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PBL Week 3 > Innate immune response > Flashcards

Innate immune response Flashcards

1
Q

Signs & symptoms of inflammation?

A

Redness

Pain

Swelling

heat

Loss of function

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2
Q

What is function of immune system?

A

To eliminate pathogens & minimise damage they cause

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3
Q

How is the immune system tailored to the pathogen and location of infection?

A

Viruses &intracellular bacteria - cytoxic T cells.

Extracellular fungi, parasites & bacteria - detection of antigens by antibodies & destruction by phagocytes.

Large paracites - deposition of toxic substances or death by mast cells/eosinophils.

Immunoprivilaged areas - no immune response e.g. CNS, eyes, placenta.

Commensual bacteria - in the gut is tolerated.

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4
Q

Name the 3 levels of defence

A
  1. External defences
  2. Innate immune system
  3. Adaptive immune system

1& 2 make up the complementary cascade!

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5
Q

3 main differences between adaptive & innate immune response

A

Innate immune response is fast (occurs in mins) whereas adaptive takes several days

Innate has low specificity whereas the adaptive is highly specific.

innate immune response does not have memory function whereas memory cells are generated during the adaptive

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6
Q

List exterior defences of body?

A

Eyes- tears- contains chemical inhibiting bacterial growth

Nasal cavity- hair & muscus- trap micro-organism

Skin- barrier

Stomach- acid- kills organisms

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7
Q

What is innate immunity?

A

Born with- present from birth.

Non-specific- similar mechanism of action for all pathogens

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8
Q

What is adaptive immunity?

A

Immune response developed after birth

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9
Q

Define DAMPs

A

damage-associated molecular patterns– molecules that are released from damaged or necrotic host cells e.g. ATP, uric acid, heat-shock proteins.

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10
Q

Define PAMPs

A

Carbohydrate, polypeptide & nucleic acid ‘signatures’ that are expressed by viruses, bacteria & parasites, but differ from molecules on the host cell.

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11
Q

Name the tissues & organs involved in immune system?

A

Primary lymphoid organ- development & maturation of adaptive immune cells
- bine marrow- B cells
- Thymus gland- T cells

Secondary lymphoid organ- where matured lymphocytes meet pathogens
- spleen
- adenoids
- tonsils
- appendix
- lymph nodes
- MALT

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12
Q

Function of spleen?

A

Next to stomach behind left ribs

controls levels of RBC, WBC & platelets

Filters blood & removes old or damaged RBC

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13
Q

Function of adenoids?

A

small lumps of tissue at back of nose, above roof of mouth

Help trap pathogens that enter nose

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14
Q

Function of tonsils?

A

Help trap pathogens the enter mouth

Contain lymphocytes

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15
Q

Function of lymph nodes?

A

Filter pathogens that travel through lymphatic fluid & contain lymphocytes

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16
Q

Function of mucosa-associated lymphoid tissue (MALT)?

A

Initiates local Iga immune responses- passed on to lymph nodes

Found in submucosal layers of systems e.g. breast, eyes

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17
Q

What occurs in the lymph nodes?

A
  • Pathogens from infected tissue sites are picked up by dendritic cells & arrive at closest lymph node
  • Circulating B & T lymphocytes enter the node & congregate at specific regions (cortex/paracortex)
  • T or B cells are activated & proliferate if a match is found for the antigen.
  • Produce a large clone army that can go & find the pathogen in the body.
  • architecture size of lymph node changes to respond to the activation of the lymphocytes.
18
Q

What occurs at spleen & MALT?

A

Same thing as lymph nodes- dendritic cells try to find matching T or B cells

19
Q

Function of appendix?

A

projects from colon

stores good bacteria to root system after diarrhoea illness

20
Q

What is Haematopoiesis? Explain the process.

A
  1. All blood cells are derived from multipotent stem cells
  2. This stem cell divides into myeloid progenitor or lymphoid progenitor cells.
  3. Myeloid progenitors can form 3 cell types:
    - Megakaryote - becomes platelets.
    - Erythroblast - becomes red blood cells.
    - Myeloblast- become: white blood cells (leukocyte NOTE: this is different from a lymphocyte which are T or B cells).
  4. Monocytes - which form macrophages and dendritic cells.
    -Neutrophils
    • Basophils
    • Eosinophils

Occurs in bone marrow

21
Q

Name cells of innate immune response?

A

Nuetrophils

Mast cells

basophils

dendritic cell

eosinophils

macrophages

Natural killer cells

^all a type of white blood cell (leukocytes)

22
Q

Function of neutrophils?

A

Function:
- Phagocytes- engulfs & kills pathogen
- release of antimicrobial factors

Contains enzymes in their granules

Found in blood- highly mobile

Usually first cell to respond to infection
- recruited to site of infection by IL-8

Major component of pus

23
Q

Function of mast cells?

A

Reside in connective tissue & mucous membrane

Function:
- dilates blood vessels
- Involved in serious allergic reactions- induces inflammation by releasing histamine & heparin
- kill larger parasites that are to big to be phagocytose
1.Larger parasites are coated by IgE cells so recognised by IgE receptors on these cells.
2. Release histamine and proteases to kill the large parasite.
3. They are associated with allergies - release cytokines = inflammation.

Help link innate & adaptive immunity to fight pathogens- recruit macrophages & neutrophils

24
Q

Function of basophils

A

Travel from blood to tissue

Function:
- Fight parasitic infections- release histamine= inflammation
- role in blood clotting
- Granules contain heparin
- involved in allergic reactions
- Respond to pathogens tagged w/ IgG, IgE

25
Q

Function of dendritic cells?

A

Located in tissue that are in contact w/ external environment (skin)

Function:
- antigen presentation & phagocytosis.
- They migrate to the lymph nodes to find a matching T or B cell so they then activate the adaptive immune response

LINK INNATE & ADAPTIVE

26
Q

Function of eosinophils?

A

lobes contain toxins/ enzymes

kill bacteria & parasite

circulate in blood & migrate to tissue

27
Q

Function of macrophages?

A

migrate from blood to tissue spaces for invading pathogens

Function:
- Phagocytic cells- engulf & destroy bacteria through ROS
- antigen-presenting- for T cells of adaptive response
- release chemokines- attract other immune cells to site of infections

28
Q

Function of natural killer cells?

A

Identify intracellular infections e.g. viral infections & altered-self’ cells = important for identifying cancer.

Detect the lack of MHC class I on the cells’ surface.
- MHC class I is the self-peptide.
- An interaction w/ normal, intact MHC I molecules on healthy cells disables their killing sequence.
- If NK cells meet an infected cell, its cytoplasm secretes granules containing perforin.
- Granzymesare released too – a protease that digests cellular proteins &induces the target cell to undergo apoptosis

29
Q

How do cells of innate immunity respond to infection?

A
  1. Cells in the blood &lymph detect the specific PAMPs on the pathogen’s surface – act like red flag to the immune system.
  2. Macrophages, neutrophils and dendritic cells have pattern recognition receptors (PRRs) that recognise these PAMPs e.g. Toll-like receptors
  3. The binding of PRRs w/ PAMPs triggers the release of cytokines e.g. interferon- signal that a pathogen is present & needs to be destroyed.

NOTE: Interleukins are a subclass of cytokines that are involved in bridging the innate & active immune responses.

  1. Cytokines cause chemotaxis of neutrophils, macrophages & dendritic cells to the infected cells.
  2. Macrophages & dendritic cells engulf pathogens by phagocytosis.
  3. Antigen presentation - these cells then use fragments of the pathogens & express them on their cell membrane.
30
Q

What other way does body detect pathogens?

A

Compliment system

31
Q

Stages of complement system

A

Assists adaptive immune system- destroy extracellular pathogens

Opsonization
- foreign pathogens are marked for phagocytosis
- identifies circulating pathogens expressing same antigens
- dilating of arterioles

Chemotaxis :
- mediated by cytokines
- attraction & movement of macrophages to chemical signal

Cell lysis:
- break down the membrane of pathogen- weakens their ability to proliferate & reduce spread
-phagocytosis

Agglutination:
- uses antibodies to cluster & bind pathogens together
- allows immune cells to attack & weaken infection

32
Q

Which cells produce compliment protein? How do they become activtaed ?

A

Liver cells & macrophages

Over 30 compliment proteins
- circulate in inactive form- so don’t attack body
- activate when pathogen present
- Activated by interacting w/ one another - cascade of activation

33
Q

3 main complement pathways?

A
  1. Lectin pathway – activated by microbial sugars.
  2. Classical pathway – activated by antibodies.
  3. Alternative pathway – activated when some other complement proteins are activated

All 3 pathways work in activating compliment protein C3
- C3 splits into C3a & C3b
- C3a= causes inflammation
- C3b= causes opsonisation & lysis

34
Q

Describe the Classical pathway.

A

Activated when antibodies bind to antigens of pathogen

Compliment proteins- C1q, C1r, C1s- bind to the antibodies

Forms a complimentary complex called C3 Convertase (C4b2a)
- also an enzyme

35
Q

Describe the Lectin pathway

A

Activated by proteins binding to carbohydrates on the pathogen

Forms C3 Convertase (C4b2a)

36
Q

What is the function of C3 convertase?

A

To activate C3 protein

Splits C3 protein into:
- C3a & C3b

37
Q

Describe the alternative pathway.

A

Activated when classical & lecture pathway form C3 Convertase (C4b2a)

C3b binds to surface of pathogen

Forms another type of C3 convertase- different to C4b2a formed by other 2 pathways
- called C3bBb (c3 convertase)

38
Q

What is the role of C3a?

A

Enhances inflammation by stimulating mast cells to secrete histamine

Histamine:
- increases inflammation
- Increases vascular permeability- allows leukocytes to pass more easily
- attracts leukocytes

39
Q

What is the role of C3b?

A

2 roles

1st role- initiate opsonisation
- bind to pathogen surface by forming thioester bond
- so whole pathogen is coated in C3b= opsonisation
- so macrophages can engulfs pathogen easily

However, macrophages can’t engulf pathogen that easily- need help from protein called C5a
- macrophages have 2 receptors- CR1& C5a
- C5a protein binds to C5a receptor
- complex helps macrophage bind to C3b protein through CR1 receptors
- thus allows for phagocytosis

2nd role- formation of membrane attack complex (MAC)
- C3b binds to C3 convertase (C4b2a)
- forms C3/C5 complex
-Complex can either split & activate C3 to form C3a & C3b
- Or cleave & activate C5 to C5a & C5b- this imitates terminal stage- formation of MAC
- MAC being present on pathogen causes it to die via lysis

40
Q

What are interleukins? What are the types?

A

Released bye macrophages & neutrophils

IL1- fever, lethargy, anorexia
IL2 & 12- activate cytotoxic t cells
IL6- lead to release of opsonins from liver
IL 8- activate neutrophils
TNF alpha- activates all of above

PBL Week 3 (10 decks)

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