IgE Immunology Flashcards
Allergic reactions are Type __ hypersensitivity reactions
Type 1
The ability to transfer reactivity to allergens by means of serum
Atopy
IgE has binding sites for these high affinity receptors
Fc epsilon
Number of Fc regions on the Fc for binding
2 (CH4 and CH3)
Basophils are circulating ________
Leukocytes
Major subtypes of mast cells
MC(T) cells (tryptase)
MC(TC) cells (tryptase and mast cell-specific chymase)
Location of MC(T) cells
Mucosa of respiratory and GI tracts. Increase with inflammation
Location of MC(TC) cells
Connective tissue (dermis, submucosa of GI tract, heart, conjunctivae, and perivascular tissues)
Common component of many of the environmental antigens
They contain chitin-polysaccharide (not found in mammals)
Immunodominant peptides are presented in which loci
Class II D MHC loci by dendritic cells, in concert with non-MHC genes
Genetic dictation of response of child with 2 atopic parents
50%
Likelihood of child with no atopic parents becoming atopic
15%
Sites of tight control of IgE serum levels
MHC linked genes, maternal genes on chromosome 11, and others
3 keys to developing an allergy
1) Exposure (high level of exposure early in life, combined with relative lack of exposure to disease antigens that elicit Th1 and Th2 responses)
2) Route (delivery to mucosal surfaces)
3) Genetic predisposition
Cytokines that are produced in allergic reaction
IL-4, instead of IL-12. DC cells uptake allergen via “allergic” TLR
Cytokine profile of allergic reaction
IL-4, IL-13
IL-4 is the critical signal from the Th-2 cell to an allergen specific B-cell
These can produce IL-4, which then activate epsilon germ-line transcription in B-cells, resulting in IgE synthesis
Mast cells, basophils, and Th2
Promotion of IgE class switching via up-regulation of this
CD23, aka Fc epsilon RII receptor
Arming vs. activation of Fc epsilon receptors cells
Arming: binding to high affinity IgE Fc receptors
Activating: cross-linking the IgE previously bound to Fc epsilon R receptors by subsequent receptors.
Signal transduction activates these subsequent steps
Ca2+ influx into armed mast cells/basophils
Degranulation of potent vasoactive, inflammatory, and fibrogenic mediators
High affinity IgE Fc receptor
FcεRI
Low affinity IgE Fc receptor
FcεRII
This IgE Fc receptor controls B cell growth and differentiation
FcεRII
This IgE Fc receptor plays a critical role in promoting degranulation and phagocytosis
FcεRI
Immediate allergic reaction
Release of prostaglandin and leukotrienes
Direct complement activation by tryptase cleavage
Late phase is completely dependent upon ____________
T-cell activation
Cytokines IL3, 4, 5, 13, TNF-alpha, CM-CSF, and IL-10
Characteristic of late allergic reaction
Eosinophils, neutrophils, additional mast cells, basophils, and lymphocytes
Role of IL-5 in late allergic reaction
IL-5 stimulates release of eosinophils from bone marrow, and augments effects of eotaxin
Increases Fc epsilon R display
Unique inflammatory enhancers produced by eosinophils
Major basic protein (also called PRG2), leukotrienes, and cationic proteins
Skin lesions that occur when IgE armed mast cells are activated in the skin
Urticaria, aka hives
Allergin binding to cells in nasal submucosa, inciting chronic allergic inflammatory reaction driven by continuous aeorallergen exposure
Allergic rhinitis
IgE armed cells recruited to submucosal sites of pulmonary bronchi
Acute and chronic bronchial asthma
The MOST important factor in arriving at the correct diagnosis in cases concerning allergy
Careful clinical history
NOT the most important factor in arriving at the correct diagnosis in cases concerning allergy
Blood/skin tests
RAST
Blood test with solid-phase allergen and radio-labeled anti-IgE
These types of exposures to allergen dominate
Mucosal
ONLY FcR THAT CAN BE OCCUPIED BY ANTIBODY WITHOUT ANTIGEN
Fc epsilon receptor
Important type of immunotherapy
SLIT (sublingual immunotherapy) or SCIT (subcutaneous immunotherapy)
Difference between angioedema and urticaria
Angioedema is lesion below the skin
