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IMS > Immunology > Flashcards

Immunology Flashcards

1
Q

What is the immune system?

A

A very complex group of many molecules, cells, tissues and organs that provide protection from microbes, tumour cells or foreign material

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2
Q

What is an antigen?

A

Any substance that when recognised by the immune system will trigger an immune response

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3
Q

Label this

A
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4
Q

What is an antibody?

A

A specific protein made in response to an antigen

Produced by B cells

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5
Q

What do neutrophils do?

A

They rapidly enter infected tissues in large numbers (first line and non-specific)
-release toxic chemicals
-release chemicals to attract other immune cells
-phagocytose organisms
-create extracellular traps using DNA

Especially useful in bacteria/ fungal infections
Form pus

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6
Q

What are basophils/mast cells?

A

Both release histamine (causes vasodilation)
This helps in the defense against multicellular parasites
Can cause tissue damage in allergy

Multicellular parasites = helminths

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7
Q

What are eosinophils?

A

Contain red granules containing toxic proteins and free radicals
These help in the defence against multicellular parasites
Can cause tissue damage in allergy

Multicellular parasites = helminths

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8
Q

What are dendritic cells?

A

Located in tissues that are common points for initial infection (skin/lungs/GI tract)
Main role is as an APC

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9
Q

What are monocytes/macrophages?

A

Role = phagocytosis/APC/Recruit other immune cells

Monocytes are found circuating in the blood
Macrophages are found in tissues

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10
Q

What are natural killer cells?

A

Release perforins and granzymes
Trigger apoptosis in infected host cells
Trigger apoptosis in cancerous cells

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11
Q

What are the key immunological sites?

A

Bone marrow
Thymus
Lymph nodes
Spleen

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12
Q

Label these immunological sites

A
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13
Q

Describe the role of the bone marrow as an immunological site?

A

Site of production of white/red blood cells and platelets
Also site of B cell maturation

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14
Q

Describe the role of the thymus as an immunological site?

A

Site of T cell maturation
Gland behind the sternum
Larger in children

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15
Q

Describe the role of lymph nodes as immunological sites?

A

Found throughout body (neck, armpit, groin)
Connected via channel of lymphatic vessels
Act as sieves to filter out any infection/cancer from lymph fluid
APCs in lymph fluid can meet many naive B and T cells in a lymph node

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16
Q

Describe the role of the spleen as an immunological site?

A

Made up of white and red pulp
White pulp acts like a big lymph node
Red pulp filters out old red blood cells

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17
Q

What is the difference between innate and adaptive immunity?

A
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18
Q

What are the physical barriers of innate immunity?

A

Intact skin & mucous membranes
Mucus and cilia
Tears and eyelashes
Sweat and body hair

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19
Q

What are the chemical mediators of innate immunity?

A

Lysozyme
Interferon
Complement

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20
Q

What immune cells are part of innate immunity?

A

Macrophages
Neutrophils
Natural killer cells

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21
Q

What are the two types of adaptive immunity?

A

Humoral (B-cell)
Cell mediated (T-cell)

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22
Q

What is the difference in passive and active immunity?

A

Passive - you receive antibodies somebody else has made (naturally or artificially)
Active - you make your own antibodies
Passive gives short term protection
Active gives long term immunity

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23
Q

What are the effectors of the complement cascade?

A

MAC (membrane attack complex)
Anaphylatoxins
Opsonisation (priming of pathogens for phagocytosis)
Neutrophils

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24
Q

What are naive B cells?

A

Circulating B cells which when activated, initiate the germinal centre response

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25
Q

What are Memory B cells?

A

Dormant B cells that arise from B cell differentiation and initiate a stronger more rapid antibody response

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26
Q

What are plasma cells?

A

Terminally differentiated B cells which contain abundant antibodies

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27
Q

What are cytotoxic T cells?

A

T cells which express CDB and recognise antigens associated with MHC class 1 molecules
They are capable of destroying virally infected or allogeneic cells

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28
Q

Describe the structure of a lymph node

A

Insert picture

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29
Q

What are the three steps of the innate immune system?

A
  1. Complement activation
  2. Phagocytosis by macrophages and neutrophils
  3. Natural Killer cells
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30
Q

What are the three activation pathways of the complement cascade?

A

Classical
Lectose or mannose-binding
Alternative

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31
Q

Please could you talk me through the steps of the classical pathway

A
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32
Q

What kind of protein are many of the complement factors?

A

Serine proteases

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33
Q

Please could you talk me through the steps of the lectin pathway

A

Mannose-binding lectin binds to mannose (sugar found on surface of pathogens)
MBL binds MASP 1 & 2 which activate C2 and C4
Rest of pathway identical to classical pathway

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34
Q

Please could you talk me through the steps of the alternative pathway

A

Low rate auto activation of C3
Auto-actiivated C3b binds factor B and properdin on pathogen surface which activates more C3 and activates C5

Rest of the pathway the same as classical (C6-9)

35
Q

Which peptides in the complement pathway are anaphylatoxins?

A

C3a, C4a, C5a

36
Q

What do anaphylatoxins do?

A

Trigger degranulation of endothelial cells, mast cells and phagocytes
Enhance vascular permeability
C3a and C5a are chemoattractants for neutrophils

37
Q

Explain the process of opsomisation by C3b

A

C3b binds pathogens
C3b is cleaved to iC3b
Macrophages have receptors for iC3b which facilitates phagocytosis

38
Q

What cells are involved in the cellular response?

A

Neutrophils
Monocytes
Natural Killer cells

39
Q

What immune cells are capable of phagocytosis?

A

Macrophages
Dendritic cells
Neutrophils

40
Q

What are the steps in phagocytosis?

A
  1. phagocyte sticks to microbe
  2. ingestion of microbe by phagocyte
  3. formation of phagosome
  4. fusion of phagosome with lysosome
  5. digestion of ingested microbe by enzymes
  6. formation of residual body containing indigestible material
  7. discharge of waste materials
41
Q

Where are macrophages located and what do they do?

A

Loacted in the skin, lungs, intestines
First defence against pathogens

42
Q

What are the three activation states of macrophages?

A

resting, primed, hyper-active

43
Q

What do resting macrophages do?

A
  • collect tissue debris
  • eliminates apoptotic cells
  • low major histocompatibility complex class 2 expression
44
Q

What do primed macrophages do?

A

Primed by interferon gamma produced by natural killer cells and helper t cells
Increased expression of MHC 2
Increasingly phagocytotic

45
Q

What do hyperactive macrophages do?

A
  • stimulated with things produced by gram negative bacteria
  • stop proliferating, become larger and very phagocytotic
  • produce cytokines
46
Q

Are neutrophils short or long lived?

A

Short (around 5 days)

47
Q

How do natural killer cells induce apoptosis of infected cells?

A

They release cytotoxic granules containing perforin and granzyme B (suicide enzyme)
Fas binds Fas ligand on target cell
Saves healthy host cells by recognising MHC-1

48
Q

What are Helper T cells?

A

T cells which express CD4 and recognise antigens associated with MHC class 2 molecules

49
Q

How are B cells activated?

A

Antigen binds to B cell receptors
B cells becomes APC
Th2 cell recognises APC
Clonal expansion leading to proliferation into plasma and memory b cells

50
Q

Explain the germinal centre response

A

B cells proliferate by clonal expansion in the lymph nodes in the “dark zone”
There is also class switching and hypermutation

51
Q

What is VDJ recombination?

A

A process that takes place during B cell development which allows them to generate a diverse range of receptors (on the variable section of an antibody)

52
Q

Whats the difference between IgG, IgM, IgA, IgD, IgE?

A

They are all different types of antibodies
IgG is the most abundant
IgM is the first antibody response made (doesn’t need T cells)
(others not very relevant)

53
Q

What is the difference in antibody production in the primary and secondary immune response?

A

Primary response - mostly IgM produced as quick but less specific
Secondary response - mostly IgG produced due to memory cells, highly specific and effective

54
Q

Which MHC class am I describing?
- found on all nucleated cells and platelets
- bound by CD8 on cytotoxic T cells
- displays peptide fragmentss of proteins from within the cell

A

MHC class 1

55
Q

Which MHC class am I describing?
- Found on B cells, macrophages, monocytes, antigen presenting cells and some T cells
- bound by CD4 molecules on helper T cells
- displays antigens derived from extracellular proteins whcih have been aquired through phagocytosis

A

MHC class 2

56
Q

What is the difference in structure of MHC class 1 and 2 molecules?

A

MHC class 1 is made of alpha chains 1,2,3 and beta 2 microglobulin
MHC class 2 is made of chains alpha 1 and beta 1

57
Q

Define the term tolerance

A

A specific immune non-reactivity against certain antigens

Clonal deletion - Naive B and T cells that have receptors to self antigens are destoryed before they finish maturing

58
Q

Define the term anergy

A

When the immune system is unable to do a normal immune response against a specific antigen

B and T cells become “frozen” and are unable to activate

59
Q

What is hypersensitivity?

A

Over-reaction of the immune response causing tissue damage

60
Q

What is the difference between allergy and autoimmunity?

A

Autoimmunity is hypersensitvity reactions agaisnt self antigens but allergy is against exogenous antigens

61
Q

What is an immunodeficiency?

A

Absent or defective immune response

62
Q

What is the mechanism of type I hypersensitivity?

A

Exposure to allergen
Allergen binds to IgE on mast cells
IgE cross linking
Triggers degranulation
Releases histamine, eosinophil/neutrophil chemotactic agent, proteases

63
Q

In type 1 hypersensitivity what is the effect of the release of histamine, eosinophil/neutrophil chemotactic agent and proteases?

A

Histamine - vasodilation
Eosinophil/neutrophil chemotactic agent - increased inflammatory cells
Proteases - tissue damage

64
Q

What are some examples of Type I hypersensitivity (IgE mediated) ?

A

Ezecma, asthma, hay fever, anaphylaxis

65
Q

What is the mechanism of type II sensitivity?

A

Antibodies from our own immune system (IgG or IgM) bind to target antigen on cell surface
Triggers one of 3 mechanisms
- cytotoxic T cell binds to antibody which releases granzymes and triggers apoptosis
- activates complement pathway
- antigen is a cell surface receptor so the antibody blocks the normal receptor altering the cell function

66
Q

What are some examples of Type II sensitivity?

A

Graves disease
Blood transfusion reactions

67
Q

What is the mechanism of Type III hypersensitivity?

A

Increased antibody production in response to antigen
Antibodies enter the blood and bind to soluble antigens
Immune complexes form
Immune complexes get lodged in the basement membrane of blood vessels
Activates complement cascade

68
Q

What are some examples of Type III sensitivity?

A

Lupus
Rheumatoid arthritis

69
Q

What is the mechanism of type IV (delayed) hypersensitivity?

A

Sensitisation
- exposure to antigen
- engulfed by APC
- antigen presented to naive CD4 T cells
- naive CD4 cell matures to a TH1 cell
Once sensitised
- Repeat exposure to antigen
- Antigen binds to TH1 cell
- cytokines releases
- macrophages activated
- cytotoxic t cells activated

70
Q

What are some examples of Type IV (delayed) hypersensitivity?

A

Coeliac disease
Type 1 diabetes

71
Q

Why do autoimmune diseases arise?

A

Due to type II/III/IV hypersensitivity reactions against self antigens

72
Q

What are the two types of tolerance and explain the difference

A

**Central **- in bone marrow/thymus when self lymphocye is maturing
Peripheral - if self lymphocyte escapes into circulation

73
Q

Is there a specific group where autoimmune diseases are more common?

A

Yes - younger women

74
Q

How are autoimmune diseases commonly treated?

A

With immunosupression often using steroids

75
Q

What are some common examples of autoimmune diseases?

A

Lupus
Type 1 diabetes mellitus
Graves disease

76
Q

What causes allergy?

A

Type I hypersensitivity reactions against certain exogenous antigens

77
Q

Which conditions make up the atopic triad?

A

Asthma
Eczema
Hay fever

78
Q

What are three examples of primary (genetic) immunodeficiency?

A

Di George syndrome
SCID (severe combined immune deficiency)
CVID (combined variable immune deficiency)

79
Q

What are three examples of secondary (acquired) immunodeficiency?

A

Malnutrition
Drugs
HIV/AIDS

80
Q

Why does HIV/AIDS mean you can acquire immunodeficiency?

A

HIV infects CD4 + T helper cells
Takes over T cell to enable viral replication
T cell function falls
Increased risk of opportunistic infections

81
Q

What different types of vaccines are there?

A

Administering…
- the whole microbe (inactivated/killed)
- part of the microbe
- genetic material of the microbe

82
Q

What classes of HLAs do we have to try get as similar as possible for organ transplantation?

A

A, B, DR

83
Q

What determines which HLAs we have?

A

Inherited from parents, three from mother and three from father
Expressed in a co-dominant manner
So we have 6 markers

IMS (10 decks)

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