer or pathogen infected cells)
  • Toxins
  • Cells from other individuals of the same species
  • Macrophage APCs
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11
Q

What needs to happen for organ transplants to be successful?

A

The body mustn’t recognise cells/tissues of donated organ as foreign so no immune response occurs.

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12
Q

How do lymphocytes learn to recognise self antigens in foetus’s?

A

1) In the fetus the millions of lymphocytes present are constantly colliding.
2) Infection in rare as it’s shielded from the outside world.
3) Lymphocytes will collide exclusively with self antigens.
4) If the lymphocyte has receptors that exactly fit self antigens they will die/ are suppressed.
5) The only remaining lymphocytes are those that might fit foreign material and therefore respond to foreign material.

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13
Q

How do lymphocytes learn to recognise its own cells in adults?

A

1) Lymphocytes produced in the bone marrow will only initially encounter self antigens.
2) Any lymphocytes that initiate an immune response to self antigens undergo apoptosis before differentiating into mature lymphocytes.
3) No anti-self lymphocytes will therefore appear in the blood.
4) This leaves only lymphocytes which respond to anti self antigens.

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14
Q

What is apoptosis?

A

Programmed cell death

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15
Q

What are the two types of defence mechanisms?

A

Non specific
Specific

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16
Q

What is a non specific response? Give two examples.

A

Response is immediate and the same for all pathogens.
Physical barrier and phagocytosis

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17
Q

What is a specific response? Give some examples.

A

Response is slower and specific to each pathogen.
Cell mediated and humoral responses

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18
Q

What are the two types of white blood cells?

A

Phagocytes and lymphocytes

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19
Q

What are the two types of phagocytes?

A

Neutrophils and macrophages

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20
Q

What is phagocytosis?

A

Phagocytes ingesting and destroying pathogens before they can cause harm. They also remove dead cells.

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21
Q

What are the steps involved in phagocytosis?

A

1) Chemical products of pathogens act as attractions.
2) Phagocytes move towards the pathogen.
3) The phagocyte has receptor on membrane that recognise and attach to the pathogen’s antigen.
4) Pathogen is engulfed, forming a phagosome.
5) Lysosomes fuse with the phagosome.
6) Lysozyme enzyme destroy ingested bacteria by hydrolysis of their cell wall.
7) The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte.

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22
Q

What are macrophages?

A

WBC that are capable of moving into organs rather than remaining in the blood. Carry out phagocytosis but don’t completely destroy the pathogen.

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23
Q

What steps are there for macrophages in phagocytosis?

A

1) They cut up the pathogens so they can display the antigens of the pathogen on their surface.
2) This now becomes an antigen presenting cell that can be recognised by lymphocytes.

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24
Q

What are lymphocytes?

A

Type of WBC produced in the bone marrow. They are smaller than phagocytes with a large nucleus.

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25
What are the two types of lymphocytes?
B-lymphocytes (B cells) T-lymphocytes (T cells)
26
Where do T-lymphocytes mature?
Thymus gland
27
What are the 4 types of T cells?
1) T helper cells 2) T effector cells 3) Cytotoxic T cells 4) T memory cells
28
What does a T helper cell do?
Binds to the antigen when pathogen enters the body. Contains CD4 receptors. Activate B cells.
29
What does a T effector cell do? When are they produced?
Same as T helper cells. Produced once T helper cells have divided.
30
What does a cytotoxic T cell do?
Kill cells infected with a virus. Can recognise non self cells.
31
What does a T memory cell do? When are they produced?
Create a faster immune response on reinfection. Produced when T helper cells remain in the body.
32
What is an antigen presenting cell?
A phagocyte that has engulfed then hydrolysed a pathogen then displays the pathogen's antigens on its surface.
33
What are the steps in the cell-mediated response?
1) Pathogens invade the body cells and phagocytes digest them to form APC. 2) Specific receptors on the T helper cells respond to APC by binding to antigen. 3) Activates T helper cell which divides rapidly via mitosis forming clones. 4) Clones can a) differenciate into memory cells b) stimulate phagocytes c) stimulate B cells to divide + produce antibodies d) activate cytotoxic T cells.
34
How do cytotoxic T cells kill an abnormal/infected cell?
Produce the protein perforin. Perforin makes holes in the cell surface membrane making it freely permeable to all substances so the cell dies.
34
In which case are T killer cells most effective?
When killing viruses. A virus exists in cells so by killing the cell the virus can't replicate.
35
What do T helper cells secrete?
Cytokines
36
What are cytokines?
Group of hormones that include growth factors that initiate cell division, cell toxins to speed up cell destruction and interferons to protect cells from further infection. Stimulate B cells to divide.
37
True or false: B-lymphocytes remain in the bone marrow.
True
38
True or false: Each B cell can make more than one type of antibody.
False
39
Describe the steps in the primary humoral response.
1) Clonal selection: Pathogen enters the body with unique antigen. 2) B cell with complimentary antibody attaches. 3) Antigen enters B cell via endocytosis. 4) Antigen is processed + presented on B cell's surface. 5) Clonal expansion: T helper cells with complimentary receptor binds to the processed antigens and stimulate the B cell to divide by mitosis. 6) daughter cells become either memory cells or plasma cells that secrete antibodies that destroy the pathogen.
40
Describe what happens in the secondary humoral response.
If the antigen is encountered again the memory cells will divide rapidly and differentiate into plasma cells which produce antibodies to destroy the pathogen. New memory cells are made to provide long term immunity.
41
Why are memory cells needed for a secondary response?
The plasma cells only survive for a couple of days.
42
True of false: Antibodies are made at a slower rate and at lower concentrations during the secondary response.
False
43
What is the structure of an antibody?
Quaternary structure with 4 polypeptide chains: 2 heavy, 2 light. Has an specific antigen binding site called variable region ( has a specific sequence of amino acids which forms a specific 3D shape which binds to the specific antigen). Hinge region provides flexibility. Disulphide bridge.
44
What is agglutination?
Antibodies can bind to 2 pathogens at once causing groups of pathogens to clump together.
45
Why is agglutination beneficial?
Makes pathogens less spread out and therefore the pathogen can be easily located to be killed. Act as markers that stimulate phagocytosis.
46
What are monoclonal antibodies?
Artificially produced antibodies that bind to and inactivate a specific antigen.
47
How are monoclonal antibodies made?
By injecting mice with an antigen. The mice produce the lymphocyte that makes the antibody. Antibody is then fused with myeloma (cancer) cells that divide forever.
48
What the properties of monoclonal antibodies?
- Identical clones of each other - Produced in large quantities at low costs - Highly specific
49
What are the ethical issues surrounding monoclonal antibodies?
- Using mice and specifically inducing cancer cells. - Deaths when treating multiple sclerosis - Drug trials in healthy volunteers induced organ failure within minutes.
50
How is Elisa testing used to detect HIV, describe the steps?
1) HIV antigen bound to bottom of reaction vessel. 2) Blood plasma sample added HIV antibodies will bind to the antigens. 3) Wash away non specific antibodies. 4) Secondary antibody attached with enzyme. 5) Substrate added and enzyme if present reacts causing a colour change.
51
What diseases are tested for using antibodies?
STDs or parasitic
52
What is a benefit of using antibodies for diagnosis?
Less side effects as they specifically target cells.
53
How can monoclonal antibodies kill cancer cells?
Attach to receptors on the cancer cells and the attach to cell surface blocking signals that stimulate uncontrolled growth. Can attach cytotoxic drugs to antibodies to kill the cell.
54
What hormone is detected by ELISA testing when a women uses a pregnancy test?
HcG
55
What are vaccines made of?
Dead (attenuated) or weakened microorganisms
56
What makes a vaccination programme successful?
- economical to produce in large quantities - few side effects - easy to store and transport - safe and efficient administration - must be possible to give herd immunity
57
How does the body respond to a vaccine?
A vaccine contains antigens from a pathogen so: 1) Phagocytosis 2) Cell mediated response 3) Humoral response
58
What is passive immunity?
Antibodies are produced by an outside source so no memory cells are formed meaning there is no lasting immunity.
59
What is the example for natural passive immunity?
Antibodies received from another organism e.g via placenta or breast milk
60
What is the example for artificial passive immunity?
Antibodies are manufactured then injected giving immediate protection.
61
What is active immunity?
Produced by an immune response that's initiated by an antigen entering the body producing memory cells and providing long term immunity.
62
What is the example for natural active immunity?
Body is naturally exposed to a pathogen.
63
What is the example for artificial active immunity?
Vaccination
64
Give some examples as to why vaccines may not eliminate disease.
- fails to induce immunity in those with defective immune systems. - pathogen may mutate - antigenic variability - individuals may have objections to vaccines - religion, ethics - variety of particular pathogen
65
What are the ethical issues surrounding vaccinations?
- harms animals - side effects may cause long term harm - can't make it compulsory - expensive to make when almost eradicated
66
What is herd immunity?
When a sufficiently large proportion of the population has been vaccinated which makes it difficult for a pathogen to spread within the population. Those not immune are then protected as disease levels are low.
67
What are the organelles present in HIV?
- 2 RNA strands - reverse transcriptase enzyme - capsid (protein coat) - attachment proteins - viral envelope (contains lipid bilayer and glycoproteins)
68
How is HIV replicated?
1) infects T helper cell by targeting CD4 receptor 2) Protein capsid fuses with cell surface membrane and RNA and enzyme from HIV enter T cell. 3) viral RNA is converted to DNA using reverse transcriptase. 4) DNA moves into nucleus of T helper cell and inserted in the cell's DNA. 5) This DNA now creates mRNA using the cells enzymes which will code for new viral proteins. 6) mRNA passes out of the nucleus and protein synthesis occurs making new HIV particles. 7) new HIV particles break away from T helper cell with part of the cell surface membrane which becomes its lipid envelope.
69
How does the replication of HIV lead to AIDs?
HIV targets and reduces the number of T cells meaning no B cells are stimulated to produce antibodies or create T killer cells. Without a immune response the body become susceptible to infection such as AIDs.
70
True or false: HIV kills you.
False ## Footnote It is the development of AIDs (caused by the HIV weakening the immune system) that kills you.
71
Why are antibiotics not effective at killing viruses?
Viruses are non living meaning they carry out their metabolic activities in a host cell. This cell can't be targeted as it's a self cell.

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