7/27/2019 Hypersensitivity_(Human Physiology)_Presentation_by Biomedical Association of Students for Excellence(BASE)

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Starting With That Great Name ,

Whose Help We Solicit . . .

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Presented By:

ASAD ALI SIYAL

 Department of Biomedical Engineering ,

 Mehran University of Engineering & Technology (MUET),

 Jamshoro, Sindh, Pakistanengrasadsiyal@yahoo.com

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Presentation Contents:

Hypersensitivity (Introduction)

Types

I (Immediate Hypersensitivity) II (Antibody Mediated Hypersensitivity) 

III (Immune-Complex Mediated Hypersensitivity) IV (Cell-Mediated Hypersensitivity)

Summary

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INTRODUCTION

HYPERSENSITIVITY:

Hypersensitivity refers to excessive, undesirable (damaging, discomfort-producing and sometimes fatal) reactions produced by the normalimmune system. Hypersensitivity reactions require a pre-sensitized(immune) state of the host.

Hypersensitivity reactions can be divided into four types:Type - I

Type - IIType - IIIType - IV

based on the mechanisms involved and time taken for the reaction.

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TYPE – I(Immediate Hypersensitivity) 

- It is also known as immediate or anaphylactic hypersensitivity

- The reaction may involve skin (urticaria and eczema), eyes (conjunctivitis),nasopharynx (rhinorrhea, rhinitis), bronchopulmonary tissues (asthma) and

gastrointestinal tract (gastroenteritis).

- It cause “Immediate Allergic Reactions”, which may lead to anaphylaxis, shock,edema, dyspnea death

1) Allergen exposure2) IMMEDIATE phase: MAST cell DEgranulation, vasodilatation, vascular leakage,

smooth muscle (broncho)-spasm3) LATE phase (hours, days): Eosinophils, PMNs, T-Cells 

Reaction Time: It takes duration of seconds to minutes. 

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TYPE – II(Antibody Mediated Hypersensitivity) 

-It is also known as cytotoxic hypersensitivity and may affect a variety of 

organs and tissues.

- It is primarily mediated by antibodies of the IgM or IgG classes and

complement

- It results when antibodies are directed against antigens on the surface of 

cells or other tissue components.

-These reactive antigens may be Intrinsic antigens or reactive antigen

Effects:

It can have a variety of detrimental effects , including inflammation,

opsonization and phagocytosis

Reaction Time:

It takes duration of minutes to hours. .

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TYPE – III(Immune complex-mediated hypersensitivity)

-It is also known as immune complex hypersensitivity.

•- It is mediated by soluble immune complexes. They are mostly of the

IgG class, although IgM may also be involved.

- Type III hypersensitivity diseases are some of the most common

immune-mediated diseases.

-In these diseases, complexes of antibodies and antigens in circulation

deposit in the vascular walls of blood vessels leading to inflammation.

- The reaction may be the pathogenic mechanism of diseases caused by

many microorganisms.

Reaction Time:

The reaction may take 3 - 10 hours after exposure to the antigen 

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TYPE – IV(Cell-Mediated Hypersensitivity) 

-Type IV hypersensitivity is also known as cell mediated or delayed type

hypersensitivity.

-The classical example of this hypersensitivity is tuberculin (Montoux)

reaction

-It is also involved in the pathogenesis of many autoimmune and infectious

diseases

- It can be classified into three categories depending on the time of onset

and clinical and histological presentation

1. T lymphocytes2. Monocytes

3. Macrophages

Reaction Time:

It takes 48 hours after the injection of antigen  

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SUMMARY

Type - I Acute allergic reaction

Type - II Antibodies directed against cell surfaces

Type - III  Immune complexes

Type -IV  Delayed Hypersensitivity, e.g., Tb skin test

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