Immunology

Question 1

how does the immune system distungiush cells between “self” and “non-self”

Answer 1

antigens

Question 2

what is the definition of an antigen

Answer 2

a foreign molecule, usually a protein, that stimuluates an immune response

Question 3

True or False

Antigens have a specific shape and tertiry structure that is complementary to an anitbody

Answer 3

True

Question 4

what is the non-specific immunity response

Answer 4

phagocytes

Question 5

explain the process of phagocytosis

Answer 5

• phagocytes move to the site of infection and engulf the pathogen. This forms a vesicle known as a phagosome
• phagocytes contain many lyosomes which fuse with the phagosome
• the hydrolytic enzymes called lysozymes in the lyosome hydrolyse the pathogen

Question 6

explain the process of antigen presentation

Answer 6

• after phagocytosis they display part of the pathogen on its cell surface membrane
• this allows activation of other immune cells such as T and B cells

Question 7

what is the specific immune reponse

Answer 7

involves immune cells becoming activated in response to presence of a specific antigen of a pathogen

Question 8

what does antigen presentation initiate

Answer 8

the cellular response

Question 9

T helper cells

explain the first process of the cellular response

Answer 9

• they have a receptor that has a complementary shape to the specific antigen
• upon binding to the antigen, the T helper becomes activated and divides by mitosis

Question 10

the activated T helper cells release ——-

Answer 10

cytokines

Question 11

explain what cytokines do

Answer 11

• stimulate B cells to divide by mitosis
• stimulate phagocytes
• stimulates cytotoxic T cells

Question 12

explain the role of cytotoxic cells

Answer 12

• contain receptors which bind to antigens on the surface of either virally infected or cancerous cells
• the cytotoxic cells then release perforin which makes holes in the cell surface membrane of the cell
• this leads to the cell undergoing apoptosis (cell death) and being destroyed

Question 13

involves antibodies

explain the humoral response

Answer 13

• B cells are stimulated directly by the antigen binding to the receptors
• or stimulayed indirectly by the release of cytokines
• upon stimulation, the B cells divide by mitosis to produce clones
• some of these B cells differentiate into plasma cells which produce and release large quantities of monoclonal antibodies. This is the primary response
• some B cells become memory cells. This is the secondary response

Question 14

explain the structure of an antibody

Answer 14

• quaternary protein where 4 polypeptide chains are joined together by disulphide bridges

Question 15

what happens when an antibody binds to its antigen

Answer 15

an antigen-antibody complex is formed

Question 16

what is agglutination

Answer 16

• antibodies bind to antigens
• they clump them together
• this marks the antigens and helps attract phagocytes

Question 17

what do vaccines contain

Answer 17

• dead or weakened form of the pathogen
• specific antigen

Question 18

explain how vaccines make use of the primary and secondary response

Answer 18

• the stimulation of B cells will lead to the differentiation into plasma cells and the production of antibodies -primary response
• memory cells are also produced - secondary response

Question 19

explain herd immunity

Answer 19

• vaccinated individuals recover from an infection quickly
• therefore less likely to spread the pathogen to unvaccinated individuals

Question 20

explain the steps of ELISA test

Answer 20

1. monoclonal antibodies are fixed to the bottom of the test well
2. a sample, potentially containing the antigen, is added to the well and will bind to the antigen-binding site on the antibody
3. the well is washed with water
4. a second monoclonal antibody is now added - which is attached to an enzyme - and will bind to another part of the antigen if present
5. the well is washed again
6. a substrate is added and the enzymes on the second monoclonal antibody will convert this to a different colour
7. the colour change is a positive result

Question 21

give 4 key features of HIV

Answer 21

• RNA genome
• contains reverse transcriptase
• genome is surrounded by a protein coat called capsid
• the lipid envelope contains attachment proteins

Question 22

explain the replication of HIV

Answer 22

1. attachment proteins on HIV bind to specific receptors on T helper cells
2. viral RNA and reverse transcriptase enter the cell
3. the reverse transcriptase converts viral RNA into DNA
4. the viral DNA moves into the nucleus and is inserted into the host cell genome
5. transcription of HIV DNA into HIV mRNA which is translated to produce HIV proteins
6. the infected T helper cells starts to assemble new virus particles
7. virus particles are released from the T helper cell

Question 23

how do antibiotics work

Answer 23

• they prevent bacteria from synthesising murein cell wall
• directly damage the cell wall