Mod12: Anaphylactic vs Anaphylactoid Reactions - Clinically Important Mediators Flashcards
Anaphylactic vs Anaphylactoid Reactions
List clinically Important Mediators of Anaphylactic vs Anaphylactoid Reactions
Histamine
Arachidonic Acid Metabolites
Tryptase
IgE antibodies
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Which receptors do Histamine affect?
H1 & H2 receptors
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Stimulation of which Histamine receptors will cause:
Release of Nitric oxide causing vasodilation
Increased capillary permeability
Airway constriction
Smooth muscle contraction
H1
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
True or False: stimulation of H1 receptors causes vascular smooth muscle contraction
False
Stimulation of H1 receptors does Not cause vascular smooth muscle contraction
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Stimulation of which Histamine receptors will cause:
Vasodilation, Cardiac stimulation (tachycardia), and Gastric acid secretion?
H2
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
True or False: stimulation of both H1 and H2 receptors causes vasodilation
True
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
What is the main physiologic source of Histamine?
Mast Cells
Histamine is also produced by Basophils

Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Where in the body are Mast cells abundant?
Airways
Skin
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
What’s the function of mast cells?
Make & release many mediators
(e.g., Histamine)
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
What cause mast cells to release mediators?
Triggered by antigens, drugs
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Which specific mechanism causes mast cells to release Histamine
Mast cells are anchored into the tissue (airway, skin, intestin). Mast cells will have IgE antibodies on their surface. Antigens will attach to the mast cell. This will trigger the mast cell to release histamine
Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
What percentage of circulating granulocytes are Basophils?
0.5 - 1%

Mediators of Anaphylactic vs Anaphylactoid Reactions - Histamine
Similar to mast cells, what do basophils have on their surface that will detect antigen (triggers) floating in the circulation and lead to Histamine release?
IgE
Mediators of Anaphylactic vs Anaphylactoid Rx - Arachidonic Acid Metabolites
Which two Arachidonic Acid Metabolites are associated with allergic reactions
Leukotrienes & Prostaglandins
(Breakdown products of arachidonic acid)
Mediators Anaphylactic vs Anaphylactoid Rx - Arachidonic Acid Metabolites
Which arachidonic acid metabolites mediate allergic reactions characterized by:
- Bronchoconstriction - More intense than histamine*
- Increased capillary permeability*
- Vasodilation*
- Coronary vasoconstriction*
- Myocardial depression*
Leukotrienes
Mediators of Anaphylactic vs Anaphylactoid Reactions
Which arachidonic acid metabolites mediate allergic reactions that result in more intense bronchoconstriction?
A. Histamine
B. Leukotrienes
A. Histamine
B. Leukotrienes
Mediators Anaphylactic vs Anaphylactoid Rx - Arachidonic Acid Metabolites
Which arachidonic acid metabolites mediate allergic reactions characterized by:
Vasodilation, Bronchospasm**, Pulm HTN, Increased capillary permeability
Prostaglandins
Mediators Anaphylactic vs Anaphylactoid Rx - Arachidonic Acid Metabolites
Which arachidonic acid metabolites mediate allergic reactions that may result in bronchospam?
A. Leukotrienes
B. Prostaglandins
A. Leukotrienes
B. Prostaglandins
Mediators Anaphylactic vs Anaphylactoid Rx - Tryptase
What’s a benefit of Tryptase?
Serves as an excellent marker of histamine release
Mediators Anaphylactic vs Anaphylactoid Rx - Tryptase
Normally what are blood levels Tryptase?
Undetectable
Mediators Anaphylactic vs Anaphylactoid Rx - Tryptase
What do elevated serum levels of Tryptase indicate?
That mast cell activation with mediator release has occurred
Mediators Anaphylactic vs Anaphylactoid Rx - Tryptase
What trigger elevation of serum levels of Tryptase?
Anaphylactic or anaphylactoid reactions
Mediators Anaphylactic vs Anaphylactoid Rx - Tryptase
What’s the plasma half-life of Tryptase?
2 hour
Mediators Anaphylactic vs Anaphylactoid Rx
Which antibodies, present on mast cells and basophils surface cause mediator to be released?
Immunoglobulin E (IgE)
Mediators of Anaphylactic vs Anaphylactoid Rx - IgE
Do Anti IgE antibodies exist?
Yes
Anti IgE antibodies were first introduced in 2002
Mediators of Anaphylactic vs Anaphylactoid Rx - IgE
Why are Anti IgE antibodies not used more commonly?
Very expensive!!!
Mediators of Anaphylactic vs Anaphylactoid Rx - IgE
Anti IgE antibodies are only approved for use in which medical condition?
Allergic asthma
Mediators of Anaphylactic vs Anaphylactoid Rx - IgE
How are Anti IgE antibodies admnistered?
Parenterally
Anaphylactic vs Anaphylactoid Reactions - Apex Review
In which type of hypersensitivity allergic reaction do we note:
- Antigen antibody interaction in a patient who has been previously sensitized to the antigen.*
- IgE mediated reaction.*
- Examples: anaphylaxis, extrinsic asthma*
Type I: Immediate Hypersensitivity
Anaphylactic vs Anaphylactoid Reactions - Apex Review
What’s the best lab test to determine if an allergic response has occurred?
Tryptase
It is released from mast cells during an allergic reaction
Anaphylactic vs Anaphylactoid Reactions - Apex Review
In which type of hypersensitivity allergic reaction do we note:
- IgG and IgM antibodies bind to cell surfaces or extracellular regions.*
- The reaction activates the complement cascade.*
- Examples: ABO-incompatibility, heparin-induced thrombocytopenia*
Type ll: Antibody-Mediated
Anaphylactic vs Anaphylactoid Reactions - Apex Review
In which type of hypersensitivity allergic reaction do we note:
- An immune complex is formed and deposited into the patient’s tissue (normally these complexes are cleared from the body).*
- The reaction activates the complement cascade.*
- Examples: snake venom reaction, protamine induced vasoconstriction*
Type III: Immune Complex Mediated
Anaphylactic vs Anaphylactoid Reactions - Apex Review
In which type hypersensitivity allergic reaction do we note:
- Allergic reaction is delayed at least 12 hours following exposure.*
- Examples: contact dermatitis, graft-vs-host reaction, tissue rejection*
Type IV: Delayed
Anaphylactic vs Anaphylactoid Reactions - Apex Review
Type IV: Delayed hypersensitivity allergic reactions are delayed for at least how long after exposure?
12 hours
Anaphylactic vs Anaphylactoid Reactions
Visual representation of mediators, effects and presentations
(see picture!!!)
Note mediators, effects and presentations
