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Physiology and anatomy > Immune System > Flashcards

Immune System Flashcards

1
Q

what is the first line of defence?

A

skin, lining of the lungs or gut, urogenital tract

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2
Q

what is the second line of defence?

A

mobilisation of host immune cells

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3
Q

what is the third line of defence?

A

humoral and cell-mediated systems

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4
Q

explain the first line of defence in more detail and explain how physical, chemical, mechanical and commensal mechanisms help to protect against pathogens.

A

physical: generally epithelial membranes, eg the skin- tough barrier for pathogens to penetrate; tight junctions form a seal against the external environment. mucosal membranes are thick and sticky and contain glycoproteins called mucins.
mechanical: flushing effect eg tears and urine, peristalsis and cilia
commensal: compete with pathogens for nutrients and epithelial attachment sites
chemical: pH (acid in stomach and alkali in the gut), fatty acids, bile salt, lysolipid.

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5
Q

briefly summarise the stages of the second line of defence

A
  • inflammation and fever
  • cellular response
  • soluble/chemical mediators
  • complement
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6
Q

explain the vascular response of the ‘inflammation and fever’ stage of the second line of defence

A

1) vascular response
- chemoattraction begins to recruit more effector cells and molecules of the innate response to boost mobilisation from the blood into the tissues
- clotting of small blood vessels further downstream to stop microbes from spreading around the body

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7
Q

explain how the physical response of the ‘inflammation and fever’ stage of the second line of defence helps to fight pathogens

A

runny nose, sweating and vomiting are examples of increased flushing mechanisms and boosts the 1st line of defence

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8
Q

explain how a fever can help to fight pathogens/infections (second line of defence) - inflammation and fever stage

A

pyrogens alter the thermostat setting of the hypothalmus which leads to an increase in body temperature.

this can accelerate the action of host enzymes which lead to speeding up of immune responses, and inhibit microbial growth whose optimum temperature is around 35 degrees celsius.

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9
Q

what type of cells are involved in the cellular response?

A

-macrophages
-monocytes
-neutrophils
-basophils
dendritic cells
-NKs

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10
Q

what is the role of macrophages?

A
  • usually resident in the tissue
  • phagocytes that preferentially recognise prokaryotic cells
  • strong citric burst so very good at breaking down ingested organisms
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11
Q

what is the role of monocytes?

A
  • found in peripheral circulate
  • respond to inflammation
  • differentiate into macrophages in tissue
  • boost macrophage populations
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12
Q

what is the role of neutrophils?

A
  • most common in WBC in circulation and usually the first to respond to inflammation
  • degranulates and releases a lot of lytic enzymes but these often damage the host tissue more than the invading organism
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13
Q

what is the role of basophils?

A
  • different types of granulocytes
  • attack parasitic/multicellular organisms
  • release histamine
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14
Q

what is the role of dendritic cells?

A
  • phagocytose but limited due to restricted recognition and less lytic capacity
  • sample fluid eg looking for antigenic debris
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15
Q

what are the 4 different types of soluble mechanisms involved in the second line of defence?

A

1) bactericidial
- lysozyme, secretory phospholipase A2, defensins, lactoferring

2) opsonisation
- mannose binding lectin, C reactive protein

3) anti-viral
- IFN

4) complement
C3 and C4

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16
Q

What do bactericidal soluble mediators do?

A
  • present in tears, saliva and phagocytes
  • attack peptidoglycan and phospholipids in bacterial cell wall leading to direct lysis
  • defensins are a collection of peptides that can disrupt bacterial cell walls making them leaky and vulnerable
  • lactoferrin cholates iron
17
Q

what does opsonisation achieve?

A
  • mannose binding lectin/c-creative protein acute phase proteins
  • latch onto bacteria so WBCs that lack PRRs can recognise
18
Q

what do antiviral soluble mediators do?

A

IFN reduce resistance in neighbouring cells - upregulate expression of NK receptors to enhance activation of NK cells to target virally infected cells

19
Q

what does complement achieve in the second line of defence?

A

1 - activation of macrophages and inflammation

2 - cytolysis ; target cell death

3 - increased adaptive immunity T and B cell

4 - opsonisation - bacteria and phagocytes

5 - Ab/Ag complex removal

20
Q

how does innate immunity activate the adaptive immune system?

A
  • macrophages have PRRs that recognise PAMPs; instigates phagocytosis
  • phagosome fuse with lysosome to form phagolysosome which breaks the microbe into distinct antigens
  • MHC determines individuals tissue type and presents antigenic material on the surface of the cell (antigen presenter cell)
  • lymph usually only recognise Ag when presented on MHC
  • Helper T cells can then go on to activate more effector lymphocytes such as B cells and cytotoxic T cells
21
Q

what types of T lymphocytes are there and what do they do?

A
  • memory
  • regulatory
  • natural killer cells
  • Th1 helper T cells - activate macrophages
  • Th2 helper T cells - activate B cells
  • Cytotoxic T cells - attack infected host cells
22
Q

give some differences between cell-mediated and humoral response

A

1) Targets
- CM: intracellular antigens
- Hm: Extracellular anitgens inc. toxins

2) Main Cells
- CM: cytotoxic T cells NK cells
- Hm: B cells and plasma cells

3) Activation
- CM: secretion of cytokines
- Hm: secretion of antibodies

4) Effects
- CM: direct cell lysis, enhanced cell resistance
- Hm: normal antibody functions

5) primary vs secondary response
- CM: Memory T cells
- Hm: memory B cells

23
Q

how does the binding of antibodies to antigens inactivate the antigen?

A
  • neutralisation; blocks the vial binding sites, coats bacteria
  • agglutination of microbes
  • precipitation of dissolved anitgens

(these 3 enhance phagocytosis)

-activation of complement system which leads to cell lysis

24
Q

how does the lymphatic system activate an adaptive immune response?

A
  • capillary bed around all organs of the body that provides nutrients etc in the interstitial fluid
  • some of that fluid drains into the lymphatic system to form lymph and is transported to lymph nodes. this allows lymphocytes resident in the lymph nodes to sample the interstitial fluid, looking for antigens
  • if Ags present, that would activate an adaptive immune response
  • if not present, lymph is drained back into the vascular system
25
Q

where does afferent lymph flow from and to?

A

flows from the tissues to the lymph nodes

26
Q

where does the efferent lymph flow from and to?

A

flows from the lymph nodes back to the vascular system, eg draining into the subclavian veins

27
Q

what is haematopoiesis?

A

commitment and differentiation processes that lead to the formation of all blood cells from haematopoietic stem cells

28
Q

what are the 2 mechanisms in which lymph fluid is moved within the lymphatic system?

A

1) rhythmic contraction of smooth muscle that surrounds the large lymph vessels
2) muscular activity around the smaller lymph vessels that squeeze fluid

29
Q

what is immunological redundancy?

A

the fact that if one immunological mechanism fails or is circumvented, another can take its place

30
Q

briefly explain how macrophages distinguish self from non-self in order to preferentially target invading bacteria

A
  • macrophage can distinguish prokaryotic cells from eukaryotic
  • they express PRRs that bind to carbohydrates/sugars typically nor expressed by self-cells known as PAMPs through opsonisation
31
Q

explain the process of leukocyte extravasation that allows neutrophils to leave circulation and enter the tissue

A

-danger signals such as IL-1 establish a chemotactic gradient and induce endothelial cells to express selectins/CAMs;

neutrophils have low affinity receptors to these that bind and break, causing the cell to roll along the vessel wall

PAF activates the integrin on the cell surface that binds to ICAM1 stopping or tethering the cell

endothelial vessels become leaky due to expansion of tight junctions allows the cell to migrate into the tissue in a process known as diapodesis

32
Q

state 3 ways that soluble mediators of the immune response can help combat infection

A
  • direct bactericidial properties
  • damaging or distrupting bacterial cell wall
  • act as opsonins

extras

  • chelating irons
  • ctivating compelent that can lead to direct cell lysis
  • boosting resistance of neighbouring cells to viral infection

Physiology and anatomy (5 decks)

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