Download Hypersensitivity type I

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Nutrition wikipedia , lookup

Hunger wikipedia , lookup

Overeaters Anonymous wikipedia , lookup

Hunger in the United States wikipedia , lookup

Food safety wikipedia , lookup

Obesity and the environment wikipedia , lookup

Freeganism wikipedia , lookup

Food studies wikipedia , lookup

Local food wikipedia , lookup

Food politics wikipedia , lookup

Food choice wikipedia , lookup

Food intolerance wikipedia , lookup

Transcript
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫آلرژی چیست؟‬
‫مکانیسم القاء آلرژی چگونه است؟‬
‫آلرژی غذایی چیست؟‬
‫مهمترین آلرژن های غذایی‬
‫ویژگیهای آلرژن های غذایی‬
‫تولرانس نسبت به مواد غذایی تابع چه عواملی است ؟‬
hypersensitivity type I
*Allergen
Activation of Th2
B cell activation
IgE
binding of IgE to Fc receptor
reexposure to Allergen
pathologic reactions
release of mediators
General features
‫‪Immediate hypersensitivity‬‬
‫‪ ‬با ورود آلرژن ‪ ،‬سلولهای ‪B‬‬
‫آن راشناسایی وپس از فعال‬
‫شدن ‪ ،‬آنتی بادی ‪ IgE‬ترشح‬
‫میکنند ‪.‬‬
Mast cell activation
Factors involve in H.S type I
 Allergene
 Th2 cells
 Mast and basophil cells
 FcR-I
 Mediators
 Genetic predisposition
 cytokines
‫‪Eosinophil and Basophil‬‬
‫‪ ‬اين سلولها داراي گيرنده هاي ‪high‬‬
‫‪ affinity‬براي ‪ IgE‬بنام ‪ FCR‬مي‬
‫باشند‬
‫‪ ‬گرانولهايي سيتوپالسمي كه حاوي آنزيم ها‬
‫و ساير مدياتورهاي فارماكولوژيك‬
Mast cell activation
 Rapid release of granule contents (degranulation)such
as Histamine,tryptase, chymase,proteoglycans(heparin )
 Synthesis and secretion of lipid
mediators(prostaglandines ,Leukotrienes)
 Synthesis and secretion of cytokines(IL-3,4,5,6,TNF-)
Mediators actions
 Histamine= bronchoconstrictor,vascular
leak,intestinal hypermotility
 PGD2=vasodilator and bronchoconstrictor ,
neut. Chemotaxis
 LTC4=bronchoconstriction,inflammation
 PAF=bronchoconstriction ,vasodilator,
inflammation
clinical and pathologic
manifestations of Type
 increased vascular permeability
 Vasodilation
 smooth muscle contraction
 local inflammation
Clinical and pathologic features
 Hay fever(allergic rhinitis)
 Increased peristalsis
 Bronchial asthma
 Anaphylaxis
Wheal and Flare reaction
Introduction to food allergies
 Actually, only about 2-10 % of adults and children have
clinically proven true allergic reactions to food.
 food intolerance or other adverse reactions to food
 A true food allergy
 People who have food allergies must identify and
prevent them because, although usually mild and not
severe, these reactions can cause devastating illness
and, in rare instances, can be fatal.
 Food intolerance refers to an adverse physiologic response to a food
and may be due to inherent properties of the food
a)toxic contaminant
b)pharmacologic active component
 or to characteristics of the host
a)metabolic disorders
b)idiosyncratic responses
c)Psychological disorder
**** they may not be reproducible
*** they are often dose dependent.
Food allergy refers to an abnormal immunologic response to a
food that occurs in a susceptible host.
a)These reactions are reproducible each time the food is ingested
b) they are often not dose dependent
 Histamine toxicity: Some natural substances (for





example, histamine) in foods can cause reactions
resembling allergy. Histamine can reach high levels in
cheese, some wines, and certain fish
Food additives: Another type of food intolerance is an
adverse reaction to certain compounds that are added to
food to enhance taste, provide color, or protect against the
growth of microorganisms.
The compounds most frequently tied to adverse reactions
that can be confused with food allergy are :
yellow dye number 5(tartrazine)
monosodium glutamate (MSG)
and sulfites.
What are the most common food
allergies?
 In adults, the most common foods that cause
allergic reactions are shellfish, such as shrimp,
lobster, nuts from trees, such as walnuts; fish; eggs and
peanuts.
 In children, the pattern is somewhat different from
adults, and the most common foods that cause allergic
reactions are eggs, milk, peanuts, and fruits,
particularly tomatoes and strawberries.
Food allergy varieties
 Based on the immunological mechanism involved,
food allergies may be further classified in :
a)IgE-mediated
b) Cell mediated
c) mixed IgE mediated-cell mediated when both IgE
and immune cells are involved in the reaction
 IgE-mediated classic food allergic reactions are
those that are:
 immediate
 reproducible
 and readily diagnosed by detection of food-specific
IgE
Characteristics common to “major” food allergens are that :
 they are water-soluble glycoproteins, are 10 to 70kD in





size
and are relatively stable to heat, acid, and proteases.
Frequent exposure
High glycosylation
In addition, the presence of immunostimulatory factors in
the food may also contribute to such sensitization.
However, the biochemical characteristics of a food
allergen cannot explain alone , as only a minority of
patient exposed to it develop allergy.