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MB4030 > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

Innate Immunity

A
  • 1st line of defence
  • more general
  • triggers acute inflammation response
  • phagocytosis by NFs, macrophages, DCs
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2
Q

Cells that initiate acute inflammation response?

A
  • NFs
  • macrophages
  • DCs

=> produce cytokines and IFNs

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3
Q

Adaptive Immunity

A
  • more specific
  • tailored to pathogen
  • long-lasting or protective immunity to host
  • found only in vertebrates
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4
Q

Cells connecting innate and adaptive immune system

A

DCs and macrophages -> act as APCs

  • present processed antigens from killed pathogens to adaptive/specific immune system to T-cells
    (Th and T cytotoxic)
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5
Q

Innate vs Adaptive

A

Innate:
- generic receptors (TLRs)
- fast (hours/days)
- no amplification
- short duration
- no self discrimination

Adaptive:
- highly specific (TCRs and BCRs)
- slow (days/wks)
- amplification
- long duration (immunological memory)
- has self discrimination from self antigens and non self

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6
Q

Antigen specific receptors in jawed vertebrates

A

Adaptive:
- BCRs and TCRs
- Jawless: variable lymphocyte receptors (VLRs)

Innate:
- PRRs (i.e. TLRs)

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7
Q

Primary Lymphoid Organs

A
  • bone marrow (stem cells give rise to all immune cells except T cells)
  • thymus (produces T-cells)
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8
Q

Secondary Lymphoid Cells

A

Lymph nodes
Spleen

(non-circulating immune cells)

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9
Q

Site of haemopoiesis

A

Primary lymphoid organs (bone marrow, thymus)

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10
Q

Hematopoiesis

A

The development of major immune cell lineages

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11
Q

What cells develop in bone marrow?

A

All except T lymphocytes (occur in thymus)

At birth: all bones of the skeleton
By puberty: sternum, vertebrate, iliac bones and ribs

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12
Q

Types of Adaptive Immunity

A

1) Humoral
2) Cell-mediated

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13
Q

Humoral Immunity

A

B lymphocytes -> secrete Abs -> eliminate extracellular microbes

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14
Q

Cell-mediated immunity

A

Helper T cells (CD4+) - cytokines
Cytotoxic T cells (CD8+) - directly kill
(extracellular pathogens)

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15
Q

Immunity to bacteria and fungi

A
  • mainly involves phagocytosis and Abs
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16
Q

Determinants of the defence mechanism against bacteria

A
  • gram +ve - strep pneumonia (lungs)
  • gram -ve h.pylori (gastric ulcers) (TB)
  • gram +ve -> cell wall is 90% peptidoglycan -> susceptible to lysozyme degradation
  • gram -ve -> susceptible to lysis by complement
17
Q

How are the majority of bacteria killed?

A
  • phagocytosis
    -ab mediated opsonization (binding of Fe by lactoferrin)
18
Q

How can phagocytes detect the presence of bacteria and viruses?

A

PRRs on their surface

19
Q

What do PRRs detect?

A

PAMPS (danger signals)
e.g. TLRs (TLR4 detects LPS (endotoxin))

20
Q

How do macrophages and DCs recognise bacteria, fungi and viruses?

A
  • PRRs (TLRs)
  • mannosyl-fucose receptors -> bind sugars on surface of microbes
  • CD14 receptors -> LPS binding protein
  • Fc receptors -> bind Abs to pathogen
  • Complement receptors (CR1/CD35) -> bind complement coated microbes
21
Q

Role of Ab

A
  • direct ab neutralization of toxins
  • secretory IgA (sIgA) for protection of mucosal surfaces - sIga dimers secreted onto intestinal lumen surface
  • opsonisation of bacteria with ab - enhances phagocytosis (NFs and macrophages)
22
Q

What immune cells express PRRs?

A

All do but main source is innate

23
Q

TLRs in endosome

A

TLR3: dsRNA & ssRNA viruses
TLR7: ssRNA viruses
TLR9: CpG dsDNA

-> mainly found on APCs

24
Q

RNA Viruses TLRs

A
  • TLR3,7,9
  • RLRs (RIG-1 like & MDA5)
  • NLRs (NLRP1,2,3)
25
Q

DNA Viruses TLRs

A
  • TLR9 (CpG DNA)
  • PKR (protein kinase receptor)
26
Q

What happens once PRRs are recognised?

A
  • production of inflamm cytokines and chemokines
  • enhances immune cell migration and function
  • IFNs released (IFN-a, IFN-b) - antivirals
27
Q

How does the immune system recognise viruses?

A

cytosolic innate receptors
(expressed in all cell types)

28
Q

Virus gene products which inhibit cytosolic innate immune sensor

A

RLRs and NLRs
(sense viral genome ss or ds and products of virus gene expression)

29
Q

Subclass of cytokines

A

Interleukins
- mediate interactions between leukocytes
- bridge innate and adaptive

30
Q

How are ILs released?

A

After PAMP recognition by PRRs

Also released from infected cells - bind to nearby uninfected cells - induce those to release cytokines -> cytokine burst

31
Q

IL example

A

IL-8

  • released by macrophages
  • attracts NFs to SOI
32
Q

Interferons

A

Cytokines produced early in a virus infection

  • one of the first lines of defence against viral infection (IFNa,b)
33
Q

What cells produce large amounts of Interferons?

A

DCs - particularly pDCs

34
Q

Function of IFNs

A
  • signals neighbouring uninfected cells to destroy RNA and reduce proteins synthesis
  • signals neighbouring infected cells to undergo apoptosis
  • activates immune cells (DCs, T-Cells, B-Cells)

-> develops within a few hours
-> lasts 1 to 2 days

35
Q

RNases

A

Destroys virus DNA or RNA

36
Q

Application of IFN

A

recombinant IFNa - treat hepatitis C virus infected patient

37
Q

Inflammation

A

immune systems response to infections and tissue injury

Characterised by:
- immune cell migration
-serum protein and cellular leakage into inflamm site (edema)

38
Q

5 symptoms of inflammation

A
  1. redness (rubor)
  2. heat (calor)
  3. pain (dalor)
  4. swelling (tumour)
  5. altered function

MB4030 (11 decks)

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