Allergy L14 Flashcards Preview

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Flashcards in Allergy L14 Deck (22):
1

Define hypersensitivity.

“Excessive immune response that leads to damage”

“Over-reaction of the immune system to harmless agent”

2

What is hypersensitivity in response to? (4)

Response to pathogen

Response to environmental agents

Response to toxin/pharmacological agent

Response to food

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Hypersensitivity Types

Type I  - ____1____

Type II  - ____2____ mediated

Type III - ____3____ complex mediated

Type IV - ____4____ mediated - “delayed type”

1. Immediate

2. Antibody

3. Immune

4. Cell

6

Type 1- immediate hypersensitivity

  • Immediate – occurs within 2 – ___1___ minutes
  • Mediated through ___2___ bound to FcεR1 on:
    • mast cells, basophils, (eosinophils)
    • cells not restricted to a single antigen specificity
    • IgE - FcεR1 binding very high affinity
  • Local inflammation – atopy (allergy)
  • Systemic - ___3___

1. 30

2. IgE

3. Anaphylaxis

7

The reason people collapse during allergic reactions is the increased ____1____ permeability that causes fluid from the blood to leak into the tissues. This leads to less ____2____ in the blood and therefore less gets to the brain  --> collapse (like fainting).

1. Vascular

2. Oxygen

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9

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Early Phase

  • wheal and flare
  • smooth muscle contraction
  • increased vascular permeability
  • mucus secretion

Late Phase

  • post exposure production of inflammatory mediators
  • influx of eosinophils
  • recruit Th2 T-cells
  • Produce IL4 - stimulates B cells to produce more IgE which leads to – chronic/persistent type I response

10

A reason why Type 1 often leads to Type 2 is the increased vascular permeability caused by Type 1 allows the movement of many ________ cells to enter the affected tissues. This congregating of ________ cells can lead to Type 2 and more.

Immune

11

  1. IgE is secreted by ___1___-cells.
  2. IgE binds to basophils, readying them for the binding of ___2___.
  3. ___1___-cells are CD40 positive cells (have CD40 proteins on their surface).
  4. Basophils have CD40 ligands on their surface.
  5. When activated by a cross-linking antigen basophils CD40L binds a ___1___-cell CD40 causing the stimulation of IgE production.
  6. The more IgE production, the more readying of basophils, the more ___1___-cell stimulation and so the more IgE = ___3___ feedback loop.

1. B

2. Antigens

3. Positive

12

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Diagnosis & Treatment: type 1 hypersensitivity

Diagnosis

  • challenge with antigen - “skin prick test”
  • lab test for IgE

Treatment

  • avoidance – desert vacations and sea cruises
  • anti-histamines (hives/bee stings)
  • beta adrenergic agonists (asthma -salbutamol)
  • topical corticosteroids
  • carry epinephrine (adrenaline) syringe - anaphylaxis

Desensitisation (can induce anaphylaxis)

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Type II  - antibody mediated hypersensitivity

  • Occurs in 5 – 6 hours
  • Consequent upon action of IgG & IgM (cytotoxic)
  • Autoimmune disease - Graves’ disease (α-TSHR)
  • Hyper-acute allograft rejection (α-donor HLA)
  • Haemolytic anaemias:
    • haemolytic disease of new-born (α-Rh+)
    • incompatible blood transfusion (ABO)
    • autoimmune haemolytic anaemias
    • response to penicillin

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Type III – (immune complex mediated)

  • Occurs within 2 – 8 hours
  • Soluble protein plus high affinity IgG
    • Pathogen - chronic viral infection (HCV)
    • Environmental/therapeutic agent - penicillin
    • Subcutaneous inoculum - Arthus reaction
    • Auto-antigen – DNA - SLE
  • Localised (Farmer’s Lung) – inhaled Ag - IgG  not E
  • Systemic (serum sickness, HCV, SLE) – lots of Ag

15

Features of type III hypersensitivity

  • Caused by ____1____ complexes – deposited in blood vessels – fix complement and interact with FCR
  • Complement activation:
    • ___2___ activates mast cells - degranulate - urticaria
    • ___3___ recruits inflammatory cells – neutrophils
  • Induration - swelling and hardening of tissue
  • Platelet accumulation – clots – burst vessels - erythema

1. Immune

2. C3a

3. C5a

16

Type IV - cell mediated - hypersensitivity

  • 24-72h after exposure - “delayed type” or “contact”
  • Mediated by T cells - predominantly ____1____ cells
  • Orchestrated by ____2____
  • Examples:
    • Response to M. tuberculosis (tuberculin test)
    • Response to T. radicans (poison ivy/ poison oak)
    • Autoimmunity (later)
    • Transplant rejection (later)

1. Th1

2. Cytokines

17

Why is hypersensitivity often deemed chronic if the reaction is short term?

You will likely have to deal with the allergy for your entire life.

18

Define anaphylaxis.

A rapidly progressing, life-threatening allergic reaction.

19

List the compounds released by basophil degranulation. (4)

  • Histamine (early)
  • Leukotrienes (late)
    • Smooth muscle contraction
    • Increased vascular permeability
  • Cytokines
    • TNF (increased WBC in tissues)
    • IL4 (Th2  T-cells),
    • IL5 (eosinophils)
  • Arachadonic acid
    • Vascular permeability
    • Anaphylactic shock
    • Increased mucus - rhinorhea

20

What are the effects of leukotrienes in hypersensitivity? (2)

  • Smooth muscle contraction
  • Increased vascular permeability

21

What are the effects of arachadonic acid in hypersensitivity? (3)

  • Vascular permeability
  • Anaphylactic shock
  • Increased mucus - rhinorhea

22

What is rhinorrhoea?

What is it commonly known as?

A condition where the nasal cavity is filled with a significant amount of mucus fluid. Occurs relatively frequently.

Commonly known as a runny nose.