5 - Cell Recognition and the Immune System

Question 1

non-specific defense mechanisms

Answer 1

IMMEDIATE AND THE SAME FOR ALL PATHOGENS
barriers to entry - skin, mucus, stomach acid
phagocytosis

Question 2

specific defense mechanisms

Answer 2

SLOWER AND SPECIFIC TO EACH PATHOGEN

lymphocytes release specific antibodies for specific pathogens

Question 3

phagocytosis

Answer 3

phagocyte is attracted to pathogen by foreign antigens on pathogen
pathogen engulfed by phagocyte
pathogen enclosed in phagosome
lysosome fuses with pahgosome
lysosome contains lysozymes/enzymes
lysozymes/enzymes hydrolyse pathogen

Question 4

antigen

Answer 4

a molecule that is recognised as non-self and triggers an immune response by lymphocytes

Question 5

B lymphocytes

Answer 5

mature in bone marrow

associated with HUMORAL immunity

Question 6

T lymphocytes

Answer 6

mature in thymus gland

associated with CELLULAR immunity

Question 7

cellular/cell-mediated immunity

Answer 7

1. an antigen-presenting cell is present
2. a specific T helper cell has receptors that are complementary to the presented antigens
3. attachment stimulates division of T cell by mitosis
4. clone of genetically identical T cells form
5. these T cells develop into memory cells, stimulate phagocytosis, stimulate B cells to divide and secrete antibody, activate cytotoxic T cells

Question 8

cytotoxic T cells

Answer 8

produce a protein called perforin which makes holes in the cell surfac membrane
holes make the membrane freely permeable to all substance and cell dies as a result

Question 9

memory cells

Answer 9

responsibel for secondary immune response

circulate in blood and tissue fluid in readiness to respond to future infection by the same pathogen

Question 10

humoral response

Answer 10

1. surface antigens of a pathogen are taken up by a B cell, it processes and presents them on its membrane
2. helper T cell attaches to the antigens on the B cell, activating the B cell
3. B cell divides by mitosis to give a clone of plasma cells
4. cloned plasma cells produce and secrete the specific antibody that exactly fits the pathogen’s antigen
5. the antibodies attach to the antigens on the pathogens and destroy them
6. some B cells develop into memory cells

Question 11

antibody

Answer 11

a protein produced by lymphocytes in response to the presence of a particular antigen
cause agglutination of pathogens which makes it easier for phagocytes to locate them
serve as markers that stimulate phagocytes to engulf

Question 12

structure of antibody

Answer 12

2 identical binding sites which are complementary to a specific antigen
made up of 4 polypeptide chains - pair of longer heavy chains, pair of shorter light chains

Question 13

monoclonal antibodies

Answer 13

antibodies produced by a single clone of cells

Question 14

direct monoclonal antibody therapy

Answer 14

monoclonal antibodies that are specific to the antigens on cancer cells are produced
antibodies given to the patient and they attach themselves to the cancer cell receptors
blocks the chemical signals that stimulate their uncontrolled growth

Question 15

indirect monoclonal antibody therapy

Answer 15

a radiactive/cytotoxic drug is attached to the antibody

when the antibody attaches to the cancer cell it kills it

Question 16

active immunity

Answer 16

inducing an immune response and the production of antibodies (natural and acquired)

Question 17

passive immunity

Answer 17

immunity which is acquired from the introduction of antibodies into individuals (eg. across the placenta during pregnancy)

Question 18

success of a vaccination programme relies on

Answer 18

economic availability
few side effects
availability of transport, storage, production and administration
ability to produce HERD IMMUNITY

Question 19

herd immunity

Answer 19

sufficiently large proportion of population has been vaccinated to make it difficult for a pathogen to spread within a population

Question 20

ethical issues with vaccines

Answer 20

production and development often uses animals
may have side-effects causing long term harm
testing on humans?
individual health risk
ethically right to be compulsory?

Question 21

HIV

Answer 21

human immunodeficiency virus - a retrovirus

Question 22

retrovirus

Answer 22

a virus that has the ability to convert RNA into DNA using reverse transcriptase

Question 23

replication of HIV

Answer 23

• HIV binds to a helper T cell and fuses with its membrane
• contents of HIV are released into cell
• reverse transcriptase from HIV converts the virus’ RNA into DNA
• DNA travels into the helper T cell nucleus and provides the instructions which cause the T cell to produce HIV components
• components move together to form HIV particles
• HIV particles leave the T cell with a section of the T cell membrane enclosing it

Question 24

how HIV causes symptoms of AIDS

Answer 24

specifically attacks helper T cells, T cells die because of production of HIV within them, causes lack of T cells in body, problems in fighting infection (cannot stimulate production of B cells to produce antibodies), secondary infections cause death

Question 25

ELISA test

Answer 25

1. apply sample to a well
2. wash the surface several times to remove any unattached antigens
3. add the antibody to the well which is specific to the antigen you are trying to detect
4. the antibodies will bind to any of the specific, complementary antigen if present in the sample
5. wash the well to remove unbound anitbodies
6. add a second antibody that can bind to the first antibody, and has an enzyme attached
7. wash the well to remove any unbound antibodies
8. add a solution of the substrate of the enzyme
9. if the second antibody is present the enzyme associated to it will act on the solution to give a coloured product
10. amount of antigen present is relative to the colour intensity of the solution

Question 26

bacterial cells do not burst due to osmosis because…

Answer 26

their cell wall is made of murein