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Principles Revision Points > Immunology > Flashcards

Immunology Flashcards

1
Q

What happens when the immune system goes wrong?

A 
Recurrent infections
Allergy
Autoimmune disease
Cancer
Transplant rejection
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2
Q

What are the skin’s constitutive barriers to infection?

A

Physical barrier
Physiological factors - low pH 5.5, low oxygen tension
Sebaceous glands - secrete hydrophobic oils, lysozyme, ammonia, antimicrobial proteins

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3
Q

What are the constitutive barriers to infection of mucous?

A

Physical barrier
Secretory IgA
Contains enzymes - lysozyme, defensins, antimicrobial peptides, lactoferrin
Cilia - trap pathogens and contribute to removal of mucous

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4
Q

What are the constitutive barriers of infection of commensal bacteria?

A 
Competition for essential nutrients
Reduction of pH or large bowel
Production of bactericidins
Synthesis of vitamins
Production of anti-microbial short chain fatty acids
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5
Q

What are the key features of the immune system?

A

Specifically identify and respond to ‘non-self’
Modify response to real with different pathogens
Promote tissue repair and healing
Immunological Memory

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6
Q

What are cytokines?
What do they do?
Give examples

A

Collection of small proteins and peptides, produced in response to infection, inflammation and tissue damage
Modulate behaviour of cells
Interferons, TNF alpha, chemokines, interleukins

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7
Q

What are natural killer cells?What are their functions?

A

Large granular lymphocytes
Kill tumour cells and virally infected cells
Kill antibody-bound cells and pathogens

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8
Q

What are the functions of B lymphocytes?

A

Production and secretion of antibodies

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9
Q

What are the two types of T lymphocytes?

What are their functions?

A

Helper T cells (CD4+) - key regulators of the immune system

Cytotoxic T cells (CD8+) - kill virally infected body cells

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10
Q

What are mast cells, basophils and eosinophils?
What are their functions?
Where are they located?

A

Highly granular cells which release chemicals eg histamine and cytokines, causing acute inflammation
Key role in mediating allergic response
Mast cells - in tissues and mucosal surfaces
Basophils and eosinophils - circulate in blood, recruited to sites of infection by inflammatory signals

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11
Q

What is the complement system?

What is its’ function?

A

Family of approximately 30 proteins, produced in the liver and circulate in blood
Enter infected/inflamed tissue where they become activated
Play a critical role in promoting inflammation and defence against bacterial species

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12
Q

What are monocytes, macrophages and neutrophils?

What are their functions?

A

Phagocytic ‘eating’ cells - ingest and kill bacteria and fungi
Clear debris from the body
Sources of cytokines which regulate acute inflammation

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13
Q

What is the function of dendritic cells?

A

Antigen presentation to T cells

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14
Q

Describe the main differences between innate and adaptive immune response

A

Innate - rapid, Adaptive - slow response

Innate - same generic response to pathogens, adaptive - response is unique to each individual pathogen

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15
Q

What are the two main methods of cells communicating with each other?

A 
Direct contact (receptor to ligand interactions)
Indirect (via release of cytokines)
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16
Q

How do innate immune cells recognise pathogens?

A

Pathogen associated molecular patterns (PAMPS) on ‘non-self’ molecules and pattern-recognition receptors (PPRs) on innate cells

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17
Q

What are the 3 main cells involved in the innate immune response?

A

Macrophages
Mast cells
NK cells

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18
Q

How do macrophages kill pathogens?

A

Phagocytosis

Bind with lysosomes which contain acid and lysosomal hydrolases

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19
Q

Some pathogens can evade macrophage killing. How is this overcome?

A

Macrophage activation is enhanced by pro-inflammatory cytokines such as INF gamma
This causes:
Increased production of toxic reactive oxygen and nitrogen species (ROS and RON)
Increased antigen presentation capability of macrophages

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20
Q

What two processes do mast cells undergo during an immune response?

A

Degranulation - release of pre-formed proinflammatory mediators
Gene expression - production of new proinflammatory mediators

21
Q

What is C Reactive Protein?

What does it do?

A

A major acute phase protein used as a marker for inflammation
Enhances phagocytosis and complement system activation

22
Q

What changes occur in blood vessels in acute inflammation?

A

Increase in vascular permeability
Vasodilation and increased blood flow
Endothelial cell activation - expression of selectins (receptors) and ICAM/VCAM-1 (ligands)
Transendothelial migration and chemotaxis of neutrophils (follow the chemokine gradient)

23
Q

What are the specific functions of neutrophils?

A

Kill extracellular pathogens

Produce pro-inflammatory cytokines

24
Q

What are the two mechanisms of neutrophil killing via phagocytosis?

A

Anti-microbial proteins (granules filled with acid, antimicrobial peptides, enzymes to digest the pathogen)
NADPH oxidase-dependent mechanisms (production of ROS)

25
Q

What methods, other than phagocytosis, are there of neutrophil killing?

A

Degranulation - release of anti-bacterial proteins into the extracellular space
NETs (Neutrophil extracellular traps - immobilise pathogens and facilitates phagocytosis

26
Q

What are the 4 functions of complement?

A

Pathogen killing
Pathogen opsonisation
Leukocyte recruitment and inflammation
Removal of immune-complexes

27
Q

What are the 3 methods of activation of complement?

A

Classical Pathway
Mannose-binding Lectin Pathway
Alternative Pathway

28
Q

What is Mannose-Binding Lectin, and how is it involved in complement activation?

A

A protein produced by the liver as part of the acute phase response
Catalyses the breakdown of C3 to C3b and C3a

29
Q

What is the alternative pathway of complement activation?

A

C3 spontaneously breaks down to C3a and C3b

C3b then causes an amplification loop if bound to a bacterium to cause further breakdown of C3

30
Q

What does C3b do?

A

Activates an amplification loop in the alternative pathway
Causes breakdown of C5 to C5a and C5b, C5b then forms a membrane attack complex
Opsonises pathogens

31
Q

What do C3a and C5a do?

A

They are anaphylatoxins, and promote inflammation

Act directly on blood vessels and on mast cells to cause release of pro-inflammatory mediators and chemokines

32
Q

Where are T cells and B cells produced?

Where are they activated?

A

Bone marrow

Activated in secondary lymphoid tissues when they meet an antigen

33
Q

What are antibodies composed of?

A

Two heavy Ig and two light Ig chains

34
Q

What happens at hypervariable regions of Ig chains?

A

Antigen binding

35
Q

How are different Ig chains produced?

A

Random rearrangement of gene segments in individual developing B cells

36
Q

How are B cells attracted to lymph nodes?

A

Migration of inflammatory mediators and dendritic cells

37
Q

What type of cells ‘trap’ opsonised antigens in lymph nodes?

A

Stromal cells

38
Q

What happens to a B cell once activated?

A

Entry into cell cycle and mitosis causing clonal expansion

Differentiation into plasma cells which produce antibodies, or memory cells

39
Q

What component of T cells recognises ‘non-self’ proteins?

A

MHC proteins

40
Q

Where do B cells differentiate?

A

Germinal centres

41
Q

What are the 5 classes of antibody?

A

IgG, IgD, IgA, IgE, IgM

42
Q

Describe features of IgM

A

Membrane bound monomer - B cell antigen receptor, causing B cell activation
First Ig type produced during an immune response
Present in plasma as a pentamer, causing agglutination and complement system activation

43
Q

What is agglutination?

A

When antibodies cross-link multiple antigens producing clumps of antigens
Mediated by IgM and IgG

44
Q

Describe features of IgG

A 
Most abundant antibody
Agglutination
Complement system activation
Foetal immune protection
Neutralisation
Opsonisation
NK cell activation
45
Q

Describe features of IgD

A

In membrane bound form serves as B cell antigen receptor, causing B cell activation

46
Q

Describe features of IgA

A

Second most abundant Ig type
Monomeric form is present in serum
Dimeric form is present in secretory fluids, providing neonatal defence and neutralisation

47
Q

Describe features of IgE

A

Trigger allergic responses by causing mast cell and basophil degranulation

48
Q

What do Th1 cells do?

A

‘Help’ macrophages, causing hyperactivation

49
Q

Which type of antibody is produced rapidly during the secondary immune response?

A

IgG

Principles Revision Points (11 decks)

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