5.Cell Recogniton And The Immune System

Question 1

What is an infection

Answer 1

The interaction between a pathogen and the body’s defense mechanisms

Question 2

What’s immunity

Answer 2

The means by which the body prot cts itself from infection

Question 3

What are the two types of defence mechanisms

Answer 3

Non specific - phagocytes and physical barriers

Specifics-humoral response and cell mediated response

Question 4

What things do protein molecules allow immune systems to recognise

Answer 4

Pathogens
Abnormal cells
Non self material
Toxins

Question 5

How are transplant rejection slimited

Answer 5

Immunosuppressants are used and donor tissues are matched as closely as possible

Question 6

How self material is recognised

Answer 6

In foetus lymphocytes constantly collide with self material
Infections are rare
Some lymphocytes have receptors that fit body cells, these underdogs apoptosis or are suppressed, the remaining lymphocytes only fit foreign material

In adults bone marrow lymphocytes only encounter self antigens if they recognise em they undergo programmed cell death before they can differentiate

Question 7

What is phagocytosis

Answer 7

1-chemical products from pathogen attract phagocyte
2-receptors of c.s.m of phagocyte recognise and bind to chemical son surface of pathogen
3-phagocyte engulfs by endocytosis to form vesicle called phagosome
4-lysosomes fuse with phagosome forming phagolysosome
5-lysosomes releases their lysozymes into vehicle where they hydrolyse cell wall of pathogen
6-products either absorbed or released by exocytosis

Question 8

What is an antigen

Answer 8

proteins of c.s.m or cell wall (cell surface membrane) recognised as non self by immune system and stimulates immune response

It’s presence triggers production of antibodys

Question 9

What is a lymphocyte

Answer 9

A white blood cell involved in the specific immun response

Produced in bone marrow by stem cells

Question 10

What are B lymphocytes

Answer 10

Mature in bone marrow
Associated with humoral response
Involves antibodies present in body fluid or blood plasma

Question 11

What are T lymphocytes

Answer 11

Mature in thymus gland

Associated with cell mediated response, involves body cells

Question 12

What is the cell mediated immunity

Answer 12

1-Phagocyte hydrolysis pathogen, presents its antigen on MHC complex on surface membrane
2-Specific t helper cell binds to antigen
3-attachment activates T cell, T cell divides rapidly by mitosis and form clones
4-cloned cells develop into memory cells, stimulate phagocytosis, stimulate B cell division, activate cytotoxic t cells

Question 13

How do cytotoxic T cells kill infected cell,s

Answer 13

Produce perforin
Makes holes in cell surface membrane
Cell membranes freely permeable
Cell dies due to lysis

Question 14

What is the humoral response

Answer 14

1-B cell takes in surface antigen of invading pathogen
2-B cell processes and presents antigen on c.s membrane
3-Helper T cell binds to processed antigen
4-B cell activated to divide by mitosis form plasma cell clones
5-cloned plasma cells produce and secrete specific antigen for antig n
6-antibodies bind to and destroy antigens
7-some B cells form memory cells(rapidly divide and can develop into plasma cells in future)

Question 15

What are anti bodies

Answer 15

Synthesised by B cells
Specific binding sites
Made of 4 polypeptide chains
Two pairs-heavy chain and light chain 
Antibody antigen complex-binding site called variable region

Question 16

How do antibodies lead to destruction of antigen

Answer 16

1-agglutination or bacterial cells, clumps of cells, easier for phagocytes to locate
2-markers that stimulate phagocytes to engulf bacterial cells they are attached to

Question 17

What are monoclonal antibodies

Answer 17

Made by identical immune cells, all clones of one parent cells, all identical to one another

Question 18

How are monoclonal antibodies used in targeting medication (direct monoclonal antibody therapy)

Answer 18

Eg herceptin on breast cancer
Monoclonal antibody given to patient
Antibodies bind to antigens on cancer cells
Attach to surface, and block chemical signals that stimulate the uncontrolled growth

Question 19

What is indirect monoclonal antibody therapy

Answer 19

Radioactive or cytotoxic drug attached to monoclonal antibodies
Monoclonal antibodies given to patient
When they attach to cancer cell, it kills them.
Small dose used as very specific

Question 20

How are monoclonal antibodies used in medical diagnosis

Answer 20

Eg prostate cancer
Monoclonal antibodies interacts with cancers antigens, then PSA levels obtained
Higher levels will suggest further tests are needed

Question 21

How are monoclonal antibodies used in pregnancy testing

Answer 21

Hormone produced by placenta HCG found in urine
Monoclonal antibodies on test strip are blinded to blue bead
HCG antibody colour complex moves along strip until trapped by another antibody creating coloured line

Question 22

Ethics of monoclonal antibodies

Answer 22

Production involves mice-make tumours is deliberate and inhuman
Used successfully in treating diseases but also deaths
Testing for new drugs-causes issues eg 7 patients underwent organ failure

Question 23

What’s passive immunity

Answer 23

Introduction of antibodies from outside source 
No direct contact with pathogen 
Immunity is acquired immediately 
Antibodies not replaced 
Eg anti venom

Question 24

What is active immunity

Answer 24

Stimulating production of antibodies by individual’s own immune system
Contact with pathogen or antigen
Immunity takes time to develop but is long lasting

Question 25

What’s natural active immunity

Answer 25

Results from individual becoming infected with disease under normal circumstance

Question 26

What’s artificial active immunity

Answer 26

Forms the basis of vaccination

Involves inducing immune response without them suffering the symptoms of the disease

Question 27

What’s a vaccination

Answer 27

Introduction of appropriate disease antigens by injection or mouth
Intention is to stimulate immune response
Vaccine contains form of antigen but only small amount
Produces memory cells

Question 28

Features of successful vaccination programme

Answer 28

Economically available in sufficient quantities to immunise most of vulnerable population
Few side effects if any (unpleasant side effect may discourage others)
Means of producing, storing and transporting vaccine
Means of administrating vaccinepropely-trained staff
Possible for herd immunity

Question 29

What’s herd immunity

Answer 29

When a sufficiently large proportion of community is immunised
Difficult for pathogen to spread
Highly improbable that a susceptible individual will come into contact with pathogen

Question 30

What does vaccination not eliminate disease

Answer 30

• vaccination fails to induce in certain individuals
• individuals may develop disease before immunity levels high enough
• pathogen may mutate frequently so antibodies aren’t specific for th antigenic variability
• certain pathogens hide from body’s immune system ie in cells
• individuals have objections to vaccination ie religious,ethical,medical reasons

Question 31

Ethics of vaccines

Answer 31

Development of them involves animals?
Side effects balanced against harm of disease?
Should trials on humans be carried out?
Acceptable to trial new vaccine with no idea of side effects?

Question 32

Draw Human Immunodeficiency Virus

Answer 32

RNA 
Reverse transcriptase 
Matrix
Lipid envelope
Capsid
Attachment proteins

Question 33

How does HIV replicate

Answer 33

1-Enters bloodstream and circulates around body
2-Protein on hiv readily binds to CD4 protein on t helper cells
3-protein capsid fuses with cell surface membrane, rna and enzymes from hiv enter t helpercells
4-hiv reverse transcriptase converts virus’ rna into dna
5-dna of virus moves into t helper cells nucleus where it’s inserted into dna
6-hiv dna creates messenger rna using cells enzymes, mRNA contains instructions for making new viral components
7-mRNA passes out nucleus through nuclear pore, uses cells proteins synthesis mechanisms to make hiv particles
8-hiv particles break away with a bit of t helper cells cell surface membrane which form the lipid envelope

Question 34

How does hiv cause the symptoms of aids

Answer 34

• Causes aids by killing or interfering with normal functioning t helper cells
• aids sufferers have as low as 200 should be 1200 T cells
• no immune response so secondary diseases kill them

Question 35

What is Elisa test

Answer 35

Enzyme linked immunosorbant assay

Uses antibodies to detect presence and quantity of protein in a sample

Question 36

Process of Elisa test

Answer 36

1-apply sample to surface
2-wash surface several times to remove any unattached antigens
3-add antibody specific to antigen, allow to bind
4-wash to removes excesss antibody
5-add second antibody has enzymes attached
6-add colourless substrate of enzyme, enzyme acts on it changing colour
7-amount of antigen is relative to intensity of colour that develops

Question 37

Why are antibiotics ineffective against viral disease

Answer 37

• Bacterial cells have murein walls, tough material not easily stretched so will prevent further entry of water and antibiotics weaken the cell wall so burst
• viruses have no metabolic mechanisms or cell structures for antibiotics to disrupt so don’t work.