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12 biology > Lines of Defence > Flashcards

Lines of Defence Flashcards

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1
Q

what are antigens?

A

Molecules or parts of molecules
Recognised by T lymphocytes or antibodies produced by B lymphocytes
Bound to the surface or or secreted by B L
Allow body to recognise pathogens and organised an immune response (immunogens)

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2
Q

what are antigens made of?

A

Most made of proteins but also made of carbohydrates, lipids and nucleic acids

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3
Q

where are antigens? self and non-self?

A

On the surface of cells: recognition sites for the immune system
Others such as toxins from bacteria circulate through the body fluids
Immune system can usually distinguish between those made by its cells (self-antigens) and those that aren’t (non-self) and respond accordingly

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4
Q

how is an antigen responded to? BL and TL? how do they differentiate between self and non-self?

A

Must be detected by receptors
Receptors on BL are MB antibodies that recognise free antigens or those on the surface of pathogens
Receptors on TL recognised antigens from the organism’s cells
Receptors are specific
Major histocompatibility complex proteins or human leukocyte antigens are proteins on surface of cells that present their self or non-self antigens to TL
In the thymus, TL mature (positive selection)
First stage: if the don’t interact with MHC they are destroyed by apoptosis
Second stage (negative selection): TL that react with self antigens bind to the cells in the thymus and die
Process is called clonal deletion
Inability to respond to self antigens is called self-tolerance and results in an autoimmune disease

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5
Q

what are allergens?

A

antigens that elicit an allergic immune response

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6
Q

what are pathogens?

A

agents that cause disease

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7
Q

what are primary pathogens?

A

cause disease anytime they are present.

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8
Q

what are opportunistic pathogens?

A

only cause disease if the host’s defences are low

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9
Q

how are pathogens detected?

A

Usually have unique antigens that immune system detects

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10
Q

what are the cellular pathogens?

A

bacteria, fungi, oomycetes, protozoans, worms and anthropods

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11
Q

describe bacteria?

A

Prokaryotes
Not always pathogenic- can benefit from them
Can cause infection

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12
Q

describe fungi? what part causes disease? how does the immune system detect them?

A

Macroscopic (mushrooms) to microscopic (moulds, unicellular yeasts, yeast-like fungi)
Secrete digestive enzymes and chemicals to break down matter (then reabsorbed)
These substances can cause disease
Fungal cells produce surface glycoproteins and polysaccharides that acts as antigens and are detected by the immune system

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13
Q

what are oomycetes? how do they cause disease?

A

Protista
Cause blight and mildew in plants
Infections in animals
Motile cells, walls of cellulose (not like fungi)
Can swim in water to other leaves or a germination site
Can Germinate directly sending a hypha (fungal thread) that invades plant tissue, absorbing nutrients to digesting the cytoplasm with enzymes to release molecules that can be absorbed
In plants can suppress the host’s immune system to cause apoptosis

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14
Q

what are protozoans? how do they remain undetected?

A

Unicellular eukaryotes
Reproduce inside cells or extracellular
Can express different proteins on their surface at different stages of life (acts as antigens)

Antigenic variation: change of surface proteins; helps to evade detection by the host

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15
Q

what worms infect? how do they affect animals?

A

Parasitic worms can infect plants and animals
Flatworms such as tapeworms and round worms such as hook, pin and thread worms
In plants, round worms infect roots
In animals, parasitic worms can suppress the immune system eg. Blocking enzymes needed for antigen presentation

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16
Q

what are anthropoids? how do they cause disease?

A

Invertebrates with an exoskeleton
Transmit or cause disease
Mosquitoes, ticks, lice, mites
Saliva can modulate host immune response and inhibit inflammation- create a favourable environment for pathogen transmission
Saliva also contains antigens that trigger an adaptive immune response (investigated for vaccines against vector-borne diseases)
Can damage plants with saliva etc.

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17
Q

what are the non-cellular pathogens?

A

viruses, viroids and prions

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18
Q

what are viruses made of? how do they go undetected?

A

Composed of DNA or RNA composed in a protein coat and sometimes also a lipoprotein envelope
In antigenic drift they make minor changes to their surface antigens which result in genetic changes that are similar.
Eventually these changes add up and make the virus quite different
Usually detected
Antigenic shift is a major change resulting in very different antigens

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19
Q

what are viroids? what do they affect? how?

A

Type of self-cleaving RNA enzyme (or ribosome) that is made of short, circular strands of RNA that lack a protein coat
Only pathogens of plants
Damage plants by competing for nucleotides and forming viroid bundles, which interfere with the internal structures like a tumour

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20
Q

what are prions? how do they effect? what do they cause? symptoms?

A

Smaller than viroids
Do not contain genetic material
Proteins that are similar to cellular prion proteins (PrP) which are found in the central nervous system but they have abnormal shape
Stimulate PrP to misfiled into infectious prions
Resistant to being denatured as well as being broken down by proteases
Cause neurodegenerative diseases in mammals
Causes CJD in humans by misfiling plaques which kills neurons and makes the brain appear spongy
Symptoms: dementia, muscle contractions, death
BSE in cows or mad cow disease- eat contaminated meat and get CJD
Prions elicit an ineffective inane immune response and adaptive immune system is unable to identify and respond
Very similar to PrP so any TL that would respond to them would have been destroyed
Or prions are unable to be broken down and presented by antigen-presenting cells

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21
Q

what is innate immunity?

A

physical, chemical and microbiological barriers that provide innate resistance to infection as well as a response to barriers that have been breached.

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22
Q

what are the barriers to infection?

A

physical, chemical, microbiological

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23
Q

physical barriers in plants

A

Cell walls, cuticle (on the outer cell wall), bark, stomata which are closed when signalled
Vertical leaves means water cannot collect which prevents water-motile pathogens

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24
Q

physical barriers in animals

A

Epithelial cells lines skin, respiratory, gastrointestinal and urogenital tracts and are joined by membrane proteins that create a continuous barrier
Toughened (keratinised) skin, mucus, cilia

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25
Q

chemical barriers in plants? an example

A

saponin from wheat which disrupts membranes of fungi

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26
Q

chemical barriers in animals? external; and internal

A

External chemical barriers include lysozyme enzymes and toxic metabolites (eg. Lactic acid and fatty acids found in tears, sweat and saliva)- destroy cell walls
Internal chemical barriers such as stomach acid and digestive enzymes can kill pathogens
Fluid in lungs contains surfactants which coat pathogens, making it easier for macrophages
Vagina is coated with acidic secretions that defend against pathogens

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27
Q

microbiological barriers in animals

A

Non-pathogenic bacteria (normal flora)
On skin, throat, lower gastrointestinal tract, urogenital tract
Prevents growth and colonisation of other bacteria because of competition and secretion of chemicals that lowers pH
Antibiotics can disrupt normal flora and make the person susceptible to infections

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28
Q

what does the innate immune response do?

A

If can’t eliminate the pathogen, keeps them under control until third line of defence

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29
Q

features of the innate immune response?

A 
Non-specific- don’t target a specific antigen
Rapid
Present in all animals
Fixed responses- no adaption
Do not cause immunological memory
30
Q

what are phagocytes? what do they do? examples? how do they work? APC?

A

Leukocytes
Engulf and break down pathogens by phagocytosis
neutrophils, macrophages, monocytes, dendritic cells
TLRs on phago interact with PAMPs, signal transduction, leads to activation of phagocyte which engulfs
Plasma membrane forms vacuole around pathogen (phagosome)
Lysosome fuses with phagosome forming phagolysosome which breaks its down
Fragments are expelled by exocytosis
Macrophages and dendritic cells are antigen-presenting cells- fragments are displayed on the surface (linked to MHC-1 proteins)

31
Q

where are MHC I and MHC II found and what do they do? absence?

A

MHC-I and II are involved in antigen presentation
MHC-I present antigens from pathogens to cytotoxic T lymphocytes
Absence allows natural killers to identify infected or damaged cells
MHC-II are most commonly found on APCs and their presentation activates helper TL

32
Q

what is a neutrophil? what does it do?

A

Phagocytosis
Release defensins that disrupt fungi and bacterial membranes
Release cytokines that attract other immune cells and cause inflammation

33
Q

what is a macrophage? what does it do?

A

Phagocytosis
Antigen presentation
Release cytokines

34
Q

what is a monocyte?

A

Phagocytosis

35
Q

what is a dendritic cell?

A

Phagocytosis

Antigen presentation

36
Q

what is a basophil?

A

Release histamines

Some phagocytosis

37
Q

what is an eosinophil?

A

Antigen presentation
Release cytokines
Some phagocytosis

38
Q

what is a mast cell?

A

Role in inflammation by releasing histamines

Some phagocytosis

39
Q

what is a natural killer?

A

Recognise virus infected and cancerous cells
Punch holes in cells which begins apoptosis
Release cytokines

40
Q

what are the defence molecules?

A

complement proteins, cytokines

41
Q

what are complement proteins? how do they activate? what do they do?

A

Help kill pathogens
Activated by antigens
Use enzymes to to lyse pathogens
Punch holes in membranes, bacterial contents attracting phagocytes

42
Q

what are cytokines? what do they do? when are they released? types?

A

Signalling molecules
Activate aspects of immune response
Released in response to damage or infection
Trigger specific and non-specific responses
- interferons and chemokine

43
Q

interferons? produced by? what do they do?

A

Produced by and act on cell with virus
Causes a stop to translation- limits viral replication and release from cell
Attract NK that kill the infected cell
Non-specific- act on any virus
Some viruses can evade or inhibit interferons

44
Q

what is a chemokine?

A

Act as attractants

Attract leukocytes

45
Q

what is inflammation?

A

accumulation of fluid, plasma proteins and leukocytes that occurs in damaged or infected tissue and results in heat, swelling, redness and pain.

46
Q

what are the steps that cause inflammation?

A

Pathogens breach first line of defence
Injured cells release cytokines that attract neutrophils. Mast cells release histamine that dilates blood vessels and permeability allowing leukocytes and complement proteins in. Platelets release clotting factors.
Neutrophils recruit macrophages and secrete defensins
Macrophages secrete cytokines and phagocytosis. May lead to pus, which contains leukocytes, dead cells and cell debris.
Inflammatory response continues until pathogen is eliminated and wound healed.

47
Q

what is fever? why?

A

Set point in hypothalamus increased by inflammatory cytokines
Temp increase
Slows replication of bacteria and viruses so allows for more defences to intervene
Can increase proliferation of leukocytes (to a certain point).

48
Q

what is the nature of the adaptive immune response?

A

Specific: responds to specific antigens

Immunological memory: remember antigens and have a larger, more rapid second response

49
Q

receptors on lymphocytes? what types? what do they do?

A

Each has a different receptor for a specific antigen
Proliferates, creating clones of the initial with the same receptors (clonal selection)
B or T
Travel through the lymph system and are activated when they encounter specific antigens

50
Q

what are the mechanisms of the adaptive immune response?

A

humoral or cell-mediated

51
Q

humoral immunity?

A

complement proteins and antigens produced by B are secreted into extracellular fluid

52
Q

cell-mediated immunity?

A

actions of T and phagocytes

53
Q

what is the summary of humoral immunity?

A

Antibodies are released into blood and lymph by B

54
Q

where do BL originate? where do they mature? where are they located? what do they do? what do they divide into?

A

Originate and differentiate in bone marrow
Mature in lymph organs
Billions in blood
Bind to specific antigens and are activated to proliferate
Cytokines from T helpers help with activation
Divide into plasma cells and memory B lymphocytes

55
Q

plasma cells? what do they do? features of antibodies? how many antibodies?

A

Produce antibodies
Antibodies are specific to the antigen that activated the B
Thousands of antibodies a second

56
Q

what are memory BL? where? what do they do?

A

Stay in lymphoid tissues
Immunity after infection or vaccination
Divide and give rise to plasma cells if exposure to antigen occurs again

57
Q

antibodies? another name? produced by? where? what do they do? structure? how do they act?

A

Aka immunoglobulins
Produced by B and released into blood and lymph
Bind to specific antigens
Structure: two long heavy chains and two short light chains, top are variable regions which allows different antigens to bind. Constant region is the ‘stem’ of the Y and is the same
Act singly (monomers, in pairs (dimers) or in groups of 5 (pentamers)

58
Q

what do antibodies do in functioning? NAP

A

Neutralisation: bind to bacterial toxins, blocking their actions
Neutralisation: bind to antigens on the surface of pathogens which are required for entry into host cells, preventing invasion
Agglutination: bind to antigens on cells and form antigen-antibody complexes, which activate phagocytes and the complement cascade, leading to antigen or cell destruction
Precipitation: antibodies bind to soluble antigens, causing them to become insoluble.

59
Q

what are helper TL?

A

Secrete cytokines that promote inflammation and activate macrophages and B

60
Q

what do cytotoxic TL do?

A

Recognise and kill foreign, infected or abnormal cells by releasing toxins

61
Q

what do memory TL do?

A

Produced after helper and cytotoxic have been activated
They then differentiate into memory that are antigen-specific
Ensure a prompt response if the antigen returns

62
Q

T cell receptors? where do they bind? what does this do?

A

Central to the function of T cells
TCRs have one antigen binding site
Bind to antigen fragments on APCs
This triggers signal transduction in T cell, resulting in proliferation and cytokine release and activation of cytotoxic function

63
Q

how does antigen recognition by TL work?

A

T cells check antigens on cells they come into contact with detecting self and non-self
These antigens are made by those cells and are on MHC-I markers
APCs present fragments of pathogen antigens on MHC-II markers
TCRs recognise the antigen-MHC-II complex

64
Q

what is immunological memory?

A

Existing memory cells mean a second exposure is responded to faster and larger
Some antibodies may exist from the first exposure

65
Q

what does the lymphatic system do?

A

Returning fluid back to circulatory system
Transporting fatty acids and fats from digestive system
A place for lymphocytes to mature
Transporting lymphocytes and antigen-presenting cells to lymph nodes stimulating adaptive immune response
Trapping pathogens in lymph nodes where they are destroyed (why swell up)

66
Q

what is the lymphatic system made up of?

A

Lymphatic system made of lymph, lymphatic vessels, organs and tissues

Lymph: when fluid surrounding tissues is drained into lymphatic vessels it is considered lymph. It contains lymphocytes and phagocytes.

Lymphatic capillaries—> larger vessels that empty into veins near heart
One-way-valves
Movement is what moves lymph- inactive = swelling
Movement of substances between circulatory and lymphatic by extravasation

67
Q

what are the primary lymphoid organs?

A

Bone marrow and thymus
Bone marrow makes blood cells
Thymus has a role in TL maturation.

68
Q

what are the secondary lymph organs?

A

lymph nodes, spleen,

69
Q

what do the lymph nodes do? what occurs here?

A

Act as filters, collecting foreign particles, waste, toxins and pathogens
APC present antigens to TL in lymph nodes
BL that identify antigens undergo clonal expansion and differentiate to plasma cells
Antibody is released into the bloodstream
Cytotoxic TL are activated, proliferate and travel to where needed

70
Q

what does the spleen do? what does it store?

A

Control number of red blood cells by destroying them
Stores lymphocytes
Site of BL maturation but can mature in other secondary lymphoid organs

12 biology (13 decks)

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