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VMS 2009 > Innate immunity > Flashcards

Innate immunity Flashcards

1
Q

What are some examples of chemical barriers to infection?

A
  • Acid in the stomach
  • Mucus on the surface
  • antimicrobial properties e.g defensins which are secreted at the epithelial surface
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2
Q

What is the function of the innate barriers of infection

A

To prevent pathogens from gaining access to the deep tissues

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3
Q

What do epithelial layers produce?

A

They produce protective substances
* acidic pH
* enzymes and binding proteins
* antimicrobial peptides

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4
Q

What are sentinel cells?

A

Resident tissue cells that detect invasion by recognising DAMPS and PAMPS
they can then send signals to initiate a response to
* dendritic cells
* Macrophages
* Mast Cells
*

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5
Q

What kind of cells develop from myeloid progenitor cells?

A
  • Red blood cells
  • Monocytes
  • Megakaryocytes
  • Granulocytes
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6
Q

What kidn of cells develop from lymphoid progenitor cells

A
  • T cells
  • B cells
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7
Q

What is the precurser to macrophages and dendritic cells?

A

Monocytes

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8
Q

What is the function of dendritic cells?

A

Important bridge between innate and adaptive immunity
can act as APC’s

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9
Q

What kind of cells do NK cells kill?

A

any virus infected or abnormal cell that fails to express MHC Class I molecules

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10
Q

What kind of cells are MHC I molecules usually present on?

A

all nucleated cells of the body

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11
Q

What do MHC class I receptors do when they bind to NK cells?

A

switch off their ‘killing abilities’

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12
Q

What is the definition of phagocytosis?

A

engulfment and internalisation of materials such as microbes for their clearance and destruction

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13
Q

What are the two different receptors that are found on phagocytes (recognise microbes)

A
  • Pattern recognition receptors- bind to the LPS of bacteria
  • Opsonin receptors, e.g immunoglobulin FC receptors- bind to iG + AG
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14
Q

What is the definition of the complement system?

A

A group of serum proteins circulating in inactive form

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15
Q

What systems activate the complement system?

A

Both the adaptive (classical pathway) and the innate immune system ( alternative pathway)

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16
Q

What are the possible outcomes after the complement system is activated?

A
  • Targets cell lysis
  • Chemotaxis
  • Opsonisation to enhance phagocytosis
17
Q

What are the three activation pathways that are part of the complement system?

A
  • Classical
  • Lectin
  • Alternative
18
Q

What is the classical activation pathway

A

requires the interaction of an antibody with a specific antigen

19
Q

What is the lectin activation pathway?

A

PAMPS recognition by lectin receptors

20
Q

What is the alternative activation pathway?

A

activation of the complement via the microbe itself

21
Q

What is the function of cytokines?

A
  • coordinate an effective immune response
  • Moderate the communication between lymphocytes, inflammatory cells
    and haematopoietic cells.
  • additional roles separate from the immune system in developmental
    processes such as
  • cell differentiation
  • directed migration.

Influencing both innate and adaptive immune responses

22
Q

What are some of the different families of cytokines?

A
  • Pro-inflammatory cytokines
  • Chemokines
  • Inteferons
23
Q

Where do defensins sit?

A

They sit in the lipid bilayer

24
Q

What two cells are examples of monocytes?

A

Macrophages and dendritic cells

25
Q

How many populations of innate lymphoid cells are there?

A

at least four
* ILC1- found in large numbers in the intestinal wall
* ILC2- scattered throughout the body and secrete cytokines
* ILC3- act like TH17 cells and promote inflammation by releasing TH17
* ILC4 natural killer cells

26
Q

How do defensins work?

A

They can directly kill or inhibit the growth of microorganisms

27
Q

What are the two phagocytic cells?

A

Neutrophils and Macrophages

28
Q

What are the innate lymphoid cells?

A
  • Cytokine secreting ILC’s
  • Cytotoxic ILC-NK cells
29
Q

How do the leukocytes get where they are required?

A
  1. Macrophages produces cytokines such as TNF-alpha and IL-1
  2. TNF-alpha, IL1 and other chemokines activate selectins
  3. The force of blood flow causes leukocytes to roll
  4. Chemokines produced in the surrounding tissues bind to the rolling leukocytes in a high affinity state
  5. Leukocytes can crawl to junctions and migrate through the wall (diapedesis)
30
Q

What are the functions of the natural killer cells?

A
  • They can kill virus-infected or other ‘abnormal’ cells that fail to express MHC class I molecules
  • If MHC I binds to a natural killer cell it ‘switches off’ the killing abilities
31
Q

What happens when certain viruses and tumours ‘down regulate’ the expression of the MHC class I molecules?

A

The natural killer cells bind to the virus-infected target cells, inject them with proteins to induce cell death and thus eliminate the virus-infected cells

32
Q

Give some examples of antimicrobial phagocytic mechanisms

A
  • Toxic Nitrogen oxides- NO
  • Enzymes- Lysozyme (digests the cell wall of gram-positve bacteria)
  • Antimicrobial peptides- Cathelicidin in macrophages, defensins in neutrophils
33
Q

How does the classical pathway begin?

A

Antibodies binding to antigens, Cleavage of C1 causes a cascade of other proteins becioming activated

34
Q

How does the alternative pathway begin?

A

With the spontaneous hydrolysis of C3

35
Q

What are pro-inflammatory cytokines?

A

IL1, IL6, TNF
Secreted by sentinel cells in response to DAMPS and PAMPS
Causes fever, lethargy, loss of appetite

36
Q

What kind of cells produce interferons?

A
  • Produced by virally infected cells, within 24 hours of some infections
37
Q

What kind of cells can produce chemokines?

A

Sentinel Cells

VMS 2009 (45 decks)

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