immunology

Question 1

state 2 ways pathogens can cause harm/disease?

Answer 1

• bacteria releases toxins that directly damage tissue
• pathoigens replicate inside and destroy host ells

Question 2

define an antigen

Answer 2

• molecule that stimulates an immune response
• results in the production of a specific antibody

Question 3

examples of antigens

Answer 3

glycoproteins
glycolipids

Question 4

retrovirus

Answer 4

virus with single stranded RNA

Question 5

describe the non specific immune defence mechanism the body may launch against pathogens

Answer 5

phagocytosis
- pathogen is engulfed by the phagocyte
- engulfed pathogen enters cytoplasm in a vesicle (phagosome)
- lysosomes fuse with phagosome, releasing hydrolytic enzymes (lysozymes)
- lysozymes break down/hydrolyse the pathogen
- waste materials ejected via exocytosis
- phagocyte presents antigens on csm

Question 6

describe how a pjhagocyte destroys a pathogen present in the blood

Answer 6

• engulfs
• forms a vesicle
• lysosome fuses with vesicle
• enzymes hydrolyse

Question 7

give 2 other types of cells, other than pathigens, that stimulate an immune response

Answer 7

• cells from other organisms
• cancer/abnormal cells
• cells infected by viruses

Question 8

cellular response

Answer 8

• phagocyte presents antigen on csm
• T helper cell with a specific receptor binds to antigen, activating it
• rapidly divides by mitosis
• produces many T Helper cells with specifically complementary antigens

Question 9

when a vaccine is given to a person, it leads to the production of antibodies against a disease causing organism. describe how.

Answer 9

• vaccine contains antigen from pathogen
• phagocyte presents antigen on csm
• t helper cell with specifically complementary receptor binds to the antigen
• t cell stimulates the b cell with a complementary antibody on its surface
• b cell divides by mitosis
• produces same antibody
• b cells secrete large amounts of antibody

Question 10

what is the role of the t helper cell

Answer 10

• binds to APC
• releases cytokines that attract phagocytes to area
• releases cytokines that activate cytotoxic killer T cells (Tc)
• activates specifically complementary b cell
• form memory Th Cells

Question 11

what is the role of cytotoxic killer t cells

Answer 11

• destroys infected body cells presenting antigen
• binds to APCs
• releases perforin which creates holes in csm, destorying APC

Question 12

explain how the humoral response leads to immunity

Answer 12

• b cells specific to the antigen reproduce by mitosis
• b cells produce plasma and memory cells
• second infection produces antibodies in a larger quanitity and quicker

Question 13

antibody

Answer 13

proteins made in response to antigens
- binding sites bind specifically to antigen
- specific antibody produced by a specific plasma cell

Question 14

antibody structure

Answer 14

• 4 structure, 4 polypeptide chains, Y shaped
• variable region has different primary structure and didfferent 3 structure

Question 15

describe and explain the role of antibodies in stimulating phagocytosis

Answer 15

• bind to antigen
• cause clumping

Question 16

how do antibodies assist in the destruction of pathogens?

Answer 16

• aggultination: clump pathogens together after binding to antigens
• opsonisation: mark pathogens so phagocytes recognise and destroy pathogens more easily
• binds to toxins
• prevent pathogens replication

Question 17

secondary response

Answer 17

• activation of memory cells to produce antibodies
• second is rapid and extensive
  “ more antibodies are produced more rapidly”

Question 18

antigenic variability

Answer 18

antigens mutate or change shape
eg: flu, HIV
- difficult to develop vaccines against it
- not recognised by memory cell, no 2ndary response

Question 19

describe the difference between active and passive immunity

Answer 19

active vs passive
- memory cells vs no memory cells
- production of antibodies via plasma cells vs passive involves antibody introduced from some outside source
- active long term because antibody produced in response to antigen
- passive short term because antibody broken down
- active takes time vs passive fast acting

Question 20

state why some antibodies are referred to as monoclonal

Answer 20

• produced from the same plasma cell
• countet the same specific antigen

Question 21

tests using monoclonal antibodies are specifc. use your knowledge of protein structure to explain why.

Answer 21

• specific primary structure
• specific tertiary structure
• specifically complementary to one antigen

Question 22

vaccinations

Answer 22

• contain dead, weakened pathogens
• some may cause side effects

Question 23

herd immunity

Answer 23

if enough people are vaccinated, little chance of disease spreading
- even nonvax will be protected

Question 24

uses of monoclonal antibodies

Answer 24

• resesarch
• pregnancy tests/ ELISA tests
• targetting drugs
• killing specifc cells

Question 25

elisa test

Answer 25

monoclonal antibody fixed to surface of test well - sample binds to antibody due to complementary shape - second monoclonal antibody (with enzyme attached) added, binds to molecule - washed so any unbound antibodies with enzyme are washed away - substrate added, colour change=positive result

Question 26

describe the role of antibodies in producing a positive test result in an ELISA test

Answer 26

- first antibody complementry to antigen - second antibody with enzyme attached is added - second antibody attaches to antigen - solution added and colour change

Question 27

describe the structure of the human immunodeficiency virus (HIV)

Answer 27

- RNA as genetic material - reverse transcriptase - protein capsid - phospholipid envelope - attachment proteins

Question 28

HIV replication

Answer 28

- protein on HIV binds to protein found on T helper cells - capsid fuses with csm and releases viral RNA and enzymes into helper T cell - HIV's reverse transcriptase converts viral RNA into cDNA using host nucleotides - viral cDNA inserted into host genome in nucleus. - person now infected - transcription of viral DNA into viral RNA which is translated to produce HIV proteins - reduction in number of Th cells over time

Question 29

How can AIDS be detected?

Answer 29

checking number of T helper cells 200 Th cells in AIDS and 800-1200 Th uninfected - compromises immune system so secondary infections more vulnerable to kill

Question 30

describe how a person infected with HIV will develop AIDS and die of secondary infections

Answer 30

- high viral load leads to increase in destruction of T hekper cells - less activation of B cells - Less production of plasma cells/antibodies - more able to destroy other pathogens

Question 31

why dont antibiotics work on viruses?

Answer 31

- prevent bacteria making a normal cell wall by targetting 70s ribosomes - unable to resist osmotic presure, cells burst due to increase cell volume of water by osmosis - viruses have capsid - spend time in host cell so out of reach