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A Level Biology > Topic 6.3 The response to infection > Flashcards

Topic 6.3 The response to infection Flashcards

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1
Q

What is an antigen?

A
  • cell surface membrane that can stimulate an immune response
  • usually glycoprotein or lipid/ polysacchairde
  • immune system recognises ‘self’ or ‘non-self’ which enables identification of cells from other organisms of the same species, pathogens, toxins + abnormal body cells
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2
Q

Outline the process of inflammation

A
  1. Damaged cells release histamines, causing vasodilation
  2. Blood flow and permeability of vessels increases
  3. White blood cells and plasma into the infected tissue
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3
Q

Name the 2 types of WBC involved in phagocytosis

A
  • neutrophils

- monocytes (can becomes antigen-presenting cells)

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4
Q

How does phagocytosis work?

A
  1. Phagocyte moves towards pathogen via chemotaxis
  2. Phagocyte engulfs pathogen via endocytosis to form a phagosome
  3. Phagosome fuses with lysosome
  4. Lysozymes digest pathogen
  5. Phagocyte absorbs the products from pathogen hydrolysis
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5
Q

Explain the role of antigen-presenting cells (APCs)

A
  • macrophage displays antigen from pathogen on its surface

- enhances recognition by T helper cells, which cannot directly interface with pathogens/ antigens in body fluid

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6
Q

Give 2 differences between specific and non-specific immune responses?

A
  • non-specific (inflammation + phagocytosis) is the same for all pathogens
  • specific (B + T lymphocytes) are complimentary to the pathogen
  • non-specific is immediate
  • specific has a time lag
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7
Q

Name the 2 types of specific immune response

A
  • cell mediated

- humoral

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8
Q

Outline the process of the cell-mediated response

A
  1. Complimentary T helper cells (lymphocytes) bind to foreign antigen on APC
  2. This stimulates:
    - Clonal expansion of complimentary T helper cells, become memory cells or trigger humoral response
    - Clonal expansion of cytotoxic cells T cells, secrete enzyme perforin to destroy infected cells
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9
Q

Outline the process of the humoral response

A
  1. Complimentary T helper lymphocytes bind to foreign antigen on APC
  2. Release cytokines that stimulate clonal expansion of complimentary B lymphocytes
  3. B cells differentiate into plasma cells
  4. Plasma cells secrete antibodies with complimentary variable region to antigen
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10
Q

What is an antibody/ its structure?

A
  • proteins secreted by plasma cells
  • quaternary structure: 2 ‘light chains’ held by disulfide bridges, 2 longer ‘heavy chains’
  • binding sites on variable region of light chains have specific tertiary structure complimentary to an antigen
  • rest of the molecule known as the constant region
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11
Q

How do antibodies destroy pathogens?

A
  • formation of antigen-antibody complex results in agglutination
  • activation of complement
  • opsonisation, marks microbes for phagocytosis
  • precipitation/neutralisation, makes toxins insoluble
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12
Q

What are memory cells?

A
  • Specialised T helper/ B cells produced from primary immune response
  • Remain in low levels in the blood
  • Can divide very rapidly by mitosis if organism encounters the same pathogen again
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13
Q

What are histamines?

A

chemicals released by the tissues in response to an allergic reaction

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14
Q

What’s a phagosome?

A

the vesicle in which a pathogen is enclosed in a phagocyte

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15
Q

What are cytokines?

A

cell signalling molecules with several roles in the immune system, including stimulating other phagocytes to move to the infection site

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16
Q

What are opsonins?

A

chemicals which bind to pathogens and label them so they are more easily recognised by phagocytes

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17
Q

What is an antibody?

A

a glycoprotein that is produced in response to a specific antigen

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18
Q

What are lymphocytes?

A

granulocytes made in the white bone marrow of long bones, that make up the main cellular components of the immune system

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19
Q

Where are B cells made?

A

the bone marrow

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20
Q

Define B cells

A

lymphocytes made in the bone marrow which are found both in the lymph glands and free in the body once they are mature

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21
Q

What are immunoglobulins?

A

antibodies

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22
Q

What are B effector cells?

A

divide to form the plasma cell clones

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23
Q

What are plasma cells?

A

plasma cells produce antibodies to particular antigens at a rate of around 2000 antibodies per second

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24
Q

What are B memory cells?

A

B memory cells provide the immunological memory to a specific antigen, allowing the body to respond quickly if you encounter a pathogen carrying the same antigen again

25
Q

What are T cells?

A

lymphocytes made in the bone marrow that mature and become active in the thymus gland

26
Q

What are T killer cells?

A

lymphocytes that produce chemicals that destroy pathogens

27
Q

What are T helper cells?

A

lymphocytes involved in the process that produces antibodies against the antigens on a particular pathogen

28
Q

What are T memory cells?

A

very long-lived cells which make up part of the immunological memory

29
Q

What is the major histocompatibility complex (MHC)?

A

proteins that display antigens on the cell surface membrane

30
Q

What is an antigen-presenting cell (APC)?

A

a cell displaying an antigen/MHC complex

31
Q

Define clonal selection

A

the selection of the cells that carry the right antibody for a specific antigen

32
Q

What are plasma cell clones?

A

clones of identical cells that all produce the same antibody

33
Q

Define agglutination

A

the clumping of cells caused when antibodies bind to the antigens on pathogens

34
Q

Define opsonisation

A

the process that makes a pathogen more easily recognised, engulfed and digested by phagocytes

35
Q

Define neutralisation

A

the action of antibodies in neutralising the effects of bacterial toxins on cells by binding to them

36
Q

What is a clone?

A

a group of identical cells all produced from one cell

37
Q

Describe how macrophages present antigens to T helper cells

A

-antigen on surface of macrophage binds to receptor on T helper cell

38
Q

Describe how B cells are activated

A
  • antigen binds to B cell
  • antigen binds to MHC
  • T helper cells bind to B cell
  • cytokines released from T cells
39
Q

What are the types of immunity?

A
  • artificial active
  • artificial passive
  • natural active
  • natural passive
40
Q

Define natural active immunity

A

when the body provides its own antibodies to an antigen encountered naturally

41
Q

Define natural passive immunity

A

when antibodies made by a mother are passed to the baby via the placenta or breast milk

42
Q

Define artificial active immunity

A

when the body produces its own antibodies to an antigen acquired through vaccination

43
Q

Define artificial passive immunity

A

when antibodies are extracted from one individual and injected into another e.g. tetanus vaccine

44
Q

Define immunisation

A

the process of protecting people from infection by giving them passive or active artificial immunity

45
Q

What is a vaccination?

A

the introduction of harmless forms of organisms or antigens by injection to produce artificial immunity

46
Q

Define herd immunity

A

produced when a high proportion of a population is immune to a pathogen, usually by vaccination, lowering the risk of infection to all, including the unvaccinated, as they are less likely to encounter the pathogen

47
Q

State the pros of vaccination

A
  • children protected against diseases which could kill or disable them otherwise
  • society benefits as pool of infection is reduced through herd immunity, which protects those who cannot get vaccinated due to allergies or immune system diseases
  • cost of treating serious diseases or the damage they cause is minimised for a small financial expense
48
Q

State the cons of vaccination

A
  • some live, attenuated vaccines are cultured in eggs, people with allergies can’t have them
  • minority of children become very ill and may die
  • suggested that mass vaccination is linked to rise in childhood asthma and allergies
  • some vaccines given for societal benefit
49
Q

Define attenuated pathogens

A

viable pathogens that have been modified so that they do not cause disease but still cause an immune response that results in the production of antibodies and immunity

50
Q

What are 3 non-specific responses of the immune system?`

A
  • inflammation
  • fever
  • phagocytosis
51
Q

How is inflammation effective?

A
  • histamines cause blood vessels to dilate which causes local heat and redness, local heat reduces pathogen reproduction
  • histamines cause capillary walls to become leaky, plasma with leucocytes + antibodies are forced out causing damage and pain and disables pathogens
52
Q

In inflammation, how are histamines releases?

A

when tissue is damaged, mast cells and basophils release histamines

53
Q

When is a fever not effective?

A

when body temperature rises above 40 degrees, some enzymes denature and dangerous dehydration can occur

54
Q

Why is a fever an effective response?

A
  • raised temperatures reduces the ability of pathogen reproduction
  • specific immune system works better at higher temperatures, so more successful at fighting infection
55
Q

How does a fever work in viral infections?

A

as each virus bursts out of the cell, the temperature spikes and then returns to normal

56
Q

How does a fever work in bacterial infections?

A

temperature rises steadily and stays high until successful treatment or the body overcomes it

57
Q

Why does the body temperature rise during an infection?

A

when a pathogen enters it causes the hypothalamus to reset which maintains the usual body temperature. =it is rest to a high temperature

58
Q

Describe how a B cell is activated

A
  • antigen binds to B cell
  • antigen binds to MHC
  • T helper cells bind to B cell
  • cytokines released from T helper cells
59
Q

Suggest how a microscope slide could be prepared to observe cell division in B cells

A
  • sample of B cells taken from lymph node
  • stain the cells using acetic orcein
  • heat and add HCL
  • look for the stages of mitosis

A Level Biology (32 decks)

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