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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
chemical barriers in plants? an example
saponin from wheat which disrupts membranes of fungi
26
chemical barriers in animals? external; and internal
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
27
microbiological barriers in animals
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
28
what does the innate immune response do?
If can’t eliminate the pathogen, keeps them under control until third line of defence
29
features of the innate immune response?
``` Non-specific- don’t target a specific antigen Rapid Present in all animals Fixed responses- no adaption Do not cause immunological memory ```
30
what are phagocytes? what do they do? examples? how do they work? APC?
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
where are MHC I and MHC II found and what do they do? absence?
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
what is a neutrophil? what does it do?
Phagocytosis Release defensins that disrupt fungi and bacterial membranes Release cytokines that attract other immune cells and cause inflammation
33
what is a macrophage? what does it do?
Phagocytosis Antigen presentation Release cytokines
34
what is a monocyte?
Phagocytosis
35
what is a dendritic cell?
Phagocytosis | Antigen presentation
36
what is a basophil?
Release histamines | Some phagocytosis
37
what is an eosinophil?
Antigen presentation Release cytokines Some phagocytosis
38
what is a mast cell?
Role in inflammation by releasing histamines | Some phagocytosis
39
what is a natural killer?
Recognise virus infected and cancerous cells Punch holes in cells which begins apoptosis Release cytokines
40
what are the defence molecules?
complement proteins, cytokines
41
what are complement proteins? how do they activate? what do they do?
Help kill pathogens Activated by antigens Use enzymes to to lyse pathogens Punch holes in membranes, bacterial contents attracting phagocytes
42
what are cytokines? what do they do? when are they released? types?
Signalling molecules Activate aspects of immune response Released in response to damage or infection Trigger specific and non-specific responses - interferons and chemokine
43
interferons? produced by? what do they do?
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
what is a chemokine?
Act as attractants | Attract leukocytes
45
what is inflammation?
accumulation of fluid, plasma proteins and leukocytes that occurs in damaged or infected tissue and results in heat, swelling, redness and pain.
46
what are the steps that cause inflammation?
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
what is fever? why?
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
what is the nature of the adaptive immune response?
Specific: responds to specific antigens | Immunological memory: remember antigens and have a larger, more rapid second response
49
receptors on lymphocytes? what types? what do they do?
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
what are the mechanisms of the adaptive immune response?
humoral or cell-mediated
51
humoral immunity?
complement proteins and antigens produced by B are secreted into extracellular fluid
52
cell-mediated immunity?
actions of T and phagocytes
53
what is the summary of humoral immunity?
Antibodies are released into blood and lymph by B
54
where do BL originate? where do they mature? where are they located? what do they do? what do they divide into?
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
plasma cells? what do they do? features of antibodies? how many antibodies?
Produce antibodies Antibodies are specific to the antigen that activated the B Thousands of antibodies a second
56
what are memory BL? where? what do they do?
Stay in lymphoid tissues Immunity after infection or vaccination Divide and give rise to plasma cells if exposure to antigen occurs again
57
antibodies? another name? produced by? where? what do they do? structure? how do they act?
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
what do antibodies do in functioning? NAP
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
what are helper TL?
Secrete cytokines that promote inflammation and activate macrophages and B
60
what do cytotoxic TL do?
Recognise and kill foreign, infected or abnormal cells by releasing toxins
61
what do memory TL do?
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
T cell receptors? where do they bind? what does this do?
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
how does antigen recognition by TL work?
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
what is immunological memory?
Existing memory cells mean a second exposure is responded to faster and larger Some antibodies may exist from the first exposure
65
what does the lymphatic system do?
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
what is the lymphatic system made up of?
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
what are the primary lymphoid organs?
Bone marrow and thymus Bone marrow makes blood cells Thymus has a role in TL maturation.
68
what are the secondary lymph organs?
lymph nodes, spleen,
69
what do the lymph nodes do? what occurs here?
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
what does the spleen do? what does it store?
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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