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

Cells of the immune system Flashcards

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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?

Study These Flashcards
A

produces characteristic pus

25
What is the main role of eosinophils
respond to parasites and have a role in allergy
26
What substances are released from eosinophils on degranulation?
- major basic protein - eosinophil cationic protein - eosinophil peroxidase released onto surface of parasite
27
What is the main role of basophils?
Mast cells - found at mucosal sites as a 'guard' - important role in allergy
28
Describe degranulation of mast cells
reapid release of pre-formed granules containing cytokines and mediators, e.g. histamine
29
What cell links the innate and adaptive immune systems?
dendritic cell
30
What is the role of the dendritic cell?
sits in tissue and projections sample the environment for signals to activate the immune response
31
What are the processes dendritic cells are involved in?
- phagocytosis - migration - antigen presenting
32
Describe the role of dendritic cells in antigen presenting
Present to CD4 T cells and can initiate an adaptive immune response
33
What are the main subdivisions of the adaptive immune response
- humoral | - cellular
34
What mediates the humoral immune response?
- B cells
35
What mediates the cellular immune response?
- CD4 T cells | - CD8 T cells
36
What is the role of CD4 T cells?
facilitate the immune response without partcipating in killing
37
What is the role of CD8 T cells?
cytotoxic T cells, which are directly involved in killing cells
38
What are the main functions of antibodies?
- opsonisation for phagocytosis - activation of complement for lysis - neutralising toxins and pathogen binding sites
39
What are the main antibody isotypes?
- IgM - IgG - IgA - IgE
40
What are the features of IgM
main antibody of primary immune response - low affinity - activates complement
41
What are the features of IgG?
Main antibody of the secondary immune response - Higher affinity - Activates complement - binds Fc receptor on phagocytes - crosses placenta
42
What are the features of IgA?
present in secretions and lines epithelial surfaces | neutralises by blocking binding of pathogens
43
What are the features of IgE?
high affinity binding to mast cells through Fc receptor | - role in allergy
44
What stimulates B cell activation?
Presentation of an antigen via APC and the addition of helper T cell or other stimuli
45
What step occurs once a B cell is activated?
Clonal expansion
46
What are the ways in which a B cell can differentiate?
- Develop into plasma cells - undergo istype switching - generate memory B cells
47
What is the T cell receptor?
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
What is the 'second signal'
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
Describe MHC class 1
- presents to CD 8 T cells - found on all nucleated cells - Presents intracellular antigen (allows recognition of viral infected or cancer cells)
50
Describe MHC class 2
- presents to CD4 T cells - presents extra-cellular derived antigen (phagocytosed) - found on antigen presenting cells (DC's, macrophages, B cells)
51
What are the main groups of specialist CD4 cells?
- Th1 - Th2 - Th17
52
What is the role of Th1?
predominantly secretes interferon gamma and are though to be involved in intracellular immunity
53
What is the role of Th2?
predominantly produces IL4 and are though to be responsible for antibody mediated responses
54
What is the role of Th17?
produces IL17, which are important at the mucosal surface
55
What are the main areas of note in the lymph node?
- primary follicle - paracortical area - medullary cords
56
What process occurs in the primary follicle?
inactive B cell sampling
57
What process occurs in the paracortical area?
T cell sampling
58
What process occurs in the medullary cords?
Macrophages and plasma cells are leaving the lymph node

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

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