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Atopy and Allergic diseases. Prof. Mohamed Osman Gad El Rab. College of Medicine & KKUH. Terminology التعريف :. Human disease caused by immune responses to environmental antigens that lead to : immediate reactions in the target tissues - PowerPoint PPT Presentation
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Terminology التعريف :
Human disease caused by immune responses to
environmental antigens that lead to :
immediate reactions in the target tissues & rapid onset of symptoms
are called :
allergic diseases .
With reference to Coombs & Gell classification of hypersensitivity these are :
Immediate ( type I )hypersensitivity reactions .
In clinical practice these reactions are commonly called :
allergy or atopy .
atopy : is derived from a Greek term (atopos ) which mean : out of place .
The term refer to :
a strong genetic predisposition - استعدادfor development of immediate hypersensitivity اهبه
reactions in certain individuals.
The genetics of allergy are complex , involving interactions between several genes .
studies of atopic families have identified regions
on chromosomes 11q and 5q هذهالحساسيه لفرط المسببه .الكروموسومات
فرط بتكوين وعالقته كروموسوم كل وظيفه:الحساسيه
chromosome 11q : encodes the b subunit of
the high affinity IgE receptor.
chromosome 5q : contain many cytokine genes that
increase susceptibility حساسيه .
The high- affinity IgE receptor encoded by chromosome 11q .الجاذبيه ) ) عالي ليس ولكنه اي جي اي يوجد الحساسين غير االشخاص في
الحساسين االشخاص مثل العدد وكثير
مسبب الحساسيه
2يرتبطب اي) ) جي اي
The 5q locus موقع contain genes for : - IL-3 ,4, 5 , 9 & 13 .
-These cytokines : - promote تعزز TH2 سيلز هلبر responses by تي
enhancing تنميه : * IgE isotype switching in B cells. * eosinophils survival . * mast cell proliferation .
- variation in the IL-4 gene has been associated with high levels of IgE in atopic individuals.
عده ) ) – \ على وتؤثر البيضاء الخاليا من تنتج كميائيه ماده هو االنترلوكين االول البلوك من تذكيراو لالنقسام بنتشيطها اما عليها وتؤثر المناعي بالجهاز عالقه لها خاليا هي االهداف هذه اهداف
وهي اخر لشكل تحويلها او النشط للشكل للتحول جسم- تنشيطها على خاص بريسيبتور ترتبطكثرت . اذا المناعي الجهاز باثاره عالقه لها يكون وبذلك الهدف الخليه
Allergy is a systemic disorderالعرض شغل
NosePharynx
Stomach
EsophagusLungs
SkinFood allergyFood allergy
Allergic rhinitisAllergic rhinitisAsthmaAsthma
EczemaEczemaUrticariaUrticariaAllergic dermatitisAllergic dermatitis
skin
Respiratory system
GIT
Clinical presentation االعراض:
atopic individuals may present with one or more of the following conditions :
- allergic rhinitis.
- allergic conjunctivitis وهو العين التهابمناعي بسبب . دائما
- allergic asthma.
- atopic dermatitis ( eczema (.
A newborn approximate risk of developing symptoms according to family history of allergic disease :
1. no family member allergic 5-15 %.
2. one sibling allergic 25-35 %.
3. one parent allergic 20-40 %.
4. both parents allergic 40-60 %.
5. both parents allergic ,
( same symptom ( 50- 70 %.
Epidemiology الوبائيات :
The prevalence االنتشار of allergic disease worldwide ranges
from 30% to 40%.
There is substantial قطعي evidence برهان that the incidence حدوث of allergy is steadily ببانتظام increasing all over the world .
A study in U.K. between 2001-2005 showed that the
incidence of patients with at least one allergic disease
increased from 18.9% to 24.2 %.
J R Soc Med. 2008, 101(11(:558-563.
A study in Saudi Arabia documented a significant increase in incidence :
Allergic asthma:
From 8% (in 1986 ( to 23% (in 1995(. ( p <.0001 (.
Allergic rhinitis: From 20% (in 1986 ) to 25% ( in 1995). (p < .003).
A.R.Al-Frayh,Z.S hakoor,M.O.GadElRab.Annal of Allergy, Asthma &Immunology, 2001,86:292-296.
* Allergic disease is the 5 th leading chronic disease
among all ages .
* And the 3rd chronic disease among children under
18 years old ; up to one child in three is affected .
* Trend انه الى يشير indicate that by 2015 half of الميلall Europeans
may be suffering from an allergy ( مسوي مساكييينمنها ) . طالع
Antigens that elicit تثير allergic reactions are called allergens
because they have the following features :
1. low molecular weight.
2. glycosylation القاموس the formation of : منlinkages with glycosyl groups.
3. high solubility in body fluids .
4. proteins, in nature ,or chemicals bound
to proteins , and some have enzyme
activity .
House dust mite &Cockroach صرصور insects :
Common indoor allergens that may cause allergy symptoms All through the year . ( perennial ( .
Honey-bee black( fire ( ant . Common causes of anaphylaxis وفوري شديد ظهورالحقا ) ) تفصل .. للحساسيه
Manifestations ظهور of allergic disease require two steps .
1. sensitization phase : االولى االصابه first exposure to allergen.
2. challenge phase : الالحقه االصابه re-exposure to allergen .
Sequence of events in immediate H/S reactions.
First exposure to allergen.
Activation of TH2 cells & stimulation of IgE class switching in B –cells .
Binding of IgE to FcR1 on mast cells.
sensitization .
Sequence of events in immediate H/S reactions.
Repeated exposure to allergen
Activation of mast cells : release of mediators .
challenge .
Allergic reactions can be divided into immediate and
late- phase responses .
- the immediate response start within seconds
and is due to preformed mediators.
- the late reaction ,which takes up to 8-12 hours to
develop , is due to induced synthesis and release
of mediators & cytokines .
The immediate response :
due to preformed &rapidly synthesized Mediators .
start within seconds.
The late-phase response :
due to synthesis of new mediators (PG,(LT.,( chemokines& cytokines, withInflux تدفقof eosinophils and T-cells .
takes 8-12 hours to develop.
clinical presentations :
- allergic rhinitis .
- allergic asthma .
- skin allergy .
- food allergy .
- systemic anaphylaxis .
Allergic rhinitis :
inhaled allergens activate mucosal mast cells
beneath the nasal epithelium .
mediators released .
diffuse across the mucous membranes of the nasal
passages .
The immediate reaction in allergic rhinitis is characterized by :
1. intense شديده itching & sneezing .
2. local edema (leading to blocked nasal passages(.
3. nasal discharge سيوله ( typically rich in eosinophils (.
4. irritation تهيج of the nose ( as a result of histamine( .
A similar reaction to airborne allergens deposited تدخل in the conjunctiva of the eye can result in :
allergic conjunctivitis.
Allergic asthma :
inhaled allergens activate submucosal mast cells in the lower airways . mediators released within seconds & lead to :
contraction of bronchial smooth muscles. (bronchial constriction – difficulty in breathing (.
increased secretion of mucus .
increased vascular permeability .
influx تدفق of inflammatory cells ( including eosinophils & TH2 cells (.
An important feature of asthma is chronic inflammation of the airways .
This result from the influx of inflammatory cells .
TH2 cells .IL-9 & IL-13 .
eosinophils .Major basic protein
neutrophils .proteolytic E.
Lung epith. Cells .Rantes & eotaxin .
These cell products act on
1. Airway smooth muscle cells .2. Lung fibroblasts . 3. Mucous glands .
and cause :
airway remodeling .
Airway remodeling :
thickening of the airway walls by hyperplasia & hypertrophy of the smooth muscle layer
Goblet cell metaplasia .
Development of fibrosis .
Increased mucus permanent narrowing of the permanent secretion . airways . tissue damage.
Irreversible lung damage .
Hyperreactive airways react to non- specific
factors:
chemical irritants .
smoke & Strong perfumes .
sulphur dioxide & air pollutants.
viral & bacterial respiratory infections .
Skin allergy :
manifest as : - acute urticaria .
- chronic eczema .
* allergens enter the epidermis or dermis by :
1. a stinging insect .
2. direct contact .
3. through the blood ( ingested food or drug (.
local connective tissue mast cells become
activated & release mediators .
* mediators activate local increase in
local nerve endings. vasc. permeability.
- vasodilatation of extravasation of
blood vessels. fluid from blood.
( redness of the skin. ( ( Swelling of the skin.(
this skin lesion is called :
wheal انتفاخ-and flare حمره reaction .
Acute urticaria : كله الجسم حول تنتشر
a disseminated متبعثر form of the wheal-and- flare
reaction .
sometimes appear when ingested allergens
enter the blood stream and reach the skin .
Histamine released by mast cells in the skin
causes :
large , itchy red swellings of the skin.
( urticaria or hives (.
Food allergy :
A significant مهم health problem especially in children .
In USA food allergy cause approximately 30,000
anaphylactic reactions each year , including 200
deaths .
* food allergens resist مقاوم digestive enzymes & therefore reach the mucosal surface of the small intestine as an intact molecule .
Ingested allergens in food cause activation of mucosal
mast cells in the gastrointestinal tract .
mediators released .
transepithelial fluid loss smooth muscle contraction.
diarrhea . vomiting .
Ingested food allergens may enter the bloodstream
and cause systemic reactions .
activation of connective disseminated mast cell
tissue mast cells in the activation .
skin .
urticaria . generalized anaphylaxis.
Systemic anaphylaxis ( anaphylactic shock).
Allergens may be introduced directly into the
bloodstream as a result of :
- penicillin injection ( مهب المحقون الدواءبنسلين ) . شرط
- honey-bee sting .
disseminated منتشر mast cell activation .
شائعه : اسبابلحدوثها
massive mediator release into the blood result in :
wide spread increase airway swelling of the
in vascular permeability . Constriction. larynx
loss of blood pressure . difficulty in suffocation. (hypotension( . Breathing ( difficulty in breathing (.
this condition can be rapidly fatal but can be controlled by العالج * immediate injection of epinephrine ( adrenaline ( .
Diagnosis : التشخيص
1. skin prick test (SPT(.
2. specific IgE measurement .
3. challenge tests.
4. elimination – provocation tests.
( food allergy (.