Flashcards in L22: IgE & Allergy Deck (22):
Type 1 hypersensitivity reaction
another term for allergic response
This portion of the reaction is completely dependent on previous exposure and sensitization
Immediate reaction of Type 1 hypersensitivity
Denotes the ability to transfer reactivity to allergens by means of serum (transfer agent is IgE)
A disease following a response by the immune system to an otherwise innocuous antigen.
Examples of allergic reactions
Mast cells and basophils constitutively express
high affinity IgE Fc receptors
2 major subtypes of mast cells
MCT (tryptase) - found in mucosa
MCTC (tryptase and chymase) - connective tissue
Mast cells contain large amounts of
Inflammatory cytokines (litany)
Name some allergen types
Drugs (eg. antibiotics)
How does the APC (a DC) preferentially activate IgE production programs?
Immunodominant peptides in allergens are preferentially selected by MHC II class D loci, which act IN CONCERT with other non-MHC genes to influence the type of TLR activated, T-helper cell, and cytokine milieu!
Talk to me about the unique context for INITIATING an allergic reaction
Genetic predisposition for atopy. Multiplicity of genes act in concert to produce allergic reaction (bottom line). There's a direct relationship between serum IgE, allergic reaction, and atopic state!
Why does timing of exposure matter?
An unusually high level of exposure
very early in life coupled with a relative LACK of exposure to infectious disease antigens that incite vigorous Th1 and Th2 responses will manifest by IgE production and allergy to some, but not all antigens, in lieu of an expected Th1 or IgG response.
Upon uptake of allergen, DC's secrete what cytokine?
allergic responses are dependent on what Th reaction?
The accelerated production of Th-2 cytokines, especially ____ and _____ dominate the cytokine profile.
IL4 and IL13
What promotes IgE class switching?
Promotion of IgE class switching occurs by up regulation of CD-23 (FcεRII
receptor) on mast cells and basophils that increase their production of IL-4
and IL-13. This is strongly influenced by gene influenced polymorphisms.
What activates activate ε germ-line transcription in B-cells and results in IgE synthesis?
IL4 from Th2, Basophils, and mast cells
What is so special about the FcεR on basophils and mast cells? Hint: think "arming" the FcεR...
The FcεR is the ONLY FcR that can be occupied by antibody not previously complexed with antigen.
What causes cross linking of FcεR on armed basophils or mast cells?
Subsequent exposure to the same allergen then cross-links the IgE previously bound to FcεR receptors.
What triggers degranulation of basophils and mast cells?
Signal transduction activates calcium influx into armed mast cells and basophils which then degranulate, releasing potent vasoactive, inflammatory and