Cell Recognition And Immune System

Question 1

What allows the immune system to identify things?

Answer 1

Each type of cell has specific molecules on its surface identify these molecules include proteins and enable the immune systems to identify things

Question 2

What do the protein molecules enable the immune system to identify

Answer 2

Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins

Question 3

Describe non-specific defence mechanism

Answer 3

Response is immediate and the the same for all path

Question 4

Describe specific defence mechanism

Answer 4

Respond to slower and specific to each pathogen

Question 5

Examples of specific and non-specific defence mechanisms

Answer 5

Non-specific
-Physical barrier, e.g. the skin
-phagocytosis

Specific
-Cell mediated response, T lymphocytes
-humoural response, B lymphocytes

Question 6

Define antigen

Answer 6

Proteins on surface of foreign cell

Toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies

Question 7

What protein structure are antigens?

Answer 7

Quaternary structure as it has four polypeptide chains joined together

Question 8

How do b cells respond to foreign antigens?

Answer 8

There’s a variety of B cells a different shapes of receptor

T helper cells activate the cells and simulate them to divide by mitosis

cells with the right shape of receptors for antigen is stimulated to divide

plasma cells secrete antibody

antibodies cause pathogens to clump together this is them harmless and prepare them for destruction

Question 9

Describe the steps of phagocytosis

Answer 9

The phagocyte is attracted to the pathogens by chemoattractants moves towards a pathogen a longer concentration gradient. The phagocyte bind the pathogen.
Lysosomes within the phagocyte migrate towards the phagosome formed by engulfing the bacterium.
The lysosomes release the lyric enzymes where they break down the bacteria.
The breakdown products of the bacteria are absorbed by the phagocyte

Question 10

Define endocytosis

Answer 10

The movement of large molecules into cells using vesicles eg phagocytosis

Question 11

Define exocytosis

Answer 11

Movement of lodge molecules out of cells using vesicles the phago lysosomes fused with the cell membrane and release the debris from the broken down pathogen

Question 12

How do you T cells respond to a foreign antigen?

Answer 12

A phagocyte has engulfed a pathogen and displays the antigen on its surface

The antigen is displayed to many different T cells in the lymph node

Clonal selection -stimulated t cell divide many times

Helper T cells – these secrete chemicals which simulate phagocyte cells stimulate the cells to produce antibodies and activate killer t cells

Killer T cells - these bind to cells presenting the complementary antigen

T memory cells formed after injection

Question 13

Describe perforin

Answer 13

Causes perforation in the cell member and making the self full permanent

Question 14

Describe b lymphocytes

Answer 14

Matures in bone marrow
Involved in humoral immunity
Produce antibodies
Responds to foreign material outside body cells
Responds to bacteria and viruses

Question 15

Describe T lymphocytes

Answer 15

Matures in thyroid gland
involved in cell mediated immunity responsd to foreign material inside body cells
response to cells altered by viruses or cancer to transplanted tissue

Question 16

What protein structure are antibodies?

Answer 16

Quaternary structure proteins (4 polypeptide chain)

Question 17

What are antibodies secreted by?

Answer 17

B lymphocytes eg plasma cells in response to specific antigen

Question 18

What do antibodies bind to ?

Answer 18

Bind specifically to antigens forming antigen antibody complexes

Question 19

How do antibodies lead to the destruction of pathogens ?

Answer 19

Antibodies bind to antigens on pathogens forming an antigen antibody complex (specific tertiary structure so binding site /variable region binds to complementary antigen )

Attract phagocytes

Phagocytes bind to the antibodies and phagocytose many pathogens at once

Question 20

What is a monoclonal antibody?

Answer 20

Antibody produced from genetically identical /cloned B lymphocytes/plasma cells

So have same tertiary structure

Question 21

How can monoclonal antibodies be used in medical treatments?

Answer 21

Monoclonal antibody has a specific tertiary structure/binding site /variable region binds

Complementary to receptor /protein/antigen found only on a specific cell type(e.g cancel cell)

Therapeutic drug attached to antibody

Antibody binds to specific cell forming antigen antibody complex delivering drug

Some mAbs are also designed to block antigens/ receptors on cells

(

Question 22

How can mAbs be used in medical diagnosis?
(E.g pregnancy tests)

Answer 22

mAb has a specific tertiary structure /binding site/variable region

Complementary to specific reception /protein /antigen associated with diagnosis

Dye /stain/fluorescent marker attached to antibody Antibody binds

Antibody binds to receptor/protein/antigen forming antigen antibody complex

Question 23

Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent
assay) test to detect antigens

Answer 23

Attach sample with potential antigens to well
Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
Wash well → remove unbound antibodies (to prevent false positive)
Add substrate → enzymes create products that cause a colour change (positive result)

Question 24

Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent
assay) test to detect antigens
(Sandwich elisa)

Answer 24

Attach specific monoclonal antibodies to well
Add sample with potential antigens, then wash well
Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
Wash well → remove unbound antibodies (to prevent false positive)
Add substrate → enzymes create products that cause a colour change (positive result)

Question 25

Explain the use of antibodies in the ELISA test to detect antibodies

Answer 25

Attach specific antigens to well
Add sample with potential antibodies, wash well
3. Add complementary monoclonal antibodies
with enzymes attached → bind to antibodies if
present
4. Wash well → remove unbound antibodies
5. Add substrate → enzymes create products that
cause a colour change (positive result

Question 26

Suggest the purpose of a control well in the ELISA test

Answer 26

● Compare to test to show only enzyme causes colour change
● Compare to test to show all unbound antibodies have been washed away

Question 27

Discuss some general ethical issues associated with the use of vaccines and
monoclonal antibodies

Answer 27

● Pre-clinical testing on / use of animals- potential stress / harm / mistreatment
○ But animals not killed & helps produce new drugs to reduce human suffering
● Clinical trials on humans- potential harm / side-effects
● Vaccines - may continue high risk activities and still develop / pass on pathogen
● Use of drug - potentially dangerous side effects

Question 28

Explain the differences between the primary & secondary immune response

Answer 28

Primary- first exposure to antigen
○ Antibodies produced slowly & at a lower conc.
○ Takes time for specific B plasma cells to be
stimulated to produce specific antibodies
○ Memory cells produced
● Secondary- second exposure to antigen
○ Antibodies produced faster & at a higher conc.
○ B memory cells rapidly undergo mitosis to
produce many plasma cells which produce
specific antibodies

Question 29

Explain the effect of antigen variability on disease and disease prevention

Answer 29

● Antigens on pathogens change shape / tertiary structure due to gene mutations (creating new strains)
● So no longer immune (from vaccine or prior infection)
○ B memory cell receptors cannot bind to / recognise changed antigen on secondary exposure
○ Specific antibodies not complementary / cannot bind to changed antigen

Question 30

Define vaccine

Answer 30

Injection of antigens from attenuated (dead or weekend) pathogens simulating formation of memory cells

Question 31

How do you vaccines provide protection to individuals against disease?

Answer 31

Specific be lymphocyte with complementary receptor binds to antigen specific T-helper cell binds to antigen-presenting cell and stimulates cell lymphocytes by mitosis to form clones some differentiate into B plasma cells which release antibodies some differentiate into B memory cells on secondary exposure to antigen be memory cells rapidly divided by mitosis to produce B plasma cellsThese release antibodies faster and that’s a higher concentration.

Question 32

Explain how vaccines provide protection for populations against disease

Answer 32

Heard immunity – large proportion of population vaccinated reducing spread of pathogen large proportion of population amuse so they don’t become ill from the infection. Thus there’s fewer infected people to pass on the pathogen/unvaccinated people less likely to come in contact with someone with disease.

Question 33

Describe active immunity

Answer 33

Initial exposure to antigen e.g. vaccine or primary infection memory cells involved antibody produced and secreted by B plasma cells slow takes longer to develop long-term immunity as antibody can be produced in response to specific antigen again

Question 34

Describe passive immunity

Answer 34

No exposure to antigen
No memory cells involved
Antibody introduced from another organism for example, breastmilk/cross placenta from mother
Faster acting
Short term immunity as antibody hydrolysed

Question 35

Describe the replication of HIV in helper T cells

Answer 35

HIV attachment proteins attached to receptors and help a tea cell lipid envelope, fuses of cell surface membrane releasing cap into cell capsule coach releasing RNA reverse transcript reverse transcript convert viral RNA to DNA viral DNA inserted into help a T cell DNA viral protein/captured or produced DNA transcribed into HIV mRNA HIV mRNA translated into new HIV proteins virus particles assembled the released themselves

Question 36

Explain all HIV causes the symptoms of acquired immune deficiency syndrome AIDS

Answer 36

HIV facts and kills helper T cells (host cell) as it multiplies rapidly so so tea helper cells con stimulates toxic, B cells and Fargo sites
so be plasma cells can’t release as many antibodies for a glaciation and destruction of pathogen
immune system deteriorates more acceptable to opportunistic infection Pathogens reproduce, releasing toxins and damage cells

Question 37

Explain why antibiotics are ineffective against viruses

Answer 37

Viruses do not have metabolic processes/ribosomes and viruses do not have bacterial enzymes/Mirin cell wall