5 - Immunity

Question 1

Are what some primary defences on the body?

Answer 1

Mucus in the nose and throat - traps pathogens, ciliated epithelial cell ‘wafts’ this up to form phelgm which is coughed out.
Goblet cells - traps particles and pathogens
Stomach acid - pH7 so acidic that enzymes in pathogens are denatured
Skin - acts as a physical barrier, also produced sebum from sebacious glands
Eyes - tears cleanse eyes and contain lysosome, an enzyme
Vagina - acidic, contains lactic acid

Question 2

Structure of a virus

Answer 2

Envelope protein - has an attachment protein to allow attachment to the host cell for replication
Capsid - nucleic acid protein coat
Nucleocapsid - capsid + viral genome
Viral tegument - cluster of proteins specific to the function of that virus

Question 3

What are antigens

Answer 3

Antigens are on the cell surface membrane allow cells to identify hemself as self cells to protect against lymphocytes.

Question 4

What is a pathogen?

Answer 4

A disease causing microorganism

Question 5

What are the types of pathogen?

Answer 5

Virus
Protist
Fungi
Bacteria

Question 6

What are the steps to phagocytosis?

Answer 6

1 - phagocyte recognises antigens on pathogen
2 - phagocyte binds to pahtogen
3 - cytoplasm of phagocyte engulfs the pathogen
4 - pathogen contained in a phagocytic vacuole aka a phagosome
5 - lysosomes digest pathogen and absorbs digestive products
6 - phagocyte presents pathogens antigen, becomes an antigen presenting cell

Question 7

What are the affects of phagocytosis?

Answer 7

Inflammation at the site of infection, the swollen areas contain dead pathogens and phagocytes, this build up is known as ‘pus’, this inflammation is a result of histamine being released

Question 8

Where are T cells produced and matured

Answer 8

Bone marrow, matured in the thymus gland

Question 9

The role of T-cells

Answer 9

• Pathogen = engulfed by phagocyte, this is a non-specific process
• phagocyte displays pathogen’s antigen on cell surface
• specific t cell receptor fits onto antigens, the attachment activates T-cells to divide by mitosis, forming clones
• cloned t cells develop memory cells which: stimulate phagocytes to act, stimulate b-cells to produce antibodies and activate cytotoxic t-cells

Question 10

How do lymphocytes recognise our own cells?

Answer 10

• In foetus: protected by placenta & mother’s immunity
• Any developing lymphocytes that could potentially attack embryo’s self cells are destroyed
• In adults, lymphocyes ate made in the bone marrow and any developing lymphocytes that could potentially attack self cells are destroyed, the resulting lymphocytes mature in the thymus gland

Question 11

How are T-cells distinguishable from other lymphocytes?

Answer 11

They have a TCR on the cell surface

Question 12

How do cytotoxic T cells work?

Answer 12

1- Tc cell binds to infected cell on the antigen
2 - Perforin makes holes in infected cells membrane and enzyme enters
3 - Enzyme promotes apoptosis
4 - Infected cell is destroyed.

Question 13

What is apoptosis?

Answer 13

programmed cell death

Question 14

What is cell mediated immunity?

Answer 14

responses from cells such as : phagocytes, T-cells, cytotoxic T-cells

Question 15

What is humoral immunity?

Answer 15

Immunity relating to bodily fluids, for example: B cells in the blood

Question 16

B Cells/ B lymphocytes ((2))

Answer 16

• Produced in bone marrow
• Covered in antibodies, each have a different antibody on their membrane, different antigens bind to complimentary shaped antigens

Question 17

Stages of B cell response

Answer 17

1- B cell binds to complimentary antigen
2 - B cell acvtivated to divide by mitosis: creates plasma cells
3 - Plasma cells produce antibodies
4 - Antibodies bind to pathogen and destroy them
5 - Some B cells can develop into memory cells

Question 18

Memory cells

Answer 18

• Live longer than plasma cells
• Do not produce antibodies
• Circulate in blood/ tissue fluid
• If they encounter the same antigen @ a later date, they rapidly divide into more plasma cells & more memory cells

Question 19

What are MABs

Answer 19

Monoclonal Antibodies
antibodies produced from a single group of geneticall identical B cells

Question 20

How are MABs produced

Answer 20

1- Expose mouse to non-self antigens, so it produces B-cells which produce the antibodies required
2- Spleen Cells which produce the lymphocytes are removed

Question 21

What are the two types of regions in antibodies?

Answer 21

Variable Regions and Constant Regions.
Variable Regions have a unique tertiary structure to bind to complementary antigens, while Constant Regions allow binding to receptors on the immune system.

Question 22

What is the structure of antibodies?

Answer 22

Made from 4 polypeptide chains: 2 Light Chains and 2 Heavy Chains. The quaternary structure is connected by disulphide bridges.

Question 23

How many antigens can one antibody bind to at once?

Answer 23

2 antigens

Question 24

What is the process called when antibodies cause pathogens to clump together?

Answer 24

Agglutination. This process makes it easier for phagocytes to engulf multiple pathogens at a time.

Question 25

What is the function of antibodies in neutralizing?

Answer 25

Neutralizing toxins released by pathogens

Question 26

How do antibodies prevent viruses from entering host cells?

Answer 26

By binding to viruses and blocking their entry. Viruses have protein spikes that recognize and bind to host cell receptors.

Question 27

What is antigenetic variability?

Answer 27

The formation of different strains of pathogens due to mutations in genetic material. This results in different antigens that are not recognized upon reinfection.

Question 28

Why is antigenetic variability significant for vaccines?

Answer 28

Commonly varied pathogens have vaccines effective only against the recent strain circulating. This is particularly true for pathogens like Influenza and HIV.

Question 29

What are the functions of antibodies?

Answer 29

- Agglutination - Neutralising toxins released by pathogens - Prevention of Viruses Entering host cells

Question 30

Explain how to carry out an ELISA test

Answer 30

- select antibodies complimentary to the antigen and add to the reaction vessel - collect the sample from the patient and add to the reaction vessel - complimentary antibodies will bind to antigens on pathogen if present - wash the sample to eliminate unbound antigens from the sample - add another complimentary antibody with an enzyme attached, if pathogen is present, antibody with enzyme attached will bind to antibody boound to antigen - wash sample again to avoid false positive - add the substrate for the enzyme, +ve results show a colour change as present enzyme breaks down substrate

Question 31

How do pregnancy tests work?

Answer 31

- urine of a pregnant woman contains hCG hormone - urine with hCG moves along test strip - hCG binds to complimentary mobile antibodies with coloured dye attached - urine carries hCG antibody complexes to immobile antibodies, these attach and release the dye, causing a +ve result

Question 32

How does herd immunity work?

Answer 32

- when enough people get a vaccine, there is herd immunity as not many people can spread the disease as they do not demonstrate symptoms, this protects a wider amount of people

Question 33

How does HIV replicate?

Answer 33

- Attachment proteins on HIV bind complimentary receptors on a helper T cell - RNA and reverse transriptaste enter cell as protein capside fuses with cell membrane - Reverse transcriptase converts viral RNA to DNA - viral mRNA is produced through transcription - viral proteins are produced via translation - these proteins produced are used to assemble a new HIV particle which then leaves the T helper cell and the process repeats - When the process is done, the T helper cell is destroyed

Question 34

How does HIV develop into AIDS?

Answer 34

HIV uses T helper cells as a host cell for viral replication. When the process is done, the T helper cell is destroyed, continued replication results in the destruction of many T helper cells. - This means there are less B cells activated and therefore less antibodies produced - This means there are less cytotoxic T cells stimulated, so less infected cells are killed.

Question 35

What is active immunity?

Answer 35

The body makes antibodies after ebing exposed to an antigen.

Question 36

What is natural active immunity?

Answer 36

- the body becomes immune after infection as the natural immune response and production of antibodies. - this allows for long term protection as memory cells are produced

Question 37

What is artificial active immunity?

Answer 37

- the body becomes immune after being given a vaccination containing a harmless dose of the antigen, the immune system produces antibodies - this allows for long term protection as memory cells are produced

Question 38

What is passive immunity?

Answer 38

- the body is given antibodues that have been made by a different organism

Question 39

What is natural passive immunity?

Answer 39

e.g baby gets antibodies from mother from placenta and breastmilk, this only produces a short term protection as no memory cells are produced and antibodies are broken down by spleen evetually

Question 40

What is artificial passive immunity?

Answer 40

- You are injected with antibodies (e.g - tetanus vaccine) - Short time protection as no immune response, no memory cells are produced.

Question 41

What do vaccines do

Answer 41

- introduces antigens of a dead/ weakened pathogen to the body to stimulate the production of antibodies and memory cells - often contain multiple strains (multiple antigens)

Question 42

How does the amount of doses of a vaccine correlate to the amount of memory cells?

Answer 42

- One dose = primary immune response - Multiple doses = secondary response (increases no. of mem cells and antibodies)

Question 43

What are the available methods for making pathogens harmless in vaccines?

Answer 43

- killing pathogen but leaving antigens unaffected - weaken pathogen but leave antigens intact - purified antigens removed from the pathogen - toxoids (inactivated toxins) = trigger the same immune system