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Immune System 15 Flashcards

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1
Q

What is the immune system?

A

A versatile defence system that protects us from pathogenic microbes

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2
Q

Facts about the first line of defence

A

Innate immunity
Physical barrier created by the skin and mucous membranes

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3
Q

Facts about the second line of defence

A

Innate immunity
Non-specific immune response that includes immune cells, proteins, fever and inflammation

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4
Q

Facts about the third line of defence

A

Specific / adaptive immunity
Activated by innate immune system
Specific response to a specific pathogen

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5
Q

What is a pathogen

A

An infectious agent that can cause disease in a host

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6
Q

How can pathogens enter the body?

A

Breaks in the skin
The respiratory system
The digestive system
Reproductive system
Eyes

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7
Q

What is an antigen

A

A substance that can be recognised by leukocytes

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8
Q

What are the two types of antigen

A

Foreign antigens
Self-antigens

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9
Q

What are antigens normally made from

A

Proteins

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10
Q

What are antibodies

A

Proteins that are produced in response to a specific antigen. They combine with these specific antigens

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11
Q

What are the two main first lines of defence?

A
  1. the skin
  2. mucus membranes
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12
Q

How is the skin a first line of defence?

A

It’s a physical barrier with layers of tightly-packed epithelial cells.

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13
Q

What accessory structures does the dermis contain that have an immenue function

A

Sweat glands
Sebaceous glands

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14
Q

What is the immune function of sweat

A

Removes microbes from skin
Contains IgA

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15
Q

What is the immune function of sebum?

A

Contains fatty acids that inhibit microbial growth

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16
Q

Where do you find mucus membranes?

A

In the digestive, respiratory and urogenital tracts plus the conjunctive in the eyes

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17
Q

What washes away secretions in the mucus membranes?

A

Saliva, tears and mucus secretions

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18
Q

What is the mucociliary escalator and where is in found?

A

In the respiratory tract
Cilia propel foreign substances towards the pharynx where they are swallowed

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19
Q

How does the nose defend against pathogens?

A

Hairs filter air

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20
Q

How does the vagina protect against pathogens

A

It’s acidic

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21
Q

How does the gastric tract protect against pathogens

A

Acidity
Microflora outcompete pathogens
Excretion of urine and faeces expels microbes
Vomiting and diarrhoea are rapid means of expelling pathogens

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22
Q

When pathogens penetrate the physical and chemical barriers what do they encounter next?

A

The second line of defence

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23
Q

List some elements of the second line of defence?

A

Complement system
Transferrins
Phagocytes
Natural killer cells
Inflammation
Cytokines - eg interferons
Fever

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24
Q

What are transferrins and how do they work?

A

Iron-binding proteins in the blood - inhibit the growth of certain bacteria by reducing the amount of available iron.

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25
What is the complement system and where is it made?
A defense system of over 30 proteins made by the liver
26
What happens when complement proteins are activated?
They act in a cascade (they are amplified)
27
What is the most common mechanism that complement proteins are activated?
'Classical pathway' where antigen-antibody complexes are formed
28
What are the three stages for complement proteins to destroy microbes?
1. promote phagocytosis - coat microbes in a process called opsonisation which promotes the attachment of a phagocyte to a microbe 2. promote inflammation - bind to mast cells to release histamine 3. cause cytolysis by destroying microbes
29
What is opsonisation
In the complement system when a fragrame coats a microbe to promote the attachment of a phagocyte to the microbe
30
What are cytokines?
Small protein hormones that stimulate or inhibit normal cell function
31
What are cytokines secreted by?
Leukocytes
32
Name three types of cytokines
Interleukins Interferons Tumour necrosis factor
33
What do interleukins do?
Mediators between leukocytes - mostly produced by T-helper cells
34
What do interferons do?
Involved in anti-viral responses
35
What does tumour necrosis factor do?
Promotes accumulation of neutrophils and macrophages to cause cell death
36
How do interferons work?
They interfere with viral replication Attach and penetrate a cost cell to prevent it replicating
37
What is phagocytosis
Cell digestion
38
What attracts phagocytic cells to sites of inflammation
Chemotaxis
39
2 major types of phagocytes?
Macrophages (monocytes in blodd) and neutrophils
40
Are phagocytes selective
no
41
What type of phagocyte is also an antigen presenting cell?
Macrophages
42
Two types of macrophages
Wandering and fixed
43
Where can you find fixed macrophages?
Histiocytes Kupffer cells Alveolar Microglia - nervous tissue Langerhands - skin Tissue macrophages - spleen, bone marrow and lymph nodes
44
5 stages of phogocytosis
1. chemotaxis - release chemicals to activate complement and attract phagocytes 2. Adherence - of phagocyte to target 3. Ingestion - engulf microbe 4. Digestion - lysozymes and digestive enzymes 5. Excretion - of indigestible material
45
What are natural killer cells
Non-specific lymphocytes The account for 5-10% of lymphocytes
46
Where do you find natural killer cells
Blood, lymph nodes, spleen and bone marrow
47
What do natural killer cells do?
They attack anything they don't recognise
48
How do natural killer cells perform phagocytosis?
Realease granules called perforin Perforin inserts into the cell membrane and create a channel for tissue fluid which causes cytolysis
49
What is inflammation
A non-specific defensive response to tissue damage
50
What can cause inflammation?
Pathogens, abrasions, chemicals, cell distortion, extreme temperature
51
Is inflammation specific
No - it's non-specific so the response to different insults is the same
52
What are the five cardinal signs of inflammation
Redness heat pain swelling loss of function
53
What are the first stage of inflammation
1. vasodilation and increased permeability - allows additional blood to the area Increased permeability permits movement of immune cells Together these create redness, swelling and heat.
54
Why does inflammation create pain
Pain is the result of injury from neurons and toxic chemicals
55
What is the second stage of inflammation
Emigration of phagocytes (via chemotaxis) Neutrophils squeeze through vessal wall Monocytes follow Dead phagocytes accumulate as puss
56
What is stage three of inflammation
Tissue repair
57
What do inflammatory mediators do?
Coordinate the inflammatory response
58
4 inflammatory mediators
Histamine Leukotrienes Kinins Prostaglandins
59
Where does histamine come from and what does it do?
Released by mast cells and basphils - causes vasodilation and increased permeability
60
Where do leukotrienes come from and what do they do?
Released by basophils and mast cells. Attract phagocytes and increase vessel permeability
61
What are kinins and what do they do?
Proteins that induce vasodilation and increased permeability
62
What are prostaglandins and what do they do?
Lipids from damaged cells Enhance effects of histamine and kinins - intensify pain
63
What are the benefits of inflammation x 4
Promotes phagocytosis Promotes immune response Dilutes toxins Fibrin formation - helps bind wounds
64
Harmful effects of inflammation x 4
Swelling Pain Adhesions and scar tissue Atherosclerosis
65
4 possible outcomes of inflammation
1. resolutions 2. chronic inflammation 3. granuloma - cellular attempt to contain foreign body 4. fibrosis - scar tissue formation
66
What is a fever
Abnormally high body temperature
67
Why happens in the body when you get a fever
Hypothalamus thermostat is reset Many bacterial toxins elevate body temperature - release fever causing cytokines such as interleukin-1 Interleukin-1 induces a fever
68
What does an elevated body temperature do?
Makes interferons more effective Inhibits growth of some microbes Speeds up reactions that aid repair
69
6 leukocytes
1. Basophils and mast cells 2. eosinophils 3. neutrophils 4. monocytes and macrophages 5. natural killer cells 6. B and T lymphocytes
70
Facts about basophils and mast cells
In blood basophils in blood mast cells Release histamine - vasodilates and heparin Receptors for IgE
71
Facts about Eosinophils
Destroy parasitic worms via phagocytosis
72
Facts about Neutrophils
60% of leukocytes Phagocytic Granules release lysozymes that digest debris
73
Facts about monocytes and macrophages
Blood monocytes Tissue - macrophages Phyagocytic and secrete cytokines e.g interleukin-1 and TNF
74
Facts about natural killer cells
Target foreign cells, secrete perforin to induce cytolysis
75
B and T lymphocytes
Adaptive (specific) immunity and immunological memory
76
What can B and T lymphocytes do as part of the third line of defence?
Possess specificity for antigen - recognise self from non-self Produce immune memory Allows quicker and more effective attack with next encounter
77
What are cytokines?
Messenger molecules that mediate the connection between innate immune system and adaptive immune system
78
What are the effector cells of the adaptive immune system?
T and B lymphocytes
79
What does MHC stand for?
Major histocompatibility complex
80
What are major histocompatibility complexes?
Group of cell-surface proteins that allow the immune system to differentiate healthy body cells from non-self
81
What is the structure of major histocompatibility complex
4 polypeptide chains Display a protein produced by the cell
82
What is major histocompatibility complex I
Located in all body cells except erythrocytes Abnormal proteins mix with MHC-I to display flags on the cell surface
83
What is major histocompatibility complex II
Located only on the cell membrane of antigen presenting cells - macrophages and B-lymphocytes
84
What does major histocompatibility complex II present antigens to?
T-helper cells
85
What do T lymphocytes do?
Each t-lymphocyte has a unique t-cell receptor that only recognises a specific antigen
86
Where are T lymphocytes produced and where do they mature?
Produced in bone marrow Mature in thymus
87
What are the two types of T-cell?
T-helper cells Cytotoxic t-cells
88
What are t-helper cells also known as?
CD4 cells
89
What are cytotoxic t-cells also known as
CD8 cells
89
What to traits must t-cells have?
Self-recognition and self-tolerance
90
What does loss of self-tolerance lead to?
Autoimmunity
91
What is adaptive immunity
Body's ability to defend itself against specific agents
92
What are the two types of adaptive immunity
cell-mediated and anti-body mediated
93
Facts about cell-mediated immunity
By t-lymphocytes Cytotoxic t-cells attack antigens Mostly against intra-cellular pathogens
94
Facts about anitbody-mediated immunity
By B-lymphocytes Secrete specific antibodies Mostly defend against extra-cellular pathogens

Biomedicine (20 decks)

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