Hypersensitivity/ Allergy Flashcards
(72 cards)
State of heightened reactivity to antigen
Hypersensitivity
immune responses to innocuous antigens that lead to symptomatic reactions upon re-exposure
hypersensitivity reactions
damage to host tissue caused by hypersensitivity reactions to typically innocuous antigens
hypersensitivity disease
Involves IgE-dependent triggering of mast cells
Immediate Type/ Type I hypersensitivity
Commonly referred to as allergy
Immediate Type/ Type I
Involves IgG antibody that is reactive with cell-surface or matrix antigens
Type II: Altered Self
involves production of antigen:antibody complexes
type III: Immune complex
altered host hypersensitivity
Type II: altered self
immune complex hypersensitivity
type III: Immune complex
T cell mediated hypersensitivity
Type IV: Delayed type
delayed type hypersensitivity
Type IV: Delayed Type
Antigens that elicit a Type I hypersens. response are called
allergens–> slectively stimulate Th2 cells that can drive class switching from IgM to IgE (weakly opsonizing/low dose/extracellular)
Main cell type involved in type I hypersensitivity upon first encounter with the antigen
Th2 CD4+–> b/c it can promote class switiching to IgE which is taken up by the high affinity IgE receptor on mast cells etc…
Type I hypersensntitivity MOA
Antigen selectively stimulates a TH2 response that drives class switiching to IgE specific for the encountered antigen
- ->then mast cells take up the IgE ab’s on their FCgammaR1 (high affinity IgE receptor)–>second exposure to Antigen–> massive degranulation of MAST CELLS
- TH2 driven IgE responses
Common features of most allergens
- Small
- Highly Soluble
- Carried on Dessicated particles (stable)
- diffuse into the mucosa from the particles
High or Low dose exposure for allergens?
Low Dose ( will cause Th0 to become a TH2)
Th2 release which cytokines
3 4 5 10 13 TGF beta
Many common allergens have______
enzymatic activity
IgE is important in the immune response to _____
parasites
(They produce proteases that aid in the parasites own movement through the host’s tissue–>therefore, IgE response to protein allergens is largely physiologic–> but becomes pathologic in response to innoccuous environmental allergens
protein (enzymatic*) allergen +TH0–> TH2–>promotes class switching in Naive B lymphocytes to IgE specific to that protein
know that
One of the pre-requisites for Type I hypersensitivity is that the initial response must be….
IgE response
How does class switiching to IgE occur
TCR of an Effector CD4 TH2 t cell becomes ligated (by specific peptide antigen presented on MHC II molecules) on the B cell (an antigen presenting cell)–> TH2 secretes IL-4, 5, and 13–> mediates class switching to IgE
All the cells hat can INITIATE Type I Hypersensitivity reaction
Mast Cells (primary)
Eosinophils
Basophils
–>all of these have the high affinity IgE FC receptor
Cross-Linking of IgE receptors on a mast cell, basophil and eosinophil leads to what?
degranulation of granules that contain mainly histamine…Leukotriens, Prostaglandins, TNF, Cytokines, PAF and neutral proteases