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Biology A Level > Immunity > Flashcards

Immunity Flashcards

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1
Q

the immune system

A
  • combats infective agents
  • recognises and rejects foreign cells and tissues
  • specific and non-specific
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2
Q

non-specific immune system (innate)

A
  • first and second lines of defense
  • primary defences
  • skin
  • mast cells + basophils
  • histamine
  • phagocytes
  • complement proteins
  • cytokines
  • tears and mucus
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3
Q

primary defences

A
  • present from birth
  • quick-acting
  • effective against a wide range of pathogens and foreign substances
  • always same response
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4
Q

skin

A
  • first natural barrier to infection
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5
Q

mast cells and basophils

A
  • large mobile cells

- release histamine

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6
Q

histamine

A

causes inflammation response

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7
Q

phagocytes

A

large white blood cells which engulf foreign substances

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8
Q

complement proteins - general

A

blood proteins contributing to breakdown and removal of pathogens

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9
Q

cytokines

A

small protein molecules

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10
Q

tears and mucus

A

contain lysozymes

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11
Q

histamines

A
  • dilate arterioles
  • cause diapedesis
  • increase tissue fluid formation
  • sensory neurones become more sensitive
  • activates complement proteins in plasma
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12
Q

complement proteins - specific

A
  • attract phagocytes to site of reaction
  • act as opsonins
  • bind to, and form pores in, the surface of foreign cells
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13
Q

monocytes

A
  • loads!
  • migrate into tissues
  • mature into macrophages
  • can renew lysosomes
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14
Q

phagocytosis

A

1) phagocyte attracted to pathogen (due to chemical products of pathogen)
2) phagocyte CSM receptors attach to antigens on pathogen surface
3) pathogen engulfed to form phagosome
4) lysosomes move towards and fuse with phagosomes
5) lysozyme enzymes hydrolyse pathogen molecules
6) soluble products absorbed into cytoplasm or expelled from cell

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15
Q

specific immune response (adaptive)

A
  • blood and lymph cells and proteins that attack, disarm, destroy and remove foreign substances
  • responds slowly
  • only effective against specific pathogens
  • activated by antigens
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16
Q

B cells

A
  • mature in bone marrow

- migrate to lymph nodes

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17
Q

T cells

A
  • mature in thymus gland

- migrate to lymph nodes

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18
Q

immunological memory

A

immune response is sped up on repeated infection with the same pathogen

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19
Q

antigens

A
  • molecules recognised as non-self, that trigger a lymphocyte immune response
  • complex of proteins or glycoproteins (each cell has several)
  • also occur in non-cellular substances
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20
Q

example of a non-cellular substances containing antigens

A

venom

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21
Q

diapedesis

A

cells in capillary walls draw away from each other

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22
Q

what does increased tissue fluid formation result in?

A

leucocytes, fluid, and antibodies increase in tissue

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23
Q

what are the two sections of the specific (adaptive) immune response?

A
  • humoural

- cell-mediated

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24
Q

what are non-self antigens?

A

antigens from foreign organisms or substances to which the body has not yet become adapted

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25
Q

lymphocytes

A
  • small leucocytes with little cytoplasm and spherical nuclei
  • originate from stem cells in the bone marrow
  • circulate in the lymph once mature
  • only activated by specific antigens
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26
Q

lymphatic system

A
  • nodes, spleen, adenoids, tonsils + bloodstream

- contains lymph

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27
Q

humoural response

A

uses soluble antibodies in the blood and lymph

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28
Q

antibody

A
  • a unique globular protein that reacts with a specific membrane-bound antigen
  • binding only occurs with complementary shape
  • produced by small lymphocytes
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29
Q

In the humoural response, several types of reaction occur…

A

… depending on the ability of the antibody to bind to the antigen

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30
Q

which small lymphocytes produce antibodies?

A

B cells

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31
Q

B cells

A
  • already exist in millions
  • countless types, each of which produce a specific antibody
  • mature in the bone marrow
  • have immunocompetence, and self detection
  • produce memory cells
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32
Q

when a B cell meets an antigen

A
  • it divides mitotically (clonal selection)

- after several generations, the cells differentiate into plasma cells

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33
Q

plasma cells

A
  • all formed from one type of B cell
  • all secrete the same antibody
  • lots of RER, Golgi and mitochondria
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34
Q

primary response

A
  • the response of the immune system to an antigen it meets for the first time
  • slow; takes days or weeks to recruit enough plasma cells to control infection
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35
Q

secondary response

A
  • involves memory cells

- rapid man

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36
Q

antibody structure

A
  • protein
  • 4 polypeptide chains (quaternary structure)
  • 2 light chains
  • 2 heavy chains (long)
  • disulphide bridges join light and heavy chains
  • constant region (same AAs)
  • variable region
  • hinge region
37
Q

variable region

A
  • variety of AAs
  • antigen binding site
  • causes antibody specificity
38
Q

How do antibodies trigger pathogen destruction?

A

1) agglutination
2) opsonisation
3) neutralisation

39
Q

agglutination

A
  • binding of antibodies causes pathogens to clump together
  • helps prevent spread
  • makes engulfing easier
40
Q

opsonisation

A
  • acts as an opsonin
41
Q

opsonin

A

a chemical which makes the pathogen more easily recognised by phagocytes

42
Q

neutralisation

A
  • antibodies neutralise the effects of bacterial toxins by binding to them
43
Q

How do antibodies tackle viruses?

A

bind to them, stopping them from attaching to the host

44
Q

immunoglobins

A
  • glycoprotein receptors on B cell membranes
  • B cells contain multiple copies of immunoglobin genes
  • genes recombine randomly during maturation, producing new unique genes for immunoglobin specificity
45
Q

cell-mediated response

A
  • occurs when pathogen is inside cell (mostly viral)
  • when cells have become antigen presenting
  • produces cells specific to invading pathogen
46
Q

How are antigen presenting cells (APCs) produced?

A
  • during infection, pathogen is digested

- antigens are bound to MHC (locus of DNA)

47
Q

T-helper cells

A
  • have particular receptor proteins on cell surface membrane, specific to antigen
  • on meeting, cell divides mitotically
  • some cells remain in blood and lymph as memory cells, others activate immune cells
48
Q

Which immune cells to T-helper cells activate?

A
  • B cells
  • phagocytes
  • Tc (cytotoxic T) cells
  • macrophages
  • Ts (suppressor T) cells
49
Q

T-killer cells

A
  • have complementary antigen-receptors
  • attack cells that have been antigenically altered or larger pathogens
  • produce perforin
50
Q

describe a large pathogen

A

e.g. a unicellular parasite

51
Q

perforin

A

punches holes in CSM

52
Q

T-suppressor cells

A
  • suppress immune responses where appropriate

- interact in antigen-specific manner with Th or B cells

53
Q

macrophages

A
  • large phagocytotoxic white blood cells which destroy pathogens
  • derived from monocytes
  • have indented nuclei
54
Q

immune communication

A

necessary because humoural and cell-mediated response work in conjunction

55
Q

cytokines

A
  • activators or inhibitors of cell signalling pathways
  • growth, differentiation and behaviour of cells
  • e.g. interferons
56
Q

interferon-alpha

A
  • regulates growth genes

- used in medicine: boosts immune system and reduces tumour growth

57
Q

monoclonal antibodies - basic

A

a single type of antibody produced by a B cell in response to a specific antigen that can be isolated and cloned

58
Q

monoclonal antibodies - specific

A
  • cloned B cell stimulated with an antigen epitope, fused with immortal malignant antibody-producing myeloma cell; hybridoma cell
  • can multiply specifically and infinitely
59
Q

general principles of monoclonal antibody use:

A
  • attach to fluorescent dyes/radioactive labels
  • also agglutinate antigens
  • shows presence and extent of infection
60
Q

pregnancy testing - how they work:

A
  • monoclonal antibodies correspond to coloured particles (blue latex)
  • hcG binds to particles
  • hcG-antibody-colour complex moves along strip
  • captured (immobilised) by another antibody to form a line
61
Q

pregnancy testing - in general:

A
  • done at home
  • non-invasive
  • reallllly early indicator
62
Q

how is a pregnancy test a really early indicator?

A

placenta produces human chorionic gonadotrophin (found in mother’s urine) when fertilised egg binds to uterine wall

63
Q

HSV1 testing

A

(3-G11) reacts with glycoprotein C complex

64
Q

HSV2 testing

A
  • 6-A6
  • 6-E12
  • 6-HII
65
Q

herpes testing allows

A

serotyping - classification based on surface antigens

66
Q

HIV testing - ELISA

A
  • HIV p24 antigens manufactured and attached to petri dish
  • wash with blood sample
  • wash unattached antibodies away
  • wash with marker antibody (specific to all human antibodies)
67
Q

describe the marker antibody in the ELISA test

A
  • black circle

- enzyme + substrate

68
Q

separation of monoclonal antibodies

A
  • antibodies immobilised on resin beads
  • mixture poured over beads
  • only target molecules attach
  • beads washed with substance that releases the molecule
69
Q

ELISA

A

enzyme-linked immunoabsorbant assay

70
Q

ADEPT acronym

A

antibody direct enzyme prodrug therapy

71
Q

ADEPT

A
  • enzyme is attached to monoclonal antibody
  • activates a drug (cytotoxic)
  • attaches to target cancer cells
  • large amount of inactive drug injected
  • prodrug remains inactive around healthy cells
72
Q

treating cancer with ADEPT

A
  • suicidal protein caused by contact inhibition allows specificity to cancer cells
  • stops blood vessel formation around tumours
  • tag with cytotoxic drug
73
Q

suicidal protein

A

blocks mitotic signals

74
Q

Limitations of monoclonal antibodies

A
  • ethics: humans cannot be immunised against antigens
  • fused human lymphocyte-mouse myeloma cells are very unstable (recognised as foreign and eliminated)
  • no suitable human myeloma cells to replace mouse
  • antigenic variability -> mutation
75
Q

ethical issues with monoclonal antibodies

A
  • mice used to produce antibodies and tumour cells involves spleen removal and emulsification
  • deaths associated with MS treatment
  • trial for TGN1412 - 6 patients had multiple organ failure (they survived)
76
Q

Why did the patients on the TGN1412 trial have multiple organ failure?

A

T cells produced chemicals overstimulating the immune response and attacked body tissue

77
Q

advantages of monoclonal antibodies

A
  • can target any molecule (including human ones)
  • don’t kill adjacent cells
  • produced in vast quantities, quickly
78
Q

uses of monoclonal antibodies

A
  • cancer treatment
  • prevention of transplant rejection
  • auto-immune treatment
  • viral treatment
79
Q

vaccinations

A
  • artificial active immunity
80
Q

active immunity

A
  • delay between infection and full immune response

- vulnerable to toxins

81
Q

attenuation

A
  • weakening of pathogens

- culturing anaerobically away from temperature optimum

82
Q

toxoids

A
  • inactivated toxins

- no deleterious side-effects

83
Q

herd immunity

A
  • vaccinations administered to a large number of people at the same time
  • results in general immunity
  • reduces risk of encountering an infectious agent
84
Q

why might vaccines be ineffective?

A
  • inherited defective immune system

- defences weakened by infections/malnutrition

85
Q

antigenic drift

A

small changes in pathogen antigens

86
Q

antigenic shift

A

large changes in pathogen antigens

87
Q

artificial passive immunity

A

ready-made antibodies against a toxin

88
Q

natural passive immunity

A
  • occurs when a fetus is still in the uterus
  • maternal antibodies cross the placenta into fetal blood
  • temporary; antibodies broken down by spleen and liver
  • no immunological memory
89
Q

what does natural passive immunity not give any immunological memory

A

because the baby did not make the antibodies itself

Biology A Level (45 decks)

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