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last ever exam > Hypersensitivity > Flashcards

Hypersensitivity Flashcards

1
Q

Type I

A

allergic reaction that occurs minutes to hours after contact with allergen.

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2
Q

what is type I mediated by, which are produced in repsonse to allergen

A

IgE

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3
Q

What do IgE bind to on surface of mast cells and basophils

A

FceRI (high affinity receptors)

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4
Q

5 effector mechanisms underlying type I

A
  1. histamine release
  2. leukotriene release
  3. cytokine release (IL-4/5/13) - recruit th2 cells which make more cytokines and promote more IgE production
  4. eosinophil activation - recruited by IL-5. secrete toxic granules
  5. mucus production
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5
Q

3 type I symptoms

A

sneezing
itching
hives
anaphylaxis

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6
Q

Type II

A

immune-mediated reaction (antibody-dependent cytotoxicity) - kills cells and damages tissues

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7
Q

2 effector mechanisms underlying type II

A
  1. complement activation - forms membrane attack complex to lyse the target cell
  2. ADCC - abs recruit nk cells and macrophages to kill target cell
  3. opsonisation and phagocytosis - antibody-coated target cell recognised and engulfed by phagocytic cells (macrophages and neutrophils)
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8
Q

2 diseases caused by type II

A

HDN
Haemolytic anaemia

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9
Q

2 treatments for type II

A

blood transfusions
immunosuppressive therapy

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10
Q

type III

A

immune-mediated reaction - excess immune complexes in circulation

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11
Q

what do immune complexes activate in type iii, leading to tissue damage and inflammation

A

complement system

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12
Q

3 effector mechanisms underlying type III

A
  1. complement activation - activated by ICs, forms membrane attack complex
  2. neutrophil activation - release enzymes and ROS - damages tissues
  3. platelet activation and aggregation - damages tissues
  4. inflammatory cytokine release (IL1 and TNFa) - tissue damage and inflammation
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13
Q

2 type iii diseases

A

systemic lupus
rheumatoid arthiritis

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14
Q

what is type 4 hypersensitivity known as

A

delayed-type hypersensitivity

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15
Q

when does type 4 occur

A

When there’s a cell-mediated immune response against a foreign antigen + tissue damage

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16
Q

3 effector mechanisms underlying type 4

A
  1. T cell activation - proliferation and differentiation into cytotoxic T cells and t helper cells
  2. Cytotoxic T cell-mediated destruction - destroy cells that display foreign antigen = tissue damage
  3. t helper cell-mediated inflammation - t helper cells secrete cytokines (ifn-g, il-17) - activate macrophages and promote inflammation
  4. macrophage activation - activated by cytokines from T cells. Phagocytosis of foreign antigens and produce cytokines and ROS
17
Q

some mechanisms both th2 immune responses and allergy share

A
  1. IgE production - th2 cells stimulate b cells
  2. eosinophils recruitment - cytokines produced by th2 cells recruit (il5)
  3. mucus production - th2 cells produce il13 - stimulates mucous production
  4. mast cell activation - activated by il4 produced by th2 cells. mast cells degranulate and release inflammatory mediators.
  5. basophils and dendritic cells recruitment - il-9 and il-3 produced by th2
18
Q

what do IgE bind to on surface of mast cells and basophils, leading to their activation and degranulation and cytokines release

A

FceRI receptors

19
Q

how do mast cells play important role in IS

A

releasing histamine and cytokines - recruit other immune cells and clear pathogens

Produce growth factors and cytokines for tissue repair

20
Q

what do eosinophils release once activated

A

release cytotoxic granules, cytokines and chemokine

21
Q

what are main steps in IgE-mediated allergic responses

A
  1. sensitisation - allergen exposure and produce IgE specific to the antigen
  2. re-exposure - allergen binds to IgE on mast cells and basophils upon re-exposure
  3. cross-linking - allergen binds to IgE and IgE receptors cross-link and activates cells
  4. degranulation - granules released by mast cells and eosinophils - allergic reaction symptoms
  5. late phase response - several hours after allergen exposure - recruitment of other immune cells which release cytokines and chemokines that can cause tissue damage
22
Q

what is the main trigger of IgE-mediated allergic responses that leads to mast cell activation and degranulation (allergy symptoms)

A

cross-linking of IgE receptors on the surface of mast cells and basophils by allergens

23
Q

what is atopy the genetic predisposition of

A

to develop allergic diseases like hay fever, asthma and eczema (IgE production - trigger histamine release)

24
Q

when does HDN occur

A

when incompatibilty between blood types of a mother and baby . (woman with Rh-neg is carrying baby with Rh-pos)

25
Q

What develop in the mothers bloodstream in HDN which crosses placenta and attacks fetus RBCs

A

Rh antibodies

26
Q

what is intrinsic allergic alveoli’s

A

allergic lung disease due to inhalation of allergens like dust

last ever exam (10 decks)

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