Type 1 hypersensitivity Flashcards
Type 1 hypersensitivity
Immediate hypersensitivity anaphylaxis
Type 1 pathologic immune mechanism
IgE antibody
Type 1 mechanism of tissue injury
Mast cell degeneration
Sequence of events in a type 1 hypersensitivity
- exposure to allergen 2. Th 2 activation and ig £ production 3. Ig£ binds to mast cell Fc receptors 4. 2nd exposure 5. Allergen binds to mast cell associated IgE 6. Signal transduction 7. Mediator release 8 end organ effects of mediator
Fc€RI
Binding of IgE to high affinity FCE receptors on mast cells
Enhances half life
Stimulates eosinophil growth and differentiation
GM-CSF, IL-3, and IL-5
Leukocyte chemotaxis
IL-8
Mild local run
“Wheal and flare”, nasal congestion, pruritis, rhinitis, conjunctivitis, asthma
Mild systemic
Generalized pruritis, urticaria, angiodema, vomiting, diarrhea
Severe anaphylaxis
Laryngeal edema, hypotension, schlock, bronchospasm, cardiac arrhythmia, arrest and death
Causes of death from allergic reactions
Asphyxiation from laryngeal edema, suffocation from bronchiolar constriction, or loss of adequate blood pressure from edema
Hyposensitization mechanisms
- Blocking antibodies, 2. Spe civic suppressor T cells, 3. Th2 to Th1 switch
IgE production
Th2 dependent.
IL-4 release from Th2 cells
Activation of IgE producing B cells
Mast cells
Reside in tissue, mononuclear, heavily granulated
Basophils
Circulating version of mast cells, poly nuclear, granulated
Pre-formed mediators
Immediate release and effect
Histamine, serotonin, ECF-A, Heparin
Histamine
Pre-formed mediator; causes smooth muscle contraction or relaxation, increase vascular permeability, pruritis, and increased exocrine secretions
Newly synthesized mediator
Delayed response
Arachidonic acid, leukotrienes B, C, and D, prostaglandins and thromboxanes, il-4, gm-csf, il-3, il-5, il-8
Antihistamines
Compete with histamine for histamine receptor sites
Cromolyn sodium
Stabilizes mast cell membranes -preventing degranulation
Corticosteroids
Prevent the arachidonic acid pathways
Epinephrine
Reverse effects of histamine on smooth muscle constriction and relaxation in vasculature
Omalizumab
Humanized anti-lgE antibody - inhibits the binding of IgE to FCERI on surface mast cells
Singular
Lenkotriene receptor antagonist
Desensitization versus immunotherapy
desensitization= triggering sublethal release to increase dosage without harm
Immunotherapy = introducing the immune system to the allergen over a long period of time
