immunology

Question 1

state 2 ways that pathogens cause harm/disease?

Answer 1

• pathogen can produce toxins which can directly damage tissue
• pathogen can sometimes replicate inside and destroy host cells

Question 2

def: antigen

Answer 2

a molecule (protein),
which can be recognised as non self by immune system,
stimulates an immune response,
and leads to the production of a specific antibody

Question 3

def: phagocytes

Answer 3

group of white blood cells, can distinguish between cells with or without self antigen

Question 4

non-specific immune system:

Answer 4

1.phagocyte recognises foreign antigens on the pathogen and binds to the antigen
2. pathogen is engulfed by the phagocyte
3. engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle
4. lysosomes fuse with the vesicle releasing lysozymes (hydrolytic enzymes)
5. lyzozymes hydrolyse/digest the pathogen
6. waste materials are removed from the cell by exocytosis
7. phagocyte becomes an antigen presenting cell

Question 5

limitation of non- specific immune response:

Answer 5

takes far too long to destroy the pathogens in an infection,
damage tissue + organs

Question 6

specific immunity:

Answer 6

a specific response to a specific antigen on the surface of a cell or pathogen that has been recognised as non-self

Question 7

what is an antibody?

Answer 7

a globular quaternary protein,
made in response to a specific antigen,
produced by B cells
and secreted by plasma cells

Question 8

where are antigens found and what are their use?

Answer 8

on the cell surface membranes, which are identified as self and non self via these specific antigens

Question 9

name 4 types of foreign antigens

Answer 9

Pathogens - organisms causing disease
Abnormal body cells - cancerous/infected cells
Toxins - poisonous molecules
Cells from other organisms - transplant cells

Question 10

why is phagocytosis part of non-specific immunity?

Answer 10

works the same for any foreign antigen

Question 11

what are phagocytes?

Answer 11

white blood cells which ingest/engulf and destroy any cells presenting a non-self-antigen.

Question 12

what are the cons of phagocytosis?

Answer 12

takes too long and can result in damage to tissues, organs

Question 13

explain phagocytosis

Answer 13

1.Pathogen engulfed by phagocyte
2.Pathogen enters the cytoplasm in a vesicle called phagosome
3.Lysosome fuses with phagosome releasing lysozymes (hydrolytic digestive enzymes)
4.Lysozymes hydrolyse the pathogen and waste materials are released via exocytosis
5.Antigens are presented on the cell membrane making the phagocyte an antigen presenting cell

Question 14

def: specific immunity

Answer 14

responds to a specific antigen on the surface of a cell/ phagocyte which has been recognised as non self

Question 15

what are T-cells

Answer 15

white blood cells with specific receptor proteins on the surface which bind to specific antigens on antigen presenting cells

Question 16

what is the cell mediated
response

Answer 16

involves t-cells

Question 17

what are TH cells (T helper cells)

Answer 17

respond directly to pathogen/antigen or the antigen presenting cells

Question 18

describe the process of T cell clonal selection

Answer 18

1.T helper cell with specific complementary receptor protein binds to antigen on antigen presenting cell becoming activated
2. This then rapidly divides via mitosis producing more T helper cells
3.These clone cells are then differentiated into 3 different types

Question 19

Describe the 3 types of T cells

Answer 19

TH - Specific receptor protein binds to specific antigens releasing cytokines which attracts phagocytes to the area, stimulates specific B cells and activates Tc cells.
T memory cells - remain in the blood in case of re infection
Cytotoxic T killer cells Tc - Locates and destroys virally infected and cancer cells. Binds to antigens and releases perforin which create holes in the cell membrane destroying the cells

Question 20

Why is clonal selection of T cells needed

Answer 20

Not enough room in body for lots of T cells to be stored, and would increase total energy demands of organism so instead are cloned on demand

Question 21

Explain the humoral response

Answer 21

1.Specifc THcell releases cytokines when bound to specific antigen stimulating specific B cell
2.Specific B cell undergoes rapid mitosis producing clones
3.These then differentiate into B plasma and B memory cells

Question 22

Explain the function of B plasma cells

Answer 22

Produce and secrete large amounts of specific antibodies into the blood plasma

Question 23

Explain the function of B memory cells

Answer 23

Remain in blood stream to rapidly respond to pathogens if re-infection occurs.
They are rapidly activated by cytokines and more quickly cloned by mitosis into plasma cells and more b cells
These plasma cells then produce higher concentrations of antibodies at a quicker rate

Question 24

What is the secondary response

Answer 24

Activation of memory cells to produce antibodies more quickly and in higher
concentrations, eliminating the antigen before symptoms develop

Question 25

Draw and label the structure of an antibody

Answer 25

Globular quaternary protein made of 4 polypeptide chains
Main part is a constant region. The variable regions have a different primary structure therefore a different tertiary structure making the binding sites for antigens specific and complementary. This allows antigen antibody complexes to form
Disulphide bridges in the base of heavy chain, variable region is light.

Question 26

Describe 2 ways in which antibodies aid immune
response

Answer 26

Agglutination - Each antibody has 2 binding sites. Specific antibodies bind to specific antigens on pathogens clumping them together. This attracts phagocytes to destroy many pathogens at once
Opsonisation - Antibodies mark pathogens so phagocytes can recognise and destroy pathogens more efficiently

Question 27

Explain how lysis and antitoxins/antivenom aid the immune svstem

Answer 27

Lysis - antibody binds to antigen and destroys pathogen membrane
Anti-venom - Binds to venom/ toxins and causes its destruction.
May also prevent their replication and prevent them binding to target receptors

Question 28

Compare the primary and secondary response

Answer 28

Primary exposed to antigen for first time, not many t or b cells. Symptoms of disease shown, antibodies slowly produced and t memory cells.
Secondary clonal selection occUrs faster from t memory cells and b cells and more antibodies are more rapidly produced, no symptoms show.

Question 29

When is the secondary response effective

Answer 29

If pathogens have the same antigens on their surface as they can be recognised by b memory cells

Question 30

Explain antigenic variability

Answer 30

Antigens on the surface of pathogens can mutate. This means primary structure is different, resulting in a different tertiary structure which means the antigen has a different shape. It will not be recognised by the b memory cells and it is no longer complementary to the receptor proteins

Question 31

How can vaccines be developed to overcome antigenic variability

Answer 31

Use all of the different strains of a pathogen to produce a range of different antibodies to the different mutated antigens

Question 32

Explain the differences between active and passive immunity

Answer 32

Passive - no antigen exposure, no memory cells produced, short term protection as antibodies get broken down, immediate protection, antibodies received from elsewhere e.g.
breast milk/placenta

Question 33

Explain how vaccines are made

Answer 33

1.Dead/weakened antigen from pathogen injected into body and macrophage presents antigen on its cell membrane
2.T-cells with complementary receptor protein binds to antigen releasing cytokines
3.This stimulates specific b cell to rapidlv divide by mitosis
4.This produces plasma b cells which secrete antibodies in large numbers and memory b cells which remain in blood 5.1f antigens present again, plasma cells more rapidly produced and produce more antibodies quicker and in higher concentrations

Question 34

What is herd immunity

Answer 34

If majority (85%+) population vaccinated there is little chance for disease to spread even to non-vaccinated as less people to pass it on

Question 35

What are 3 side effects to vaccines

Answer 35

1.Complications/unexpected health problems
2.If taken orally enzymes may break down in gut, or molecules may be too large to be absorbed into blood
3.Boosters needed to ensure more memory cells are produced

Question 36

Give 5 ethical issues to vaccines

Answer 36

1.Must be tested on animals first
2.Must also be tested on humans
3.Economic/affordability issues
4.Risks vs effectiveness
5.Herd immunity - unfair

Question 37

What are monoclonal antibodies

Answer 37

Antibodies with same tertiary structure cloned from the same plasma cell which bind specifically to one antigen

Question 38

What are 5 uses of monoclonal antibodies

Answer 38

1.Research
2.Immunoassays
3.Diagnosis
4.Targeting drugs to specific cell types
5.Killing specific cells

Question 39

What is an ethical issue to monoclonal antibodies

Answer 39

Involves tumour cells in mice and human volunteers with unexpected side effects

Question 40

What is the Elisa test used for

Answer 40

To test if a patient has
antibodies to a certain antigen or vice versa, and to test for pathogenic infections

Question 41

Explain the direct Elisa test

Answer 41

1.Antigens bound to inside of the well
2.complementory antibody to antigen added
3. 2nd antibody with enzyme attached added
4. Washed to remove unbound antibodies
5.substrate solution added which changes colour if antigen present

Question 42

Explain how the Elisa test is used for HIV

Answer 42

1.HIV antibodies bound to bottom of testing well
2.Blood sample containing many antigens added
3. Any specific antigens bind to antibodies becoming immobilised
4.Wash solution and add second antibody with enzyme attached
5.Binds to any complementary antigens
6.wash so any unbound enzyme antibodies washed away
7.Add substrate solution, colour change indicates HIV positive

Question 43

Describe the structure of HIV

Answer 43

Lipid viral envelope (X2) , attachment proteins, Reverse transcriptase and RNA inside the capsid

Question 44

What does HIV do

Answer 44

Effects the immune system by infecting and killing T helper cells compromising cell mediated immunity

Question 45

Explain the process of HIV replication

Answer 45

1.Attachment protein on HIV binds to receptor molecule on
TH cell
2.Capsid fuses with cell membrane and is released into the cell, uncoating and releasing Viral RNA and enzymes
3.Reverse transcriptase makes complementary DNA from
RNA template using host nucleotides which is then made double stranded
4. The viral cDNA moves into TH cell nucleus and is inserted into host cell’s DNA. Person is now infected
5.The viral DNA is then transcribed into viral mRNA to produce HIV proteins… 6.These proteins are assembled into new
HIV viruses and break away from T cell which forms the lipid envelope with TH receptors embedded.
7.The t cell then ruptures and dies

Question 46

Give 5 ethical issues to vaccines

Answer 46

1.Must be tested on animals first
2.Must also be tested on humans
3.Economic/affordability issues
4.Risks vs effectiveness
5.Herd immunity - unfair

Question 47

What are 3 side effects to vaccines

Answer 47

1.Complications/unexpected health problems
2.If taken orally enzymes may break down in gut, or molecules may be too large to be absorbed into blood
3.Boosters needed to ensure more memory cells are produced

Question 48

Describe how AIDS develops

Answer 48

1.A high viral load leads to large destruction of TH cells
2.There is less activation of B cells and T cells
3.Less plasma cells and antibodies produced
4.Less able to destroy other pathogens/ mutate cells/cancer cells
5.Secondary infections develop

Question 49

Give 2 ways aids is diagnosed

Answer 49

1.Symptoms of secondary infections
2.Lack of T helper cells

Question 50

Why can aids not be detected by antibodies

Answer 50

not a pathogen

Question 51

How do antibiotics attack bacteria

Answer 51

Prevent bacterial cell wall forming by attacking 70s ribosomes
No cell wall means unable to resist osmotic pressure, cell bursts due to too much water entering via osmosis.

Question 52

Why are antibiotics not effective against viruses

Answer 52

Viruses have no organelles to disrupt as they use host cell to replicate and carry out metabolic activity. They also have a capsid instead of cell wall and spend most time in host cell so hard to target.