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Allergy

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Information about Allergy
Health & Medicine

Published on November 22, 2008

Author: mohammad.abdul

Source: slideshare.net

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Principles of Immunology Hypersensitivity and Allergy 4/11/06 ”Education is a progressive discovery of our own ignorance”. Will Durant

”Education is a progressive discovery of our own ignorance”.



Will Durant

Word/Terms List Allergens Atopy Erythroblastosis fetalis Reagin Rhogam Serum sickness Tuberculin skin test

Allergens

Atopy

Erythroblastosis fetalis

Reagin

Rhogam

Serum sickness

Tuberculin skin test

Hypersensitivity and Allergy Hypersensitivity -An exaggerated immune response that may cause damage to the host. The trigger is often an innocuous antigen Allergy- A hypersensitive response to an environmental antigen. Often presents as “hay fever”, asthma, dermatitis or anaphylaxis.

Hypersensitivity -An exaggerated immune response that may cause damage to the host. The trigger is often an innocuous antigen

Allergy- A hypersensitive response to an environmental antigen. Often presents as “hay fever”, asthma, dermatitis or anaphylaxis.

Four types of Hypersensitivity Type I IgE-mediated e.g.most common allergies Type II IgG-mediated e.g.ABO transfusion reaction

Type I

IgE-mediated

e.g.most common allergies

Type II

IgG-mediated

e.g.ABO transfusion reaction

Four types of Hypersensitivity Type III Immune-complex mediated e.g.serum sickness Type IV T cell-mediated; delayed type e.g.tuberculin reaction

Type III

Immune-complex mediated

e.g.serum sickness

Type IV

T cell-mediated; delayed type

e.g.tuberculin reaction

 

Type I Hypersensitivity Allergens Proteins Low molecular weight, soluble Atopy -Predisposition to type I hypersensitivity Higher levels of circulating IgE Greater numbers of eosinophils

Allergens

Proteins

Low molecular weight, soluble

Atopy -Predisposition to type I hypersensitivity

Higher levels of circulating IgE

Greater numbers of eosinophils

Type I Hypersensitivity Mechanism Allergen is recognized by naïve B cell B cell stimulated by T helper cell through IL4 IgE specific for allergen is recognized by mast cell Cross linkage of IgE on mast cells Mast cell degranulates

Mechanism

Allergen is recognized by naïve B cell

B cell stimulated by T helper cell through IL4

IgE specific for allergen is recognized by mast cell

Cross linkage of IgE on mast cells

Mast cell degranulates

 

Mast Cell Degranulation Leukotrienes Smooth muscle contraction; vascular permeability Platelet activating factor Activates platelets Histamine Vascular permeability; smooth muscle contraction Cytokines IL4- Stimulates T helper response IL3- Activates eosinophils TNF- Promotes inflammation Chemokines MIP- Attracts macrophages

Leukotrienes

Smooth muscle contraction; vascular permeability

Platelet activating factor

Activates platelets

Histamine

Vascular permeability; smooth muscle contraction

Cytokines

IL4- Stimulates T helper response

IL3- Activates eosinophils

TNF- Promotes inflammation

Chemokines

MIP- Attracts macrophages

 

Mast Cell Receptors Fc epsilon RI Ig superfamily Alpha, beta and gamma chains Alpha chain Two Ig like domains; extracellular Gamma chain Homodimer; two intracytoplasmic tails ITAMs Cross linkages activates PTKs Cell signaling leads to degranulation

Fc epsilon RI

Ig superfamily

Alpha, beta and gamma chains

Alpha chain

Two Ig like domains; extracellular

Gamma chain

Homodimer; two intracytoplasmic tails

ITAMs

Cross linkages activates PTKs

Cell signaling leads to degranulation

 

Type I Hypersensitivity Clinical manifestations Allergic rhinitis Asthma Food allergies Systemic anaphylaxis

Clinical manifestations

Allergic rhinitis

Asthma

Food allergies

Systemic anaphylaxis

 

Prausnitz-Kustner Reaction Described in 1921 Injected allergen caused specific local reaction (Wheal and flare) Called reagins Later identified in 1960’s to be new class of antibody Rabbit Ab against serum from ragweed sensitive individuals could neutralize allergic reaction

Described in 1921

Injected allergen caused specific local reaction (Wheal and flare)

Called reagins

Later identified in 1960’s to be new class of antibody

Rabbit Ab against serum from ragweed sensitive individuals could neutralize allergic reaction

Type II Hypersensitivity Cell associated antigens Transfusion reactions Hemagglutinins Complement mediated Clinical symptoms include fever, chills, nausea

Cell associated antigens

Transfusion reactions

Hemagglutinins

Complement mediated

Clinical symptoms include fever, chills, nausea

 

 

Type II Hypersensitivity Erythroblastosis fetalis Rh+ fetus born to Rh- mother First pregnancy sensitizes Subsequent pregnancies result in anti Rh Ab Mild to severe anemia in fetus Rhogam

Erythroblastosis fetalis

Rh+ fetus born to Rh- mother

First pregnancy sensitizes

Subsequent pregnancies result in anti Rh Ab

Mild to severe anemia in fetus

Rhogam

 

Type II Hypersensitivity Drug induced hemolytic anemia Some antibiotics can be antigenic Bind nonspecifically to RBC surface proteins Ab fixes C and lyses RBCs

Drug induced hemolytic anemia

Some antibiotics can be antigenic

Bind nonspecifically to RBC surface proteins

Ab fixes C and lyses RBCs

Type III Hypersensitivity Soluble antigens complexed with Ab Deposit in tissue or on walls of blood vessels C activation Mast cell binds Fc; degranulates Fc gamma RIII receptors Neutrophils drawn to area; release of lytic enzymes cause type III reaction

Soluble antigens complexed with Ab

Deposit in tissue or on walls of blood vessels

C activation

Mast cell binds Fc; degranulates

Fc gamma RIII receptors

Neutrophils drawn to area; release of lytic enzymes cause type III reaction

Type III Hypersensitivity Serum Sickness Response to foreign protein in serum,e.g horse serum (tetanus antitoxin) Deposition of immune complexes systemically Systemic reactions Fever, vasculitis, arthritis, nephritis

Serum Sickness

Response to foreign protein in serum,e.g horse serum (tetanus antitoxin)

Deposition of immune complexes systemically

Systemic reactions

Fever, vasculitis, arthritis, nephritis

Type III Hypersensitivity Arthus reaction Individual is sensitized to antigen Challenge is administered locally Reaction occurs locally Mast cell mediated

Arthus reaction

Individual is sensitized to antigen

Challenge is administered locally

Reaction occurs locally

Mast cell mediated

 

Type IV Hypersensitivity T cell mediated T helper 1 cells Effector response is through macrophages not T cytotoxic cells Cytokine mediated IL3 Hematopoiesis Interferon, TNF, IL 1 Extravasation MCAF Attracts macrophages MIF Retains macrophages

T cell mediated

T helper 1 cells

Effector response is through macrophages not T cytotoxic cells

Cytokine mediated

IL3 Hematopoiesis

Interferon, TNF, IL 1 Extravasation

MCAF Attracts macrophages

MIF Retains macrophages

 

 

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