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Z MD1 Respiratory block > Immunopathology > Flashcards

Immunopathology Flashcards

1
Q

when are eosinophils involved in allergic responses

A

late

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1
Q

phases of hypersensitivity reactions

A

sensitisation phase effector phase immediate phase late phase: late effector phase

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2
Q

allergic response in airways leads to

A

decreased bronchial diameter and increased mucus –> nasal blockage, coughing, phlegm, asthma

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3
Q

what characterised an atopic patient?

A
  • high levels of IgE - large numbers of eosinophils both in circulation and in tissues - large numbers of IL-4 secreting Th2 cells
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3
Q

very simply, the late effector phase of type 1 immediate hypersensitivity involves

A

eosinophilic activation and recruitment –> mediatorys –> epithelial cell activation, inflammatory cell recruitment and activation

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4
Q

how are allergens usually introduced to a patient

A

via a mucosal route

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5
Q

allergic response in skin leads to

A

increased fluid secretion and vasodilation –> swelling, itching and urticaria

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5
Q

very simply, the effector phase of type 1 immediate hypersensitivity involves

A

IgE binding to mast cells via FcR –> mast cell activation

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6
Q

what causes celiac disease

A

usually HLA DQ2 MHC molecule tTG2 in intestinal lamina propria normally deamidates gliadin peptides to change their glutamine side chain (positive) into glutamate (negative). This negative charge binds effectively to DQ2 on APC –> MALT –> Th1 activation –> cytokines - activate macrophages - damage to the villi

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7
Q

what is an allergy

A

an immune-mediated inflammatory response to common environmental antigens that are otherwise harmless

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7
Q

what molecules are in mast cell granules

A

histamine, heparin, tryptase +/- chymase, TNF-alpha

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7
Q

very simply, the sensitisation phase of type 1 immediate hypersensitivity involves

A

low dose allergen binds APC and basophils to activate Th2 and then initiate IgE

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8
Q

how do granulomas form in type 4 delayed hypersensitivity responses

A

macrophage activation by IFN-gamma results in the production of IL-8, IL-1 and TNF-alpha –> endothelial activation and phagocyte and lymphocyte migration –> TNF-alpha induce weight loss, granuloma formation and death of some infected macrophages

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9
Q

what is the allergen involved in celiac disease

A

gliadin component of gluten

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10
Q

timing of mast cell activation events

A

secretion of preformed mediators - 30-45 seconds synthesis and secretion of lipid mediators - 10-30 minutes synthesis and secretion of cytokines (slow)

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11
Q

what does the persistence of the antigen in the tissue result in

A

the accumulation of T cells and macrophages (via IFN-gamma) in the tissue releasing a lot of cytokines and ROS and RNS

12
Q

what do eosinophils do in the allergic response

A

they produce: - toxic granule-derived basic proteins and free radicals –> tissue damage/remodelling. - chemical mediators –> epithelial activation, inflammatory cell recruitment and activation

12
Q

what does celiac disease cause

A

damage to the vili of the small intestine

13
Q

what is type 4 delayed hypersensitivity responses elicited by

A

a persistent antigenic stimulation (can be infectious agent or chemical agent)

14
Q

what causes attraction and infiltration of eosinophils in allergic responses

A

chemokines by epithelial cells at inflammatory sites

16
Q

where are mast cells located

A

mucosal and epithelial tissues, and near blood vessels

17
Q

what is type 4 delayed hypersensitivity responses characterized by

A

cell mediated, heavy involvement of Th1 cells and macrophages, persistence of the antigen

19
Q

allergic response in GI tract leads to

A

increased fluid secretion and peristalsis –> diarrhea and vomiting

21
Q

what occurs in type 1 immediate hypersensitivity

A

an inflammatory response to allergens mediated by IgE

22
Q

what causes eosinophil activation in allergic responses

A

IL-5 produced by Th2 and mast cells

23
Q

what is the mechanism for type1 hypersensitivity

A

low dose allergen –> introduced via mucosal route –> DCs and basophils promote Th2 helper T cell activation via IL-4 –> TH2 cells produce IL-4, 5 and 13 –> promotes IgE secretion by B cells

25
Q

how do dendritic cells and basophils activate Th2 cells in the sensitisation phase of type 1 hypersensitivity

A

DC binding to T cells produces IL-33 - which activate basophils –> produce IL-4 –> Th2 basophils can also be directly activated by allergen and binds T cells and produce IL-4 –> Th2

26
Q

when mast cells are exposed to IgE initiated by the same allergen, what happens

A

IgE-FcR cross linking –> granule exocytosis (immediate effects) and synthesis of inflammatory lipid mediators (immediate effect, but slower than granules) and cytokines and chemokines (slower effect)

27
Q

what are the 6 main contributors to Type 1 hypersensitivity

A

allergens Th2 cells IgE high affinity FcR Mast cells eosinophils

28
Q

where are eosinophils normally located

A

in mucosal linings in very low numbers

29
Q

allergic response in blood vessel leads to

A

increased blood flow and permeability of the blood vessels in the whole body –> increased tissue fluid and cell infiltrate –> anaphylatic shock

31
Q

4 types of hypersensitivity

A

type 1 - immediate hypersensitivity type 2 - antibody mediated type 3 - immune complex type 4 - delayed type hypersensitivity

32
Q

what are the phases of hypersensitivity

A

sensitization (very rapid) response (has immediate and late phases)

33
Q

allergy treatment options

A
  • adrenaline - anaphylaxis - inhaled beta-adrenergic receptor agonists - asthma - antihistamines (hives, allergic rhinitis) - corticosteroids
34
Q

very simply, the late phase of type 1 immediate hypersensitivity involves

A

induced mediators causing cell infiltration and sustained oedema and/or SM contraction

35
Q

how are mast cells sensitized

A

bind IgE (not bound to allergen) using high affinity FcR (very stable binding - can last for months/years)

36
Q

what do the immediate phase and late phase of mast cell activation lead to

A

immediate - wheal and flare (localized swelling around site of challenge and BV dilation and engorgement) late - cell infiltration and sustained oedema and/or SM contraction

38
Q

what does desensitization/immunotherapy involve

A

administration of increasing doses of allergen to achieve T cell tolerance -> switch to Th1 response

39
Q

very simply, the immediate phase of type 1 immediate hypersensitivity involves

A

wheal and flare due to preformed mediators released by mast cells

Z MD1 Respiratory block (11 decks)

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