Hypersensitivities - Ray Flashcards
Type I hypersensitivities are mediated by___.
IgE
Type II hypersensitivities are mediated by ___.
IgG + CTLs
Type III hypersensitivities are mediated by ___.
Immune complex (complement)
Type IV hypersensitivities are mediated by ___.
Macrophages Th1/Th17 cells
First allergen exposure is referred to as ___.
Sensitization
Allergy vs. atopy
Allergy refers broadly to any exaggerated immune response to an Ag regardless of the mechanism. Atopy refers to IgE-mediated allergies and all type I hypersensitivities are atopic.
Common assays to detect IgE allergens
Skin Prick Test (SPT) or RadioAllergoSorbant Test (RAST) / ImmunoCap
Type I hypersensitivity Reaction
- Isotype switching of B-cells induced by IL-4 secretion by Tfh cell.
- B-cell differentiates into plasma/memory B-cell and secretes IgE.
- IgE binds to Fc receptors on Mast cells.
- Ag binding to bound IgE causes crosslinking and degranulation.
What induces class-switching of antibodies?
IL-4 and AID (activation induced cytidine deaminase).
Where are mast cells found?
Tissues, not blood.
Types of mast cells
Mucosal and connective tissue
Downstream signaling of mast cell activation
- Granule exocytosis
- Secretion of lipid mediators
- Secretion of cytokines
Recruitment of Th2 cells occurs when in an allergic rxn?
Late phase
The presence of allergens in the bloodstream results in
systemic anaphylaxis
Treatments for allergies
- Avoidance
- Desensitization
- Blocking effector pathways
- Supportive measure (treatment of symptoms).
