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Y12 Immunity Flashcards

1
Q

Pathogen

A

A microorganism that causes disease

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2
Q

Defence mechanisms (2 types)

A

-Specific
-Non-specific

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3
Q

Non-specific defence mechanism

A

-Response is immediate and the same for all pathogens

-Physical Barrier: e.g Skin, preventing pathogens. Entering the body
-Phagocytosis: Engulfing and destroying pathogens

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4
Q

Specific Defence mechanism

A

-Response is slower and specific for each pathogen

-Cell mediated response: T-lymphocytes, can hunt down and destroy infected/mutated cells
-Humoral response: B-lymphocytes, secrete antibodies

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5
Q

Humoral

A

Refers to bodily fluids - blood and lymph

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6
Q

Antigen

A

A molecule that stimulates an immune response

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7
Q

What are antigens found on

A

-Pathogens (e.g. virus)
-Abnormal body cells (e.g. cancer cells)
-Toxins
-Cells form other individuals of the same species (e.g. transplants)

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8
Q

Cell-surface antigens

A

Identify cells as ‘self’
Identifies foreign material that have antigens which are different as ‘non-self’

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9
Q

How many stages are there of phagocytosis?

A

6 Stages

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10
Q

Phagocytosis stages

A
  1. Phagocyte is attracted to the pathogen by the chemicals it produces. It moves towards the pathogen up a conc. gradient (low to high)
  2. Phagocyte has receptors on cell surface membrane that attach to chemicals on the surface of the pathogen
  3. Pathogen is engulfed, forming a phagosome. Lysosomes within the phagocyte migrate towards the phagosome
  4. Lysosomes release lysozymes into phagosome, where they hydrolyse the pathogen
  5. Soluble products from the breakdown of pathogen are absorbed into cytoplasm of phagocyte
  6. Products which aren’t soluble and can’t be used by cell is released via exocytosis
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11
Q

2 types of Lymphocytes (WBC)

A

-B lymphocytes (B cells) mature in bone marrow and lead to production of antibodies
-T lymphocytes (T cells) mature in thymus gland and are involved in cell-mediated immunity. Destroy infected cells and activate other cells

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12
Q

T lymphocytes divide into 3 types of cell

A
  1. T helper cells (Th)
  2. T cytotoxic cells (Tc)
  3. T memory cells (Tm)
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13
Q

T helper cells (Th)

A

Release cytokines
- stimulate B cells to develop
- stimulate phagocytosis (cell signalling)
- develop into memory cells
- activate cytotoxic T cells

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14
Q

T cytotoxic cells (Tc)

A

Attack and kill infected body cells
- kill abnormal cells with markers for cancer
- kill non self cells (organ rejection)
- cell marked through cell signalling (proteins released by cell)
- release perforins and cytotoxins
- kills cells - antigen specific only

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15
Q

T memory cells (Tm)

A

-able to differentiate rapidly into Th and Tc cells on stimulation with Antigen

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16
Q

Cell mediated immunity

A

Binding of the T cell receptor to the antigen activated the T cell.

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17
Q

How do Th cells clone

A

Th cells have a specific receptor for the antigen. Activation causes the Th to clone by mitosis.
If clones are not used immediately, the clones can become memory cells (Tm).

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18
Q

Cell-mediated immunity stages

A
  1. Pathogens invade body cells or are taken in by phagocytes
  2. Phagocyte places antigens from the pathogen on its cell surface membrane
  3. Receptors on a specific T helper cell fit exactly onto the antigens
  4. Attachment activates T helper cells to rapidly divide through mitosis and form clones genetically identical to itself
  5. Cytotoxic T cells are activated by interaction with an antigen presenting cell and cytokines from T helper cells. Once activated, they also divide by mitosis to produce Tc Clones.
  6. Cytotoxic T cells produce perforin (protein). This makes holes in the cell surface membrane of the infected host cell and results in cell death
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19
Q

Humoral Immunity

A

B-cells are covered with antibodies. When an antigen enters the blood or tissue fluid, there will be one B-cell with a complementary antibody

20
Q

Humoral Immunity stages

A
  1. Specific T helper cell attaches to an antigen bound to an antibody on the surface of the B cell, activating the B cell and causing it to divide
  2. B cell divides through mitosis to give a clone of plasma cells (clonal selection)
  3. Plasma becomes full of ribosomes, ER and mitochondria - allows cells to produce large quantities of
  4. Cloned plasma cells produce and secrete the specific antibody that binds to the antigen on the pathogens surface and destroys it
  5. Some B cells develop into memory cells
21
Q

Memory Cells

A

-circulate the blood and tissue fluid and can respond to future infections by the same pathogen

22
Q

Secondary immune response

A

-Memory cells divide rapidly and develop into plasma cells that produce large amounts of antibodies more quickly.

23
Q

Antibody

A

protein produced by lymphocytes in response to the presence of an appropriate antigen

24
Q

Name the parts of an antibody

A

-Antigen binding site
-Disulphide bridges
-Variable region
-Constant region
-Short chain?
-Long chain?

25
What does the specificity of an antibody depend on?
It depends on its variable regions, which form the antibody binding sites
26
Antibody Variable region
Each antibody has a variable region with a unique tertiary structure (due to different amino acid sequences) thats complementary to one specific antigen
27
Antibody Constant variable
All antibodies have the same constant regions
28
Agglutination
Antibodies bind with antigens, forming antigen-antibody complexes. An antibody has 2 binding sites so it can bind 2 pathogens at the same time . This means pathogens become clumped together (agglutination) Agglutinated bacteria attracts phagocytes which phagocytose many pathogens at once
29
Monoclonal antibodies
Antibodies produced from a single (mono-) clone (group of genetically identical cells) of B cells. This means theyre identical in structure
30
Process of making antibodies (mouse example)
1. Inject mouse with antigen 2. Isolate B lymphocytes 3. Fuse B lymphocyte with a Tumour cell (creates hybridoma) 4. Screen for antibody production 5. Clone 6. Isolate monoclonal antibodies from hybridoma
31
Treatment of cancer
Monoclonal antibodies are used to target drugs to particular types of cells e.g. cancer cells Cancer cells have antigens called 'tumour markers'. You can make monoclonal antibodies that bind to these antigens. Anti-cancer drugs can be attached to the monoclonal antibodies. The drug will only accumulate where there are cancer cells, so side effects with be lower.
32
Positive pregnancy test result stages
1. Any hCG, with its blue beads attached, will bind to the immobilised antibodies, concentrating the hCG-antibody complex with the blue beads attached = blue line 2. Antibodies with blue beads but no hCG attach to the control strip to make sure the test worked.
33
Negative pregnancy test stages
1. No hCG present, so no antigen antibody complexes formed (with antibodies attached to blue beads) 2. There is no hCG to bind to the immobilised antibodies = no colour change occurs in the first line 3. Antibodies with blue beads but no hCG attach to the control strip to make sure the test worked.
34
Pregnancy test, how it works
1. Application area contains antibodies for hCG bound to a blue bead 2. When urine is applied and hCG will bind to the antibody on the beads, forming an antigen-antibody complex 3. The urine moves up the stick carrying any beads with it 4. The test strip contains more antibodies to hCG and so are immobilised
35
Ethical issues related to the use of monoclonal antibodies
1. Mice are used in the production - deliberately inducing cancer in mice 2. Testing new drugs is dangerous - March 2006, 6 volunteers suffered multiple organ failures inn a drug test for monoclonal antibodies 3. Some patients have died from their use in treatment of MS
36
What does ELISA stand for
Enzyme-linked immunosorbent assay
37
What is an ELISA test
-ELISA allows you to see if a patient has any antibodies to a certain antigen, or any antigen to a certain antibody -Can be used to test for roughly anything, including pathogenic infections and allergies
38
How does an ELISA test work
-An antibody is used which has an enzyme attached to it. The enzyme can react with a substrate to produce a coloured product. -The colour change indicated the antigen or antibody is present. In some ELISA tests, the intensity of the colour indicated the quality of the antigen/antibody present
39
Types of ELISA test
-Direct = antigen, antibody, antibody -Indirect = antibody, antigen, antibody
40
Natural active immunity
When you become immune after catching a disease
41
42
Artificial active immunity
A harmless dose of antigen in a vaccine produces memory cells against the pathogen
43
Passive immunity
When you are given antibodies, rather than producing your own
44
Natural passive immunity
E.g. when a baby receives antibodies from its mother through the placenta or breast milk
45
Artificial passive immunity
E.g. When you are injected with antibodies such as anti-venom for a snake bite

Biology (10 decks)

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