Lecture 27: Type I Hypersensitivities Flashcards
hypersensitivity
exaggerated, innapropraiate or prolonged immune response to an antigen (or allergen)
2 phases of hypersensitivity
- sensitization
- effector
clinical manifestations of hypersensitivities plus any tissue damage that may result are due to….
immune response to the allergen
hypersensitivity reactions are recognized based on the _____ of immune response and the _____ of the target antigen
type, location
Type I hypersensitivity is ________ and mediated by _______
immediate, IgE
Type II hypersensitivity is _______ and mediated by_____or_____
cytotoxic, IgG or IgM
What is Atopy
inappropriate hypersecretion of IgE in response to allergens
individuals w/ atopy are atopic
what is the hygiene hypothesis of atopy
preveleance of atopic disorders increses as the environemnt becomes more hygienic (lack of microbial diversity)
In Type I sensitization phase, the initial exposure to allergen elicits a _____response
TH2
B-cell activation results in secretion of ______
IgE
IL____&____, secreted from effector Th2 cells induce class-switching to ______
IL-4 & IL-13, IgE
IgE binds into ______ on the surface of mast cells, causing mast cells to become sensitized
FcεRs
mature mast cells reside in _____ throughout the body
Connective tissue
are there any clinical manifestations during the sensitization phase
no
During the Effector Phase, on ____exposure to the same allergen, the allergen ______ IgE bound FcεRs on mast cells
repeat, crosslinks
Mast cell activation results in…
- Release of granular contents (histamine)
- Synthesis and release of other mediators (Lipid mediators, cytokines)
Granules contain preformed ______ & ________
histamine & proteases
what is the major mediator in granules
histamine
biological effects of histamine occur within ________ and is part of the ______Phase reaction
seconds, early phase reaction
biological effects of histamine include
- vasodilation
- increased vascular permeability
- non-vasculature sm contraction
- increased mucus secretion
Histamine binds to _____receptors
H1
_______block histamine binding to H1 receptors
Antihistamines
Mast cells begin to synthesize _____ and _____ within minutes of stimulation
prostaglandins (PGs) and leukotrienes (LTs)
biological effects are similar to histamine, but much more potent and longer-lasting
corticosteroids inhibit the synthesis of ______and ______
PGs and LTs
prednisone, prednisolone, dexamethasone
NSAIDs block the synthesis of …..
PGs
carprofen, meloxicam, deracoxib
main cytokines synthesized by mast cells
INF and IL-6: inflammation
IL-4 & IL-13: Th2, IgE
IL-5:Eosinophils
several hours after stimulation by allergen
cytokines are responsible for the ____phase reaction
late
cytokines cause inflammatory response by recruiting and activating _______and _______
neutrophils & eosinophils
can cause tissue damage
what are corticosteroids used to prevent
damaging inflammation caused by inflammatory cytokines
acute, hypersensitive allergic reaction to an antigen
Anaphylaxis
reactions manifest differently based on location of the allergen
localized anaphylaxis
local release of mediators
- clinical manifestations depend on site of allergen exposure and location of mast cell activation
Systemic anaphylaxis
systemic release of mediators
- systemic clinical manifestations result from the allergen being in/spread throughout the **bloodstream **
allergic rhinitis and allergic conjunctivitis are a result of activation of mast cells where
upper respiratory tract and eyes
itchy, watery eyes, sneezing, runny nose
treatments for allergic rhinitis and allergic conjunctivitis include..
antihistamines and corticosteroids (also antimicrobials if infection inspected)
allergic asthma is a result of mast cell activation where
lower respiratory tract causing bronchocontriction and increased mucous secretion
coughing, wheezing, open mouth breathing
treatment for allergic asthma includes..
bronchodilators(fast acting)
corticosteroids (prevent late stage response)
Atopic dermatitis and urticaria (Hives) results from mast cell activation where
in the skin
(complications often due to self trauma - hair loss, scaling, hyperpigmentation, secondary infections)
itchy, red, dry, inflammed skin lesions
treatments for atopic dermatitis and urticaria include
- corticosteroids
- antihistamines
- cyclosporine A
- oclacitini
- lokivetmab
Food allergies result from activation of mast cells where…
GI Tract
treat systemic anaphylaxis with ______ first
epinephrine
- vasoconstriction
- relaxes bronchial sm
- increases HR and BP
- inhibits mast cell degranulation
adjunctive txt include: antihistamines, corticosteroids, bronchodilators
Intradermal skin tests observes development of _____and _____
wheal and flare
immunoassays can be performed to measure total_____ or allergen-specific____levels within the serum
IgE, IgE
what is allergen immunotherapy (hyposensitization therapy) and what is the goal
administration of increases doses of allergen
goal is to alter the immune response to the allergen
allergen immunotherapy results in the induction of Treg cells that function to suppress what
- mast cells, basophils, eosinophils
- effector helpter T cells (esp Th2)
- tissue inflammation and mucous production
- inflammatory DCs
Suppressing Th2 cells decreases _____production by B-cells and promotes_______production
IgE, IgG
Type III hypersensativities are ________mediated cytotoxicity
immune mediated
(IgG or IgM)
Type IV hypersensativity is _______type and ______Cell mediated
delayed
T-cell mediated
mast cell activation causes the release of lipid mediators which synthesize ________ & _________
prostaglandins and leukotrienes
