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Cell recognition and the immune system Flashcards

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1
Q

YType of defence mechanisms

A

Non specific = immediate (physical barrier and phagocytosis)
Specific = slow and specific to all pathogens (cell-mediated responses and humoral response)

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2
Q

What do cell-mediated and humoral responses involve

A

Cell-mediated = T lymphocytes
Humoral responses = B lymphocytes

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3
Q

What must lymphocytes be able to do to defend the body?

A

Distinguish self and non-self molecules

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4
Q

How do lymphocytes distinguish between self and non-self material

A

Proteins on surface
Have specific tertiary structure so can be distinguished between cells

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5
Q

What do the proteins on the surface help lymphocytes identify

A

Pathogens
Non-self material
Toxins
Abnormal bods cells

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6
Q

What is phagocytosis

A

When large particles are engulfed in the vesicles of the cell-surface membrane

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7
Q

Where do phagocytes travel

A

In the blood and tissues

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8
Q

Stages of phagocytosis

A

1) Pathogens toxins attract phagocyte
2) Lysosomes fuse with phagosome
3) Lysozymes hydrolyse ingested bacteria

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9
Q

What is an antigen

A

Substance that is recognised as non-self and stimulates your immune system to produce antibodies

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10
Q

How are lymphocytes produced

A

By stem cells in the bone marrow

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11
Q

What are the two types of lymphocytes

A

B lymphocytes and T lymphocytes

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12
Q

What are B lymphocytes

A

In bone marrow
Humoral immunity
Involve antibodies
Present in body fluids

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13
Q

What are T lymphocytes

A

In thymus gland
Cell-mediated immunity
Involve body cells

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14
Q

What do lymphocytes respond to

A

Non-self material from different species and from other individuals (because they are genetically different)

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15
Q

How can T lymphocytes distinguish invader cells from normal ones?

A

Once hydrolysed, they keep some of pathogens antigens on their cell-surface membrane

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16
Q

What do T lymphocytes response to

A

Antigens presented on body cell

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17
Q

Response of T lymphocytes to infection by pathogen stages

A

1) Pathogens taken in by Phagocytes
2) Receptors on T cell fix onto antigens
4) T cell undergoes mitosis
5) Cloned cells turn into memory cells which stimulates phagocytosis, so B cells divide, activating cytotoxic t cells

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18
Q

What are cytotoxic t cells

A

Kill abnormal cells and body cells infected by pathogens

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19
Q

What do cytotoxic t cells do

A

Produce perforin that makes holes in cell-surface membrane

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20
Q

Why do cytotoxic cells make holes in cell-surface membrane

A

Mean cell membrane becomes freely permeable to all substances, so cell dies

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21
Q

What’s it called when an antigen enters a C cell

A

Endocytosis

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22
Q

What does humoral immunity produce

A

Antigen specific antibodies

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23
Q

What plasma cells do and what defence they are

A

Secrete antibodies
Produce antibodies that destroy antigens
Immediate defence

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24
Q

What do memory cells do, how do they help defend the body from pathogens and what response are they

A

Secondary immune response
When encounter same antigen, divide rapidly and develop into plasma and memory cells
Plasma cells produce antibodies
Memory cells remember killing antigen process
Long-term immunity

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25
Q

How B cells work

A

1) B cells with complementary receptors divide by mitosis
2) Some B cells become plasma cells producing antibodies
3) Some B cells turn into memory cells

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26
Q

Antibodies

A

Proteins with specific binding sites synthesised by B cells

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27
Q

What are antibodies made up of

A

4 polypeptide chains
Heavy chains
Light chains

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28
Q

How is an antigen-antibody complex formed

A

Antibody has specific binding site that fits onto specific antigen

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29
Q

What is the binding site on antibodies called

A

Variable region

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30
Q

What do variable regions contain that make them different on different antibodies

A

They consist of a sequence of amino acids that form a specific 3D shape that binds directly to a specific antigen

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31
Q

What is the bottom part of an antibody knows as

A

Constant region

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32
Q

What are the two ways antibodies assist in destroying antibodies

A

Cause agglutination in bacterial cells
Stimulate phagocytes to engulf bacterial cells

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33
Q

What is agglutination

A

Clumps of bacteria form so phagocytes can locate them easier as they are less spread out in the body

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34
Q

Monoclonal antibodies definition

A

artificially produced antibodies produced from a single B cell clone

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35
Q

What does direct monoclonal antibody therapy do

A

Stop growth of cancer cells

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36
Q

How does direct monoclonal antibody therapy work

A

MA are specific to antigens on cancer cells
Antibodies given to patient and attach to receptors on cancer cells on their surface
Block chemical signals that cause mitosis of cancer cells

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37
Q

Advantage of direct monoclonal

A

Not toxic
Highly specific
Few side effects than other forms of therapy

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38
Q

What does indirect monoclonal antibody therapy do

A

Kill cancer cells

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39
Q

How does indirect monoclonal antibody therapy work

A

Radioactive or cytotoxic drug attaches with monoclonal antibody
Antibody attaches to cancer cells and kills them

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40
Q

Advantages of indirect monoclonal antibody therapy

A

Can be used in smaller doses
Targeted on specific sites
Cheaper in small doses
Reduces side effects other drugs might have

41
Q

Monoclonal antibodies also used in

A

Medical diagnosis -> ELISA tests
Pregnancy testing -> placenta produces hormone (human chorionic gonaclatrophin), monoclonal antibodies attach and bind to coloured particles. HCG-antibody-colour complex moves along strip, trapped by different antibody creating colour on pregnancy test

42
Q

Ethical issues of monoclonal antibodies

A

Infuse mice with cancer and extract tumour cells and antibodies
Been some deaths in treatment
6 patients suffered organ failures in durg trial

43
Q

Suggest two further investigations that should be done before this ADC is tested on human breast cancer patients [2 marks]

A

Test on healthy humans
Test on other mammals to check for side effects
Investigate difference concentrations of ADC to find safe dosage

44
Q

Production of monoclonal antibodies

A

1) Mouse exposed to non-self material
2) B cells produce antibodies
3) B cells extracted from spleen
4) B cells mix with cancer cells
5) Detergent added to break down cell-surface membranes
6) Cells fuse together forming hybridoma cells
7) Hybridoma cells separated under microscope
8) Each cell is cultured to form clone
9) Clones tested so that they are producing correct antibody
10) Antibody grown and antibodies extracted from from growth medium

45
Q

Passive Immunity

A

Introduction of antibodies into individuals from outside source
Antibodies aren’t being produced by individuals so cannot be replaced by them

46
Q

Active immunity

A

Stimulating production of antibodies by individual’s own immune system
Direct contact with pathogen is necessary
Long-lasting

47
Q

Natural active immunity

A

Individual infected with disease under normal conditions
Body produces its own antibodies

48
Q

Artificial active immunity

A

Vaccination
Inducing immune response
(Without suffering symptoms)

49
Q

What do vaccinations force the body to do

A

Stimulte immune response

50
Q

What happens to the injected vaccine

A

Remains in blood

51
Q

What do vaccinations allow

A

Greater, more immediate response to future infections
Resulting in rapid production of antibodies

52
Q

What are some things vaccinations success depends on

A

Economically available
Few side effects
Producing storing transporting vaccine must be available
Appropriate time of training staff
Herd immunity must be possible

53
Q

What is herd immunity

A

When a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to pass from individual to individual

54
Q

Why is herd immunity important

A

Never possible to vaccinate everyones (children, ill people)

55
Q

Primary response

A

Multi-step pathway from antigen presenting cells to create antibodies

56
Q

Secondary response

A

Stimulates B cells to cause secretion of more antibodies more rapidly

57
Q

Cell-mediated response

A

Product Cytotoxic T cells
Only bind to antigens presenting host cell and destroy that cell

58
Q

Why might a vaccination not eliminate a disease

A

Fails to induce immunity in certain individuals
Develop disease immediately after vaccination
Antigenic variability = may mutate its antigens to change suddenly, so vaccines are ineffective
Too many varieties of the pathogen its impossible to develop vaccine for them all
Some pathogens hide from body’s immune system
Objections to vaccination for religious, ethical or medical reasons

59
Q

Ethical issues with vaccines

A

Uses animals
Side effects -> can be long term
Taking risks in interest of public
Who should vaccines be tested on
Is it acceptable to trial a new vaccine with unknown health risks
Expensive

60
Q

How does HIV replicate

A

1) Enters bloodstream circulates body
2) Protein on HIV binds to helper T cells
3) Protein capsid fuses with cell-surface membrane
4) RNA and enzymes of HIV enter T cell
5) HIV reverse transcriptase converts virus’s RNA into DNA
6) DNA inserted into helper T cell’s nucleus
7) HIV DNA in nucleus created mRNA
8) mRNA passes out nucleus through nuclear pore and uses cell’s protein synthesis mechanisms to maKe HIV particles
9) HIV particles break away from helper T cell with piece of its cell-surface membrane forming lipid envelope

61
Q

What is an ELISA test used for

A

Uses antibodies to detect presence of a protein

62
Q

How do bacterias cell walls not burst

A

walls made out of murein
Cell wall resists expansion

63
Q

Why are antibiotics ineffective in Viruses

A

Viruses rely on host cells to carry out metabolic activities
Ineffective because there are no metabolic mechanisms
AND they have protein coats so do not have sites where antibiotics can work

64
Q

Outside layer of HIV

A

Lipid envelope

65
Q

Pegs going into HIV

A

Attachment proteins

66
Q

Rectangle envelope surrounding subsystems in HIV

A

Capsid

67
Q

What does capsid contain HIV

A

RNA and enzymes

68
Q

What’s an important enzyme contained in the capsid in HIV and what does it do

A

Reverse transcriptase
Catalyses production of RNA to DNA

69
Q

Name of viruses that can transfer RNA to DNA

A

Retroviruses

70
Q

Second inner layer of HIV

A

Matrix

71
Q

What are red blod cells official name

A

Erythrocytes

72
Q

What is white blod cells official name

A

Leucocytes

73
Q

What are the two types of white blod cells

A

Phagocytes and lymphocytes

74
Q

What do phagocytes do

A

Phagocytosis
Engulf pathogens, hydrolysing enzymes to digest pathogen
Present antigens on cell surface membrane

75
Q

What do lymphocytes and phagocytes have to distinguish them

A

Lymphocytes have much larger nucleus

76
Q

What are the two types of lymphocytes

A

T and B cells

77
Q

What do t cells do

A

Identify non-self

78
Q

What are the three types of T cells

A

T helper
T cytotoxic
T memory

79
Q

What are B cells used for

A

Monoclonal antibody production

80
Q

How does the ELISA test work

A

1) Apply sample to surface of slide for antigens to attach to
2) Wash surface to remove unattached antigens
3) Add antibody specific to antigen to detect and leave two to bind (apply patients blood with HIV)
4) Wash surface to remove excess antibody (wash blood off)
5) Add second antibody to bind with first antibody
6) Add colourless substrate of enzyme, enzyme attach to substrate and changes colour
7) Amount of antigen present shows different colour intensity

81
Q

Why are antibiotics ineffective against viral diseases

A

1) Viruses rely on host cells to carry out metabolic activities (they dont have metabolic pathway), no cell structure or mechanism for antibiotics to disrupt
2) Protein coat does not have sites where antibiotics work so antibiotics can’t reach them

82
Q

How do antibiotics work

A

In bacterial cells water constantly enters by osmsis
Murein wall surrounding bacterial cell is tough, as water enters cell expands and wall resists.
Antibitics inhibit enzymes required for synthesising peptide cross-linkages in cell walls of bacteria
Weakening the walls, making them unable to withstand pressure and burst

83
Q

How does HIV cause AIDS symptoms

A

HIV attacks T helper cells
Immune system can’t stimulate B cells to produce antibodies and cytotoxic T cells
Also affecting memory cells
Body can’t produce effective response to other infections and cancers

84
Q

How does your body not kill it’s self material

A

1) T cells mature in thymus
2) When the T cells are maturing, immature lymphocytes will only encounter self antigens
3) If they react to self antigens (which they are not meant to), they will undergo apoptosis (Self death of cell)
4) This measn that we dont get any self reactive lymphocytes in the bloodstream

85
Q

What is apoptosis

A

Programmed cell death

86
Q

Describe phagocytosis

A

1) Chemicals from the non-self material act as attractants for the phagocytes
2) Phagocytes move towards the attractants
3) Phagocytes will detect the pathogens using their cell surface receptors
4) They engulf the pathogen inside a phagosome
5) The lysosome releases enzymes/lysozymes into the phagosome
6) This breaks down the pathogen into debris which can be absorbed into the cytoplasm
7) The cycle repeats with another pathogen

87
Q

Difference between phagocytes and lymphocytes

A

Phagocytes = non specific
Lymphocytes = specific

88
Q

Two types of lymphocytes

A

T cells and B cells

89
Q

Types of t cells and b cells

A

T cells = memory T cell, helper cells (th), cytotoxic t cells (Tc)
B cells = plasma cells, memory B cell

90
Q

How are T helper cells activated

A

1) Phagocyte presents non self material (pathogen) on its cell surface membrane
2) T helper cells recognise the antigen and activate the specific response

91
Q

What do cytotoxic t cells do

A

Stop the infected cells replicating through perforin (making holes in virus)

92
Q

What do plasma cells from B cells do

A

Activated when virus complementary attaches to presented antigen receptor on B cell
In order to produce more B cells by mitosis with specific antigens present that are also complementary to the pathogens antigen, so there are more B cells to kill the pathogens

93
Q

What are plasma cells

A

Name we give to B cells that produce antibodies

94
Q

What type of molecules do antigens detect are non self

A

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

95
Q

What is an antigen

A

The effect of antigen variability on disease and disease prevention

96
Q

What is phagocytosis definition

A

Destruction of ingested pathogens by lysozymes

97
Q

What is an antigen presenting cell

A

ANtigen-presenting cell is one of the host’s cels that has been invaded by a pathogen and is displaying the antigen on its cell surface membrane
T cells only bind to antigen if it’s present on an antigen-presenting cell

98
Q

What does an antigen presenting cell do

A

Present antigens from toxins, foreign cells and ingested pathogens
Help recruit other cells for specific immune response
Once surface receptor of T cell binds to specific complementary antigen on antigen presenting cell is becomes sensitised and starts dividing to produce a clone of cells

99
Q

Example of antigen-presenting cells

A

Macrophages and dendritic cells

Biology (57 decks)

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