Rola Hmede Allergy Flashcards
Define allergy (hyper sensitivity/ sensitivity)
Certain dzs in which immune responses to harmless environmental Ags causes tissue inflammation and organ dysfunction
An allergen is any Ag that causes allergy
T or f
T
Allergen can be only a complete protein Ag
F
It can be a complete protein Ag ( pollen and animal dander)
Or low molecular wt proteins
That can elicit an IgE response
Atopy
Inherited propensity to respond immunologically to such common naturally occurring Allergens with continuous production of IgE Ab
How do the allergen enter the body
Thru
Ingestion
Inhalation
Skin contact
Injection
Based on mechanism and time taken for the reaction we can distinguish 4 types of allergic rxn
T or f
T
Type I Hypersen (immediate and anaphylactic Hypersensitivity )involves IgG and IgM
T or f
F
It involves IgE
Type I hypersen always takes too much time from allergen exposure to symp appearance
F
-The rxn usually takes 15-30mins (secs to minutes after exposure)
-Although sometimes it may have delayed onset (10-12hrs) —> if allergen causes a rxn after it is partially digested
-VERY RARE CASES rxn develop after 24hrs
What are the main cells involved in type I hypersen
Mast cells and basophils, they are mainly seen on a biopsy from rxn site
Where are these cells mostly located
In the :
-skin
-mucosa of resp
-mucosa of GI tract
In these areas the atopic rxn localizes the most
Also when mast cells are stimulated by exercise, emotional stress and chemicals this rxn is called hypersensitivity rxn
F
These rxns are mediated by agents without IgE allergen interaction so they are not hypersensitivity rxns although they produce same symptoms
List the 4 major mediators produced by mast cells that cause the pathophysiology of the immediate and late phases of atopic dz
Histamine
Tryptase
Proteoglycans (heparin, chondroitin sulfate)
Chemotactic factors
The mediators can activate more WBC
T
They have effects on local tissue and organs and activate more WBC defenders
If the release of mediators is sudden and extensive the rxn is sudden and severe
T
What are the clinical effects of histamine
Binds to H1 and H2 and causes:
-prurits
-increased vasopermeabiility and vasodilation (cutaneous vasodilation)
-contraction of smooth muscles in airway and GI tract
-nasal and airway mucus production
-gastric acid secretion
Tryptase is a protease that is produced by the mast cell can it can cleave C3 and C3a
T
Tryptase is only present in mast cell
F
It can be present in other few cells
What is the role of heparin
Imp in storing the preformed protease and play a role in production of alfa tryptase
Chemotactic factors are for both easinophils and neutrophils
T
-Chemotactic factor of anaphylaxis: easinophilic chemotactic factor
-Inflamm factor of anaphylaxis:
Neutrophil chemotaxis
What are common allergens in Hypersen type I
Pollen
Animal dander
Insect bite
Bee sting
Food (nuts and shellfish)
Meds
Plants
1st time of exposure leads to a very severe rxn
F
Mild reaction occurs in 1st time of exposure
Repeated exposure leads to a more serious rxn (for IgE to form and bind the surface of mast and basophil)
One person is sensitized, even a very limited exposure to a very small amount of allergen can trigger a severe rxn
T
Allergic rxns are always very severe
F
Mild or severe
Localized or generalized
What are main symps
Allergic rhinitis
Allergic asthma
Allergic gastroenterophathy
Urticaria
Angioedema
Anaphylaxis
