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3. Week 2 - General Pathological Mechanisms > Cells of the immune system > Flashcards

Cells of the immune system Flashcards

1
Q

What are the soluble factors of the innate immune system?

A
  • antibacterial

- complement system

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2
Q

What are the cellular factors of the innate immune system?

A
  • scavenger phagocytes
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3
Q

Name two examples of antibacterial factors

A
  • lysozymes

- lactoferrin

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4
Q

What is lysozyme and what does it do?

A
  • enzyme present at mucosal surfaces

- active in breaking down the gram positive cell wall

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5
Q

What is lactoferrin and what does it do?

A
  • protein found at mucosal surfaces

- chelates iron and reduces amount available in GI/respiratory tract, therefore inhibiting the growth of bacteria

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6
Q

What is complement

A

soluble factor of the immune system that can be present on mucosal surfaces but is very active in blood

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7
Q

What is the complement cascade?

A

enzymatic cascade with three ways of activation, culminating in a common activation pathway and resulting in different effects

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8
Q

Describe the classical pathway

A

Part of the complement cascade

The antibody-antigen complex creates a conformational change in the Fc region, allowing complement binding and activation

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9
Q

Describe the alternative pathway

A

Part of the complement cascade

Complement activated directly on pathogen surface

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10
Q

What are the key responses of the complement system?

A
  1. capable of killing bacteria by itself
  2. can opsonise pathogens to flag them for removal
  3. recruits inflammatory cells to the area
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11
Q

How does complement lead to the destruction of pathogens?

A

In the late steps of complement cascade, complement proteins form membrane attack complex, allowing them to ‘punch’ holes in the bacterial membrane causing lysis.

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12
Q

What are the scavenger phagocytes?

A
  1. macrophages (present in tissues normally)

2. neutrophils (enter tissue when inflammation present)

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13
Q

What bacteria can survive within macrophages for years?

A

mycobacterium tuberculosis

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14
Q

What are macrophages?

A

White blood cell derived from blood monocytes

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15
Q

What are the functions of macrophages

A
  • phagocytosis
  • antigen presentation
  • cytokine production
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16
Q

Describe the role of macrophages as an APC

A

processes engulfed particles, travels to draining lymph nodes and presents to T cells in MHC class II

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17
Q

What cytokines do macrophages produce?

A 
Inflammatory = TNF alpha
Regulatory = IL10
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18
Q

What are pattern recognition receptors?

A

E.g. Toll-like receptors

recognise molecules found commonly in micro-organisms
able to recognise extracellular and intracellular threats

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19
Q

What are neutrophils

A

First cell to respond to infection through the innate immune system due to chemotaxis

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20
Q

What are the roles of neutrophils?

A
  • phagocytic
  • degranulate
  • die locally
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21
Q

How do neutrophils migrate towards areas of infection

A

Neutrophils migrate towards bacterial products (e.g. LPS), chemokines and ‘danger signals’ (e.g. complement components)

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22
Q

How do neutrophils phagocytose pathogens?

A

using proteases, reactive oxygen species, lysozymes, etc.

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23
Q

What is the purpose of neutrophil degranulation?

A

Releases toxic granules extracellularly.

  • helps destroy pathogens
  • releases long strands of DNA to help tangle and trap the pathogens to further expose them to chemicals
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24
Q

What is the result of neutrophils dieing at the site of infection?

A

produces characteristic pus

25
Q

What is the main role of eosinophils

A

respond to parasites and have a role in allergy

26
Q

What substances are released from eosinophils on degranulation?

A
  • major basic protein
  • eosinophil cationic protein
  • eosinophil peroxidase

released onto surface of parasite

27
Q

What is the main role of basophils?

A

Mast cells

  • found at mucosal sites as a ‘guard’
  • important role in allergy
28
Q

Describe degranulation of mast cells

A

reapid release of pre-formed granules containing cytokines and mediators, e.g. histamine

29
Q

What cell links the innate and adaptive immune systems?

A

dendritic cell

30
Q

What is the role of the dendritic cell?

A

sits in tissue and projections sample the environment for signals to activate the immune response

31
Q

What are the processes dendritic cells are involved in?

A
  • phagocytosis
  • migration
  • antigen presenting
32
Q

Describe the role of dendritic cells in antigen presenting

A

Present to CD4 T cells and can initiate an adaptive immune response

33
Q

What are the main subdivisions of the adaptive immune response

A
  • humoral

- cellular

34
Q

What mediates the humoral immune response?

A
  • B cells
35
Q

What mediates the cellular immune response?

A
  • CD4 T cells

- CD8 T cells

36
Q

What is the role of CD4 T cells?

A

facilitate the immune response without partcipating in killing

37
Q

What is the role of CD8 T cells?

A

cytotoxic T cells, which are directly involved in killing cells

38
Q

What are the main functions of antibodies?

A
  • opsonisation for phagocytosis
  • activation of complement for lysis
  • neutralising toxins and pathogen binding sites
39
Q

What are the main antibody isotypes?

A
  • IgM
  • IgG
  • IgA
  • IgE
40
Q

What are the features of IgM

A

main antibody of primary immune response

  • low affinity
  • activates complement
41
Q

What are the features of IgG?

A

Main antibody of the secondary immune response

  • Higher affinity
  • Activates complement
  • binds Fc receptor on phagocytes
  • crosses placenta
42
Q

What are the features of IgA?

A

present in secretions and lines epithelial surfaces

neutralises by blocking binding of pathogens

43
Q

What are the features of IgE?

A

high affinity binding to mast cells through Fc receptor

- role in allergy

44
Q

What stimulates B cell activation?

A

Presentation of an antigen via APC and the addition of helper T cell or other stimuli

45
Q

What step occurs once a B cell is activated?

A

Clonal expansion

46
Q

What are the ways in which a B cell can differentiate?

A
  • Develop into plasma cells
  • undergo istype switching
  • generate memory B cells
47
Q

What is the T cell receptor?

A

Multi-protein receptor on surface of T cells that only recognises an antigen if it is bound to an MHC molecule
- only recognises short peptide lengths

48
Q

What is the ‘second signal’

A

Activation of lymphocytes requires both the present of ann antigen and the presence of a danger signal’.

Without second signal, the cell will become anergic

49
Q

Describe MHC class 1

A
  • presents to CD 8 T cells
  • found on all nucleated cells
  • Presents intracellular antigen (allows recognition of viral infected or cancer cells)
50
Q

Describe MHC class 2

A
  • presents to CD4 T cells
  • presents extra-cellular derived antigen (phagocytosed)
  • found on antigen presenting cells (DC’s, macrophages, B cells)
51
Q

What are the main groups of specialist CD4 cells?

A
  • Th1
  • Th2
  • Th17
52
Q

What is the role of Th1?

A

predominantly secretes interferon gamma and are though to be involved in intracellular immunity

53
Q

What is the role of Th2?

A

predominantly produces IL4 and are though to be responsible for antibody mediated responses

54
Q

What is the role of Th17?

A

produces IL17, which are important at the mucosal surface

55
Q

What are the main areas of note in the lymph node?

A
  • primary follicle
  • paracortical area
  • medullary cords
56
Q

What process occurs in the primary follicle?

A

inactive B cell sampling

57
Q

What process occurs in the paracortical area?

A

T cell sampling

58
Q

What process occurs in the medullary cords?

A

Macrophages and plasma cells are leaving the lymph node

3. Week 2 - General Pathological Mechanisms (12 decks)

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