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Biology > Pack 6 - Cell Recognition and the Immune System > Flashcards

Pack 6 - Cell Recognition and the Immune System Flashcards

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1
Q

What is Immunity?

A

Immunity is the ability of a multicellular organism to resist infection or disease by micro-organism/pathogens.

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2
Q

What type of molecules are antigens usually composed of and why this type of molecule?

A

Proteins - due to their varied and and specific tertiary 3D structure.

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3
Q

Why are antigens crucial to the immune system?

A

They allow lymphocytes to identify cells as self or non-self.

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4
Q

Give four different examples of cell/molecule that can be identified, due to antigens, by the lymphocytes as non-self.

A
  • Pathogen
  • Cells/material from other organism (or outside the body in general)
  • toxins
  • abnormal body cells e.g. cancer cells
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5
Q

In terms of immune response describe briefly how an organ transplant could cause an issue. How could this response be minimised?

A

• The immune system would recognise the tissue as non-self and attempt destroy the tissue.

  • Immunosuppressant drugs
  • Selecting donors that are closely related.
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6
Q

How does the immune system initally recognise a foreign antigen?

A

10 million lymphocytes each specific to a different antigen already exist. There are therefore initially very few lymphocytes specific to one specific antigen.

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7
Q

Describe how lymphocytes only recognise non-self antigens? (Formed in the foetus and bone marrow of adults)

A
  • In the foetus, lymphocytes that are specific to body cells will collide with only body cells. These lymphocytes die or are suppressed. Therefore only the remaining lympohctyes that will be specific to non self antigens survive.
  • Lymphocytes produced in the bone marrow initially only encounter body cells.
  • Lymphocytes that show an immune response to these self antigens undergo programmed death before they can differentiate.
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8
Q

What is the difference between non specific and specific defence mechanisms?

A
  • Non specific - responds in the same way to all pathogens (phagocytosis/barriers)
  • Specific - specific to each pathogen (lymphocytes)
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9
Q

What is the bodies first defence against pathogens?

A

• Physical barriers - e.g. skin

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10
Q

What is the initial and immediate response to defend against any pathogen that enter the body?

A

Phagocytosis

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11
Q

Where are phagocytes found?

A

In the blood but some can move out of blood vessels.

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12
Q

Describe the process of phagocytosis in 5 steps.

A
  • Phagocyte is attracted to the pathogen by chemicals released by the pathogen, moving towards the pathogen along a concentration gradient.
  • The phagocyte has several receptors on its cell surface that attach to chemicals on the surface of the pathogen.
  • A phagosome (vesicle) forms around the pathogen, engulfing it.
  • Lysosomes fuse with the phagosome releasing digestive (lysozyme) enzymes into the phagocyte.
  • The products of the hydrolysis of the pathogen are absorbed or related by the phagocyte.
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13
Q

What is an antigen?

A

Any part of an organism or substance that is recognised as non-self by the organism.

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14
Q

What are the two types of lymphocytes? where are they produced? and where do they mature?

A
  • B - lymphocytes are produced by stem cells in the bone marrow and mature in the bone marrow.
  • T - lymphocytes are produced by stem cells in the bone marrow and mature in the thymus gland.
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15
Q

What type of immunity are B - lymphocytes associated with?

A

Humoral immunity (body fluids) - involving antibodies in the blood plasma for example.

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16
Q

What type of immunity are T - lymphocytes associated with?

A

Cell-mediated immunity - involving body cells.

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17
Q

What type of cells do T - Lymphocytes respond to? Give four examples.

A

Body cells. Antigen presenting cells.

  • Phagocytes (presents engulfed antigens)
  • Body cells invaded by a virus
  • Transplanted cells
  • Cancer cells

All these cells are BODY CELLS but have NON-SELF antigens.

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18
Q

What is a body cell that displays foreign antigens called?

A

An antigen-presenting cell.

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19
Q

Name three types of T Lymphocytes

A
  • T Helper cells
  • Cytotoxic T Cells
  • T memory cells
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20
Q

Describe in 4 stages the response of T Lymphocytes to infection by a pathogen.

A
  1. Pathogen invade body cells or are taken up by phagocytosis.
  2. The phagocyte places antigens from the pathogen on its cell surface membrane (or infected body cells present the pathogens antigen)
  3. Receptors on a specific T Helper cell for exactly into these antigens.
  4. This attachment activates T helper cells to divide by mitosis and form a clone of genetically identical cells.
5. Some clones: 
    • develop into Memory cells
    • activate Cytotoxic cells 
    • stimulate B cells to divide
    • stimulate phagocytes
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21
Q

Describe the roles of cloned T Lymphocytes.

A
  • Develop into memory cells
  • stimulate phagocytes
  • Stimulate B cells to divide
  • Activate cytotoxic T cells
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22
Q

What is the role of cytotoxic T cells and how do they carry out this role?

A

To kill abnormal or infected body cells.

They produce perforin that makes holes in the cell surface membrane. Therefore the cells dies as the membrane is fully permeable.

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23
Q

What do B Lymphocytes antibodies respond to?

A

Antigens in the body fluids. E.g. on a pathogen.

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24
Q

Name the two types of B Lymphocytes

A
  • B memory cells

* Plasma cells

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25
Q

What is the process called by which a B Lymphocyte takes in a foreign antigen? What does it do with this antigen?

A

Endocytosis

Presents it on its cell surface

26
Q

What is clonal selection?

A

The stimulation, by T helper cells binding to processed antigens, of B cells to divide by mitosis.

27
Q

Why will many different B cell clones be produced in response to one pathogen.

A

Pathogens contain many different antigens so many different B cell clones are produced that produce different antibodies.

28
Q

What is the role of plasma cells.

A

Produce antibodies

29
Q

What is the name for the productions of antibodies and memory cells in response to a pathogen?

A

Primary immune response

30
Q

What are memory cells responsible for?

A

Secondary immune response.

31
Q

If a second infection occurs describe how the immune system would respond.

A

Lots of memory cells in the blood and tissue fluid.

Divide rapidly into plasma cells and more memory cells.

Plasma cells produce antibodies at an increased rate to in the primary response.

32
Q

Describe the role of B cells in humoral immunity. 7 steps

A
  1. Surface antigens of an invading pathogen are taking up by B cells.
  2. B cell processes the antigens and presents them on their surface.
  3. Helper T cells attach to the processed antigens on the B cell, thereby activating it.
  4. B cell divides by mitosis to create a clone of plasma cells.
  5. Some B cells develop into memory cells. For the secondary immune response.
  6. Plasma cells produce and secrete antibodies complementary to the antigens on the pathogens surface.
  7. Antibodies attach to antigens on the pathogen and destroy it.
33
Q

Describe the structure of an antibody.

A
  • Four polypeptide chains.
  • 2 heavy chains, 2 light chains.\ //
34
Q

What differs between different antibodies?

A

The antigen binding site which fits precisely into different antigens.

35
Q

What is the name for an antibody that is bound to an antigen at the antigen binding site?

A

Antigen-antigen complex.

36
Q

What does the constant region bind to?

A

Receptors on cells. For example B cells.

37
Q

How do antibodies lead to the destruction of bacteria?

A
  • agglutination

* serve as markers that stimulate phagocytosis

38
Q

Describe the process of agglutination.

A
  • Each of the TWO antigen binding sites of an antibody bind to the antigens on different pathogens.
  • This clumps together groups of the pathogen.
  • Phagocytes receptors bind to the receptor binding site on the antibodies and therefore can easily engulf the pathogens.
39
Q

What is a monoclonal antibody?

A

Antibodies all with exactly the same tertiary structure. E.g. they all fit the same antigen.

40
Q

Name the two ways in which monoclonal antibodies can be used to treat cancers.

A
  • Direct monoclonal antibody therapy

* Indirect monoclonal antibody therapy.

41
Q

Describe how direct monoclonal antibody therapy can be used to treat cancers.

A
  • Monoclonal antibodies, specific to antigens on cancer cells, are produced.
  • These antibodies are given to the patient and attach themselves to the receptors on their cancer cells.
  • This blocks the chemical signals that stimulate their uncontrolled growth.
42
Q

Describe how indirect monoclonal antibody therapy can be used to treat cancers.

A
  • A radioactive or cytotoxic drug is attached to the monoclonal antibody that is specific to cancer cells.
  • Antibody attaches to the cancer cell and delivers the drug directly to the cancer cells, killing them.
  • This is therefore very targeted so smaller doses can be given, reducing side effects.
43
Q

Other than medical treatment give two other uses of monoclonal antibodies.

A
  • Medical diagnosis.

* pregnancy tests

44
Q

Give three ethical issues with using monoclonal antibodies.

A
  • Their productions involves inducing cancer in mice.
  • There have been some deaths associated with using monoclonal antibodies.
  • Testing their safety can be dangerous.
45
Q

What is the difference between:

  • Natural active immunity
  • Artificial active immunity
A
  • Natural active immunity results from an individual becoming infected by a disease naturally. The bodies response usually produces long term Immunity.
  • Artificial active immunity involves a vaccination.
46
Q

What is the difference between active and passive immunity?

A
  • Passive immunity is achieved by the introduction of antibodies into an individual from an outside source. This is not long lasting as the individual is not producing antibodies or memory cells.
  • Active immunity is produced by stimulating the production of antibodies by the individuals plasma cells. Takes time to develop and is usually long lasting. Memory cells are produces.
47
Q

Give two examples of passive immunity.

A
  • anti venom

* antibodies passed to a baby from a mothers placenta.

48
Q

Define vaccination.

A

The introduction of disease antigens into the body to stimulate an immune response.

49
Q

Describe how a vaccination produces long term immunity.

A

The initial response produces memory cells. Therefore after a second infection the response is greater and more immediate.

50
Q

Give 5 features of a successful vaccination programme.

A
  • must be economically available to immunise the majority of the population.
  • few side effects - is any
  • must be means of producing storing and transporting the vaccine.
  • must be means of administering the vaccine properly and at the right time.
  • must be possible to immunise the vast majority of the population.
51
Q

What is herd immunity?

A

When a large proportion of the population has immunity so that it makes it very difficult for the pathogen to spread within the population.

52
Q

Why is herd immunity important to consider during a vaccination programme?

A

It is not possible to vaccinate every individual. For example babies and young children or those with compromised immune systems. Herd immunity means those that cannot be vaccinated are protected and are unlikely to get the disease.

53
Q

Why might a vaccine not eliminate a disease? (6 reasons)

A
  • May fail to induce immunity in certain individuals.
  • Individuals may develop the disease immediately after vaccination but before immunity levels are high enough to prevent it. Therefore they may harbour the disease.
  • Pathogen may mutate frequently (antigen variability).
  • There may be many varieties of a particular pathogen - impossible to develop a vaccine effective against them all.
  • Pathogen ‘hide’ from the immune system. e.g. inside cells.
  • Individual objections e.g. religious or ethical
54
Q

Give 6 potential ethical issues with vaccines.

A
  • Often use animal testing.
  • Can have side effects that may sometimes cause long term harm.
  • On whom should they be tested.
  • Should they be compulsory to achieve herd immunity.
  • Could be expensive for diseased that have nearly been eradicated - money could treat other diseases.
  • Individual health risks balanced against population health.
55
Q

Describe the structure of HIV (6 components).

A
  • RNA and Enzymes (such as reverse transcriptase).
  • Surrounded by a capsid (protein).
  • Surrounded by matrix (protein).
  • Surrounded by a lipid envelope.
  • Embedded with attachment proteins.
56
Q

Describe in 8 steps the replication of HIV.

A
  • HIV enters blood stream.
  • A protein on HIV binds to CD4 found on T-Helper cells.
  • Capsid fuses with the cell surface membrane. RNA and enzymes released into the T cell.
  • HIV reverse transcriptase converts the virus’s RNA into DNA
  • This DNA is moved to the nucleus and is inserted into the cells DNA.
  • This DNA creates mRNA.
  • This mRNA eases out the nucleus to ribosomes and HIV components are synthesised.
  • HIV particles break away and lipid envelope forms from the T cells membrane.
57
Q

How does HIV cause AIDS?

A

It interferes with or kills T Helper cells which are important for immunity to other pathogens.

58
Q

Describe the ELISA test in 7, testing for the presence of an antigen.

A
  • Attach the antigen to a surface.
  • Wash the surface to remove unattached antigens.
  • Add the antibody specific to the antigen.
  • Wash to remove unattached antibodies.
  • Add a second antibody attached to an enzyme that will bind to the first antibody.
  • Add the colourless substrate of the enzyme.
  • The amount of antigen present is relative to the intensity of colour that develops.
59
Q

How does penicillin kill bacterial cells?

A
  • It inhibits enzymes that synthesis bacterial cell walls.

* Therefore water enters by osmosis and the cells burst.

60
Q

What is a bacterial cell wall made of?

A

Murien

Biology (18 decks)

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