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Biomed2 > Immune System > Flashcards

Immune System Flashcards

1
Q

What is the immune system

A

A versatile defence system that protects us from pathogenic microbes
With 3 main lines of defence

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2
Q

First line of defence

A

“Innate immunity”

Physical barrier ie skin & mucous membranes

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3
Q

Second line of defence

A

“Innate immunity”
Non-specific response when pathogens pentrate first line of defence

includes:
Complement system
Transferrins
Phagocytes
NK cells
Inflammation
Cytokines (eg interferons)
Fever

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4
Q

Third line of defence

A

“Specific/adaptive immunity”

Activated by innate immune system, producing a response towards 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

What aRe antigens

A

A protein (hence specific 3D shape) with an identifiable genetic code
That can be recognised by leukocytes

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7
Q

2 main types of antigens

A
  1. Foreign (eg microbes, food, drugs)
  2. Self-antigens (present on cell membranes) - transmembrane proteins
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8
Q

What are antibodies

A

Proteins produced in response to a specific antigen
Combine with specific antigens reading identifiable code

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9
Q

Where are IgA found

A

Saliva, sweat, tears, breast milk, mucous secretions

Immunoglobulin - aka antibody - first layer of defence on surface

Stress compromised

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10
Q

How does the skin act as a first line of defence

A

Physical barrier with tightly packed epithelial cells
Outer epidermis consists of dead epithelial cells & sheds which remove microbes

Dermis contains accessory structures sebaceous & sweat glands which have immune functions

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11
Q

Immune function of sebaceous glands

A

Contains fatty acids which inhibit microbial growth as well as waterproofing the skin

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12
Q

mucous membranes as first line of defence

A

Digestive, respiratory & urogenital, conjunctiva

Contain IgA & lysozomes

Saliva, tears, mucous Wash away microbes & are antimicrobial

Mucous traps microbes & foreign bodies eg mucociliary escalator take down to stomach to be swallowed

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13
Q

What are transferrins

A

Iron-binding proteins in blood

Act to inhibit growth of certain bacteria, by reducing the amount of available iron

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14
Q

Why is excess iron problematic

A

Feeds bacteria if pathogens present
Increases favourable environment

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15
Q

What is the complement system

A

A defensive system of proteins that help to destroy microbes

made of over 30 proteins produced by the LIVER

Proteins Identified by a letter with a number eg C3
Proteins are inactive & only become active when split by enzymes into active fragments eg C3 > C3a + C3b

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16
Q

What is the classical pathway

A

Most common mechanism through which complement system is activated
Whereby antigen-antibody complexes are formed

When activated they act in a cascade -amplified

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17
Q

What is opsonisation

A

Where complement fragment C3b ‘coats’ a microbe causing phagocyte to attach

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18
Q

What complement fragments contribute to inflammation

A

C3a & C5a bind to mast cells & cause release histamine

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19
Q

What complement fragments contribute to cytolysis of a microbe

A

C5, 6,7,8,9
Join & create hole in cell, which causes it to take in fluid & ultimately bursts microbe

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20
Q

What are cytokines

A

Protein hormones that act as chemical messengers, stimulating or inhibiting immunity cell functions

Group of non-antibody proteins secreted by leukocytes

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21
Q

What are interleukins

A

Group of cytokines
Act as mediators between leukocytes

Released by macrophages

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22
Q

What are interferons

A

Grouped under cytokines
Produced by cells that are infected by a virus

Involved in anti-viral responses
Messenger tells surrounding uninfected cells to stop dividing & induce synthesis of anti-viral proteins that prevent viral replication

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23
Q

What are Tumour Necrosis Factor (TNF)

A

Grouped under cytokines

Promote accumulation of neutrophils & macrophages to cause cell death

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24
Q

Two main types of phagocytes

A
  1. Neutrophils
  2. Macrophages

Non-selective in targets
‘Antigen presenting cells’

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25
Q

Two types of macrophages

A

Aka Monocytes in blood, macrophages in tissue

Fixed = watch over specific tissues
Wandering = migrate to sites of infection & enlarge

Digests, excretes, sticks small amount onto its own cell membrane to then present to T-lymphocyte helper cells to learn specific antigens

‘Antigen presenting cells’

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26
Q

Two main antigen presenting cells

A

Macrophages & B-lymphocytes

Present to T-lymphocytes

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27
Q

Main types of fixed macrophages & where they are found

A

• histiocytes - connective tissue
• kupffer cells - liver & erythrocytosis
• alveolar macrophages -lungs
• microglia - nervous tissue
• langerhans cells - skin
• tissue macrophages - spleen, bone marrow & lymph nodes

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28
Q

What is a granuloma

A

Pathogens resistant to adherence in phagocytosis are instead surrounded by macrophages & immune cells to try & contain microbe
Eg tuberculosis

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29
Q

What are NK cells

A

Non-specific lymphocytes
Attack anything not recognised, including abnormal body cells
Bind to a target cell & release granules containing protein ‘perforin’

Present in blood, lymph nodes, spleen & bone marrow

30
Q

What is perforin

A

A protein released by NK granules when binding to a target cell
Perforin inserts into target cell membrane & creates a channel for tissue fluid to flow into the cell = cytolysis

31
Q

Main cardinal signs of inflammation

A

• redness
• heat
• pain
• swelling
• loss of function

32
Q

How do histamine & heparin promote inflammation

A

Cause vasodilation & increased permeability

Released by mast cells & basophils

33
Q

Leukotrienes as inflammatory mediator

A

Attract phagocytes & increase vessel permeability

Released by basophils & mast cells

34
Q

Kinins as inflammation mediators

A

Proteins that induce vasodilation & increase permeability. They also attract phagocytes & induce ‘pain’

35
Q

Prostaglandins as inflammatory mediators

A

Lipids released by damaged cells
Enhance effects of histamine & kinins (& so intensify pain)

36
Q

What does the cytokine interleukin-1 increase

A

A hormone protein that enters the blood & resets hypothalamus thermostat
Increases body temp/induces a fever

37
Q

Positives of elevated body temp

A
  • makes interferons more effective
  • inhibits growth of some microbes
  • speeds up reactions that aid repair

When reaching beyond 39 degrees becomes dangerous

38
Q

Leukocytes are either

A

Granular or agranular

39
Q

Most abundant leukocyte

A

Neutrophils 60%
Phagocytic cell
Release lysozomes that digest

40
Q

What cells release histamine & heparin & roles

A

Basophils & mast cells

Histamine = vasodilation/increase permeability
Heparin = anticoagulant
Involved in inflammation - easy flow to prevent stagnation

Express receptors for IgE & hence involved in allergies & hypersensitivity

41
Q

Main leukocyte involved in asthma

A

Eosinophils

Also destroy parastitic worms via phagocytosis (less efficient cell)

42
Q

Main antigen presenting cells

A

Macrophages

Also b lymphocytes

43
Q

What mediates the connection between ‘innate’ immune system & the ‘adaptive’

A

Cytokines & antigen presentation

T & B lymphocytes are usually at rest unless activated for specific antigens

44
Q

What is the MHC

A

Major Histocompatibility Complex

Group of cell surface proteins that are required for recognising self-antigens vs non-self

Formed of four polypeptide chains & display a protein produced by the cell (‘self’) on its binding groove

Two types
MHC-I
MHC-II

45
Q

Class I MHC role

A

Located on all body cells except erythrocytes
Cell produces its own proteins that combine with MHC-I & are displayed on the cell membrane indicating whether ‘self-antigen’
If damaged/abnormal this shows in the proteins produced

Allows leukocytes to differentiate between healthy body cells from abnormal/infected

46
Q

Class II MHC role

A

Located only on membrane of ‘antigen presenting cells’
Eg B-lymphocytes & macrophages

Displays the foreign antigen on its binding groove after ingestion to then present to T helper cells

47
Q

What involved in cell-mediated immunity

A

T-cells / T-lymphocytes

Each have a unique T-cell receptor
CD4 receptor
Produced in bone marrow but mature in thymus

48
Q

What involved in antibody-mediated immunity

A

B-cells / B-lymphocytes

49
Q

CD4 cells

A

CD4 protein present on surface

T-helper cells & macrophages

50
Q

CD8 cells

A

Cytotoxic T-cells

51
Q

What traits are T-cells tested for in the thymus

A
  1. Ability to recognise self-antigens
  2. Not react to self-antigens “self tolerance” - loss leads to autoimmunity

Tested against thymus epithelial cells
Only 1-5% make through the process

B-cells undergo similar screening process in bone marrow

52
Q

Role of interleukin 2 in antigen presentation

A

When antigen fragment binds with T helper cell it secretes the cytokine interleukin2

This causes T-lymphocyte proliferation & stimulates “clonal selection” of B-lymphocytes
This creates the active attack as well as immune memory

53
Q

What does cell mediated clonal selection produce

A
  1. Cytotoxic T-lymphocytes - protein digests via perforin & granzymes
  2. Memory T-lymphocytes
  3. Helper T-lymphocytes - release cytokines increasing immune cell activity
    Or suppresses when threat removed
54
Q

Role of regulatory T-cells

A

De-activate immune cells when response no longer required
Maintining immune system homeostasis & tolerance to self-antigens

55
Q

Why lock and key analogy for antibodies

A

Because they only bind specifically with the antigen that stimulated their production

“Antibody-antigen complexes” formed

56
Q

What ways can antibodies inactivate antigens

A
  1. Neutralising
  2. Immobilising - binding
  3. Agglutination & precipitating - both binding sites can cause clumping
  4. Activating complement cascade
  5. Enhance phagocytosis
57
Q

Concept of a vaccine

A

Immunological memory is the basis

Contain weakened, whole or partially dead portions of microbes - are immunogenic but not supposed to be pathogenic!

B & T cells activated can take several day

58
Q

Naturally acquired active immunity

A

Natural exposure to a disease

59
Q

Naturally acquired passive immunity

A

Transfer of IgG antibodies across the placenta from mother to child

Transfer of IgA from mother to child via breast milk

60
Q

Artificially acquired active immunity

A

Vaccination
Encourages bodies immune process

61
Q

Artificially acquired passive immunity

A

Injection with immunoglobulins eg anti-venom for snake bite

Immunity without body doing anything as remedy given

62
Q

Hypersensitivity means

A

An excessive immune response produced by normal immune system

63
Q

Hypersensitivity type I, II, III are mediated by

A

Antibody-mediated

64
Q

Hypersensitivity type IIII mediated by

A

Cell-mediated

T-cell aka cytotoxic

65
Q

What is type 1 hypersensitivity

A

Aka allergy

IgE antibody mediated (produced by plasma cells) that bind to mast cells causing degranulation

Immediate onset/rapid

Reactions eg hay fever, eczma, irritant contact dermatitis or serious reaction eg anaphylaxis & shock

66
Q

What is type 2 hypersensitivity

A

As seen in blood transfusions & haemolytic disease of newborn

IgG antibody mediated as can cross placenta
Bind to antigens on cell surface activating complement system

Rapid onset

67
Q

What is type 3 hypersensitivity

A

As seens in glomerulonephritis, RA & SLE (lupus)

Antibody-antigen complexes are formed and deposit in capillaries, skin, kidneys, joints which activates complement system triggering immune response eg inflammation

IgG, IgM, IgA mediated
Onset 4-8 hours

68
Q

What is type 4 hypersensitivity

A

Involved in skin graft rejection, allergen contact dermatitis & MS

Cell-mediated, over reaction of T-lymphocyte cells to an antigen
Large number of CD8 (cytotoxic) & cytokines released, damagining normal tissues

Delayed type, 48-72 hours

69
Q

What is anaphylactic shock

A

Severe, systemic allergic response within 5-10 mins of antigen exposure

IgE antibodies activate mast cells & basophils causing degranulation & histamine release

Bronchoconstriction, vasodilation & oedema of tissue
Danger because can occlude airways

Epinephrine treatment aka adrenaline - Epipen reverses histamine

70
Q

Structure of an antibody

A

Y shaped made up of 4 polypeptide chains
Containing a variable region & a constant region & 2 binding grooves

71
Q

What does antibody mediated clonal selection produce

A

Antigen binds to B cell where it is broken down and then expressed on the MHC-II
Helper T cells recognise the antigen complex on B membrane & release interleukin 2 which triggers B-cell clonal selection

Plasma cells (secrete antibodies) & Memory B cells are produced

Biomed2 (9 decks)

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