Download Hypersensitivity type I

Types of hypersensitivity
diseases
 The type of immune response and
immunologic mechanisms that causes
tissue injury
 The nature and location of the antigen
that is the target of this response.
Types of hypersensitivity
diseases
 Immediate H.S (Type I) caused by IgE
 Type II H.S caused by antibodies other than
IgE can cause tissue injury and interfering with
normal cellular functions.
 Type III H.S caused by deposition of circulating
Immune complexes in tissues
 Type IV or Delayed type hypersensitivity
caused by T cells and Macrophages
Disease caused by
Immune responses
*Activation of Th2 cells and production of
IgE
*Allergen
Activation of Th2
B
cell activation
IgE
binding of IgE
to Fc receptor reexposure to Allergen
release of mediators
pathologic
reactions
General features (1)
‫‪Immediate‬‬
‫‪hypersensitivity‬‬
‫‪ ‬با ورود آلرژن ‪ ،‬سلولهای ‪B‬‬
‫آن راشناسایی وپس از فعال‬
‫شدن ‪ ،‬آنتی بادی ‪ IgE‬ترشح‬
‫میکنند ‪.‬‬
General features(2)
 There is a strong genetic predisposition for the
development of immediate hypersensitivity
*high level of IgE synthesis often run in families
• Class –II MHC alleles
• One locus for atopy is on chromosome 5,near
the site of gene cluster encoding the IL-3,IL-4,
• IL-5,IL-9,IL-13 and IL-4R
‫‪General features‬‬
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‫افراد آتوپیك یا آلرژیك در مقابل عوامل آنتي ژنیك شایع‬
‫محیطي ‪،‬پروتئین هاي موجود در گرده گیاهان)‪(pollen‬‬
‫‪ ،‬مواد غذایي ‪ ،‬فضوالت حیواني‪ ،‬سم حشرات یا برخي‬
‫داروها از طریق ‪ Th2‬پاسخ میدهند‬
‫آلرژنها پروتئینهاي ریز مولكول با حاللیت باال‬
‫ایمني ذاتي را فعال نمي كنند‬
‫فراواني در محیط وبرخورد مكرر‬
‫گلیكوزیالسیون باال‬
َAllergens
 Type I is dependent on the activation of Th2
cells
 The clinical and pathologic manifestations of
Type I:increased vascular
permeability,vasodilation,smooth muscle
contraction,local inflammation
Mast cell activation
‫‪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,proteoglyca
ns(heparin and chondroitin sulfate)
 Synthesis and secretion of lipid
mediators(prostaglandines ,Leukotrienes)
 Synthesis and secretion of cytokines(IL3,4,5,6,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
features
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Hay fever(allergic rhinitis)
Increased peristalsis
Bronchial asthma
Anaphylaxis
Wheal and Flare reaction
Skin test(PK test)
Therapy
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Inhibiting mast cell degranulation
Antagonizing the effects of mediators
Reducing inflammation
Desensitization
Anti IgE as a therapy
 Severe allergic reactions during
anesthesia are fortunately rare, occurring
only once in every 5,000 to 25,000
anesthetics. Unfortunately, these
reactions can sometimes be fatal, with a
3.4% mortality
 Anaphylaxis during general (asleep)
anesthesia presents in a similar way but there
are three unique features:
 First, the patient who is asleep cannot tell us
about light-headedness or breathlessness
 Second, during a typical general anesthetic,
many drugs are given, and it is hardly ever
clear which of these drugs have caused the
reaction
 Third, during anesthesia there are many other
potential causes for the blood pressure to be
 Treatment may include insertion of a breathing
tube, administration of intravenous fluids, and a
variety of drugs, the most important of which is
epinephrine (adrenaline). Early and appropriate
treatment is almost always successful.
 drugs are not the only cause of allergic
reactions, and a recently recognized cause of
anaphylaxis is allergy to natural rubber (or
`latex`). Reactions to latex are a special
problem during anesthesia as surgical gloves
are usually made of this material.
Food Allergy
Introduction to food allergies
 When people have an unpleasant reaction to something they ate,
they often think that they have an allergy to the food. Actually,
however, only about 10-15% of adults and children have clinically
proven true allergic reactions to food.
 This difference between the prevalence of clinically proven food
allergy and the public's perception of the problem is due primarily
to misinterpreting food intolerance or other adverse reactions to
food as food allergy
 A true food allergy is an abnormal response to food that is
triggered by a specific reaction in the immune system and
expressed by certain, often characteristic, symptoms.
 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
 Food allergy
 food poisoning
 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, particularly tuna and mackerel.
 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
 monosodium glutamate (MSG)
 and sulfites.
The allergens in food
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Resist the heat of cooking
The acid in the stomach
The intestinal digestive enzymes.
The allergens survive to cross the
gastrointestinal lining
 enter the bloodstream,
What are the most common
food allergies?
 In adults, the most common foods that
cause allergic reactions are shellfish,
such as shrimp, crayfish, lobster, and crab;
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.
What is cross-reactivity?
 Cross-reactivity is the occurrence of
allergic reactions to foods that are
chemically or otherwise related to foods
known to cause allergy in an individual.
What are the symptoms and
signs of food allergy?
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All of the symptoms of food allergy occur within a few minutes to an hour
of eating.
A food allergy can initially be experienced as an itching in the mouth and
difficulty swallowing and breathing.
Then, during digestion of the food in the stomach and intestines,
symptoms such as nausea, vomiting, diarrhea, and abdominal pain can
start.
Incidentally, the gastrointestinal symptoms of food allergy are those that
are most often confused with the symptoms of different types of food
intolerance.
the allergens are absorbed and enter the bloodstream. When they reach
the skin, allergens can induce hives or eczema, and when they reach the
airways, they can cause asthma.
As the allergens travel through the blood vessels, they can cause
lightheadedness, weakness, and anaphylaxis, which is a sudden drop in
blood pressure.
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What was the timing of the reaction? Did the reaction come on quickly, usually within an hour
after eating the food?
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Was treatment for allergy successful? For example, if hives stem from a food allergy,
antihistamines should relieve them.
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Is the reaction always associated with a certain food?
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Did anyone else get sick? For example, if the person has eaten fish contaminated with histamine,
everyone who ate the fish should be sick. In an allergic reaction, however, only the person allergic
to the fish becomes ill.
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How much did the patient eat before experiencing a reaction? The severity of the patient's
reaction can sometimes relate to the amount of the suspect food eaten.
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How was the food prepared? Some people will have a violent allergic reaction only to raw or
undercooked fish. A thorough cooking of the fish destroys those allergens in the fish to which they
react, so that they then can eat it with no allergic reaction.
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Were other foods eaten at the same time as the food that caused the allergic reaction? Fatty foods
can delay digestion and thus delay the onset of the allergic reaction.
 Cromolyn sodium
 Theophyllin blocks phosphodiesterase
 epinephrin
How is food allergy
diagnosed?
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History
Elimination diet
Skin tests
Blood tests
Food challenge
 scratch test
to test a number of potential allergens at one time
Inexpensive
less sensitive
The size of the hive may correlate with the intensity of the
allergic reaction.
In the event of a severe reaction, the allergist will administer a
rescue medication such as epinephrine or an antihistamine
necessary to remove the patient from an anthihistamine
medication regimen
 RAST test or radioallergosorbent
 expensive
 considered as accurate as food challenges
 they are considered a very safe way to test for food
allergies
 less sensitive than skin prick tests
 a positive RAST test will be often be confirmed
with a food challenge
 RIST(radiolabeled Immunosorbent test)
 The suspected allergen is bound to an insoluble material and the patient's
serum is added. If the serum contains antibodies to the allergen, those
antibodies will bind to the allergen. Radiolabeled anti-human IgE
antibody is added where it binds to those IgE antibodies already bound to
the insoluble material. The unbound anti-human IgE antibodies are
washed away. The amount of radioactivity is proportional to the serum
IgE for the allergen.
 RAST are often used to test for allergies when:
• a physician advises against the discontinuation of medications that can
interfere with test results or cause medical complications;
• a patient suffers from severe skin conditions such as widespread
eczema or psoriasis; or
• a patient has such a high sensitivity level to suspected allergens that any
administration of those allergens might result in potentially serious side
effects.