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Biology- Flynn > 2.4 Cell Recognition and the Immune System > Flashcards

2.4 Cell Recognition and the Immune System Flashcards

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1
Q

What is an infection?

A

The interaction between the pathogen and the bodies defence mechanisms

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2
Q

What is immunity?

A

The ability of organisms to resist infection by protecting against disease-causing microorganisms or their toxins that invade their bodies

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3
Q

What people are most susceptible to infection?

A

Old
Young
Weak

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4
Q

What are the two types of defence mechanisms?

A

Non-specific (immediate response, same for all pathogens)

Specific (slower response, specific to each pathogen)

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5
Q

Give examples of non specific defence.

A 
Physical barrier (skin)
Phagocytosis
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6
Q

Give examples of specific defence.

A 
Cell-mediated response (T lymphocytes)
Humoral response (B lymphocytes)
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7
Q

Why is it important that lymphocytes can detect foreign cells?

A

They would destroy the organisms own tissues otherwise

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8
Q

How do lymphocytes detect foreign cells?

A

Molecules (proteins) on the foreign cell surface

Proteins have specific tertiary 3D structure that can be identified

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9
Q

Name 4 foreign materials that a lymphocyte can detect.

A

Phagocytes
Non-self material
Toxins
Abnormal self cells (cancer)

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10
Q

Explain the complications of the efficiency of the immune system in organ transplants.

A

Non-self material is destroyed
Donor tissues have to be matched closely to self cells (usually family)
Immunosuppressant drugs given

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11
Q

Why is there a time lag between exposure to a pathogen and immune response?

A

All specific lymphocytes are present in the body in small numbers
It takes time for the the lymphocyte with a protein complementary to one of the proteins of the pathogen
The recognised lymphocyte is stimulated to divide to build in numbers to the extent it can destroy the pathogens
This is clonal selection

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12
Q

What is clonal selection?

A

Where a lymphocyte with a protein complementary to a protein on the pathogen is recognised and is stimulated to divide in order to have enough to fight the pathogen

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13
Q

Why is infection rare in a foetus?

A

Protected from the outside world by its mother (specifically the placenta)
Lymphocytes with receptors that fit the body’s self cells either die or are suppressed
The only remaining lymphocytes fit only foreign material so respond to it quickly

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14
Q

How are anti-self lymphocytes kept out of the blood?

A

Lymphocytes produced in bone marrow initially only encounter self-antigens
Lymphocytes that show immune response to self-antigens undergo cell death before they can differentiate into mature lymphocytes
These anti-self lymphocytes won’t make it as far as the blood

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15
Q

What is apoptosis?

A

Programmed cell death

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16
Q

What are the two types of white blood cell?

A

Phagocytes- ingest and destroy the pathogen

Lymphocytes- involved in immune response

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17
Q

What is phagocytosis?

A

Where large particles are engulfed by cells in the vesicles formed from the cell surface membrane

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18
Q

What causes phagocytes to move towards pathogens?

A

Chemical products of pathogens are detected by receptors in the cell surface of phagocytes
Dead, damaged, abnormal cells

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19
Q

What do you call the vesicles formed once a pathogen is engulfed by a phagocyte?

A

Phagosome

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20
Q

Describe all steps of phagocytosis.

A

Phagocytes is attracted to pathogen by its chemical products, moving toward the pathogen along a concentration gradient.
Receptors on the phagocyte attach to chemicals on the surface of the pathogen.
Lysosomes inside the phagocyte move toward the phagosome formed by engulfing the pathogen.
Lysosomes release their lysozymes into the phagosome, where they hydrolyse the pathogen.
The hydrolysis products of the bacterium are absorbed by the phagocyte.

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21
Q

How are pathogens actually killed in phagocytosis?

A

Lysosomes release their lysozymes which hydrolyse the cell wall of the pathogen

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22
Q

What is an antigen?

A

Any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune response

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23
Q

Where are antigens usually found?

A

As proteins that are part of the cell-surface membranes or cell walls of invading cells

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24
Q

What immune response does an antigen trigger?

A

The production of an antibody

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25
Q

How are lymphocytes produced?

A

By stem cells in the bone marrow

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26
Q

What is humoral immunity?

A

Immunity involving antibodies that are present in the body fluids
(B cells)

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27
Q

Where are T cells produced?

A

Thymus gland

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28
Q

What is cell-mediated immunity?

A

Immunity involving body cells

T cells

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29
Q

How do T lymphocytes distinguishes between invader cells and normal cells?

A

Phagocytes that have engulfed and hydrolysed a pathogen have some of the pathogen’s antigens on their own cell surface membrane
Body cells invaded by a virus have some of the viral antigens in their own cell surface membrane
Transplanted cells have different antigens on their cell surface membrane
Cancer cells and different from normal body cells and have antigens on their cell surface membrane

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30
Q

What is an antigen presenting cell?

A

A cell that displays foreign antigens on their surface

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31
Q

Why are there so many types of T cell?

A

The receptors on each T cell respond to a single antigen

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32
Q

What are the stages undertaken by a T lymphocyte in response to infection by a pathogen?

A

Pathogens invade body cells or are taken in by phagocytosis.
The phagocyte places antigens from the pathogen on its cell surface membrane.
Receptors on a specific helper T cell fit exactly onto these antigens.
This attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells.

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33
Q

What 4 things can the cloned T cells do?

A

Develop into memory cells
Stimulate phagocytosis
Stimulate B cells to divide and secrete their antibody
Activate cytotoxic T cells

34
Q

How to cytotoxic T cells kill infected cells?

A

Produce a protein called perforin
This makes holes in the cell surface membrane
The holes make the membrane freely permeable to all substances
This kills it

35
Q

Why are T cells most effective against viruses?

A

As they replicate inside cells

36
Q

Why is humoral immunity associated with antibodies?

A

Involves body fluids and antibodies are soluble in blood and tissue fluid of the body

37
Q

By what process do antigens enter a B cell?

A

Endocytosis

38
Q

How is a clone of identical B cells produced?

A

Helper T cells bind to the processed antigens and stimulate the B cell they’re attached to do divide by MITOSIS

39
Q

What are monoclonal antibodies?

A

The antibodies produced by a cloned lymphocyte

40
Q

What two types of cell can a lymphocyte clone develop into?

A

Plasma cells

Memory cells

41
Q

What do plasma cells do?

A

Secrete antibodies into blood plasma
Survive for a few days
Destroy the antigen
Primary immune response (immediate action)

42
Q

What do memory cells do?

A

Secondary immune response
Very long life
Divide rapid when they encounter an antigen again and develop into more plasma and memory cells

43
Q

Explain the process by which B cells work.

A

Surface antigens of an invading pathogen are taken up by a B cell.
B cell processes the antigens and presents then on its surface
Helper T cells attach to the processes antigens on the B cell (activates it).
The B cell is activated to divide by mitosis to give a clone of plasma cells.
Cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogens surface.
The antibody attaches to antigens on the pathogen and destroys them.

Some develop into memory cells.

44
Q

Define antibody.

A

Proteins with specific binding sites synthesised by B cells

45
Q

What are antibodies made up of?

A

4 polypeptide chains
A pair of longer “heavy chains”
A pair of shorter “light chains”

46
Q

What is formed when an antibody binds to an antigen?

A

Antigen-antibody complex

47
Q

What is the variable region?

A

The binding site of an antibody that is different on different antibodies

48
Q

What is the constant region?

A

The rest of the antibody (the non binding site bit)

49
Q

What are the two ways an antibody assists in the destruction of antigens?

A

Cause agglutination of the bacterial cells (clumps of bacterial cells are formed, makes it easier for the phagocytes to locate them as they are less spread-out within the body)
Serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached

50
Q

In what ways are monoclonal antibodies useful practically?

A

Attachment of therapeutic drugs to a certain antibody
Medical diagnosis
Pregnancy testing

51
Q

How are monoclonal antibodies used to treat cancer?

A

Monoclonal antibodies that are specific to antigens on cancer cells are produced
Their antibodies are given to a patient and attach themselves to the receptors on their cancer cells
They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth

52
Q

What is the advantage of using monoclonal antibodies in cancer treatment?

A

The antibodies are not toxic and are highly specific so have fewer side effects

53
Q

What is indirect monoclonal antibody therapy?

A

Involves attaching a radioactive or cytotoxic drug to the monoclonal antibody.
When the antibody attaches to the cancer cell it kills it

54
Q

What’s the advantage of indirect monoclonal antibody therapy?

A

Smaller doses are cheaper and reduce side effects

55
Q

What are the ethical issues around monoclonal antibodies?

A

Production involves using mice and giving them cancer
People have died when they’re used to treat multiple sclerosis (need informed consent where people know the risks)
Volunteers in drug trials have almost died

56
Q

Define immunity.

A

The ability of an organism to resist infection

57
Q

What is passive immunity?

A

The introduction of antibodies into individuals from an outside source
Immunity acquired immediately
There is no lasting immunity as so memory cells are formed as the individual is not producing the antibodies themselves

58
Q

What is active immunity?

A

Stimulating the production of antibodies by the individuals own immune system
Immunity takes time to develop
Natural- individual becomes infected under normal circumstances
Artificial- essentially vaccination

59
Q

What is vaccination?

A

The introduction of the appropriate disease antigens into the body (by injection or mouth)
To stimulate an immune response against a particular disease

60
Q

Why are vaccinations useful?

A

Produces memory cells

These remain in the blood and allow for a more immediate response to a future infection of the pathogen

61
Q

What is a successful vaccination programme dependant on?

A

Suitable vaccine must be economically available in sufficient quantities to immunise most of the vulnerable population (to produce herd immunity)
Few side effects
Means of producing, storing and transporting the vaccine
Means to administer the vaccine protect at appropriate time

62
Q

When does herd immunity arise?

A

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

63
Q

Why is herd immunity important?

A

It’s never possible to vaccinate everyone

Eg babies/ill people as their immune systems are weak

64
Q

Why may vaccination not eliminate a disease?

A

People have defective immune systems that make the vaccine fail
Vaccinated individuals may reinfect others
Pathogen may mutate (antigenic variability)
A pathogen may have too many variants to vaccinate against them all
Some pathogens ‘hide’ themselves (inside cells/out of reach)
People may object to being vaccinated for medical, ethical or religious reasons

65
Q

What are some ethical issues surround vaccination?

A 
Trials on animals
Side effects
Trails on humans
Should they be compulsory 
Expense (vaccination vs treatment)
66
Q

What does HIV stand for?

A

Human immunodeficiency virus

67
Q

What is AIDS?

A

Acquired immune deficiency syndrome

Caused by HIV

68
Q

What is the structure of HIV?

A

Lipid envelope outside with embedded attachment proteins
Inside the envision is a protein layer called the capsid
The capsid contains two single strands of RNA and some enzymes (one is reverse transcriptase)

69
Q

What is reverse transcriptase?

A

The enzyme that catalysed the production of DNA from RNA

70
Q

What makes HIV a retrovirus?

A

It has reverse transcriptase and so can make DNA from RNA

71
Q

Why can’t HIV replicate itself?

A

Because it’s a virus

72
Q

How does HIV replicate?

A

Uses its genetic material to instruct the host cells biochemical mechanisms to produce to components required to make new HIV

73
Q

Describe the process of HIV replication.

A

HIV enters the bloodstream
A protein on the HIV binds to a protein called CD4 (most frequently on T cells)
The protein capsid fuses with the cell surface membrane so the RNA and enzymes of HIV enter the helper T cell
HIV reverse transcriptase converts the viruses RNA into DNA
Newly made DNA is moved into the helper T cells nucleus where it is inserted into the cells DNA
HIV DNA in the nucleus creates mRNA using the cells enzymes, this contains the instruction for making new viral proteins and the RNA to go into the new HIV
mRNA passes out of the nucleus through a nuclear pore and used the cell’s protein synthesis mechanisms to make HIV particles
HIV particles break away from the helper T cell with a piece of its cell surface membrane surrounded them which forms the lipid envolope

74
Q

Simply describe the process of HIV replication.

A

Enters bloodstream
HIV protein binds to helper T cells
HIV capsid fuses with cell membrane to release its RNA and enzymes
Reverse transcriptase converts RNA to DNA
HIV DNA is inserted into the nucleus and into the cells DNA
This HIV DNA creates mRNA to make new viral proteins
mRNA leaves nucleus and makes HIV particles
HIV particles break away from helper T cell, forming their lipid envelope by taking a piece of its cell surface membrane

75
Q

How does HIV cause AIDS?

A

By killing of interfering with the normal functioning of helper T cells
Less T cells means B cells aren’t stimulated to produce antibodies etc
Left susceptible to infections and cancers

76
Q

What does ELISA stand for?

A

Enzyme linked immunosorbent assay

77
Q

What does the ELISA test do?

A

Uses antibodies to detect the presence of a protein in a sample as well as the quantity

78
Q

What are the positives of the ELISA test?

A

Very sensitive so can detect very small amount of a molecule

Used for drug and allergen tests

79
Q

How is an ELISA test done?

A

Apply sample to a surface that the antigens will attach to
Wash the surface to remove unattached antigens
Add the antibody specific to the antigen we’re trying to detect and leave them to bind together
Wash the surface to remove excess antibody
Add a second antibody that binds with the first antibody (this has an enzyme attached to it)
Add the colourless substrate of the enzyme attached to the second antibody, the enzyme acts on the substrate to produce a coloured product
Amount of antigen present is relative to the intensity of the colour that develops

80
Q

Why are antibiotics ineffective against viral diseases?

A

Antibiotics can’t teach viruses as they’re inside the organisms own cells to reproduce
Viruses have a protein coat and not a murein cell wall and so don’t have sites that antibiotics can work

Biology- Flynn (11 decks)

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