HYPERSENSITIVITY AND EVALUATION

METHODS

APARNA.SM.PHARMACYG.PULLA REDDY COLLEGE OF PHARMACY

2

HYPERSENSITIVITY Hypersensitivity reaction resulting from

specific interactions between antigens (allergens) and either antibodies or sensitized lymphocytes.

Hypersensitivity reaction resulting from specific interactions between antigens (allergens) and either antibodies or sensitized lymphocytes

Diffuse urticaria Anaphylactic response to bee sting

TYPE –IMast cell degranulation mediated by antigen cross-linking of IgE bound to IgE Fc receptors (FcRI).

Mediators released during activation of mast cells.

MECHANISM IN TYPE-I

(A)Electron micrograph of normal mast cell illustrating large monocyte-like nucleus and electron-dense granules.

(B) (B) Mast cell that has been triggered and is beginning to release contents of granules, as seen by their decrease in opacity and formation of vacuoles connecting with exterior.

ELECTRON MICROSCOPIC VIEW

Clinical Examples

Hay fever and Asthma----To pollen, house dust, pets etc.

Urticaria(Hives)---Drugs,food. Reddening and itching of skin.

Systemic anaphylaxis---Inj. of Penicillin,Insect bites.

Type II IgE-mediated

THREE TYPES OF MECHANISMS IN TYPE- II HYP

Drug-Induced Reactions:Adherence to Blood

Components

complementcomplement

blood cell adsorbed drug blood cell adsorbed drug or antigen drug metaboliteor antigen drug metabolite

antibody to drugantibody to drug

lysis

DISEASES OF TYPE-II

Autoimmune hemolytic anemia Thrombocytopenia Erythroblastosis fetalis Goodpasture's syndrome

Hemolytic Disease of the New Born

RhD-ve mother

RhD +ve fetus

Anti-RhD Abs

RhD +ve fetus

‘A’ blood group mother

‘B’ blood group fetus

Anti-B Abs

If mother and fetus have different blood groups, hemolytic disease does not occur.

Prophylaxis (RhoGAM)

RhD-ve mother

RhD +ve fetus

Anti-RhD Abs

RhD +ve fetusMid-term injection of RhoGAM and a second injection within a few days of delivery

Immune Complex Mediated Hypersensitivity-III

Type III hypersensitivity mechanism

Type III hypersensitivity mechanism

Examples of Type-III

Serum sickness Arthus reaction Systemic lupus erythematosus (SLE) Glomerulonephrites

Serum sickness

Systemic lupus erythematosus

DELAYED TYPE -IV

TYPE IV OR DTH– REACTION TO POISON IVY

Examples of Type IV

Contact dermatitis Tuberculin skin test Chronic transplant rejection Multiple sclerosis

Contact Dermatitis

ECZEMA

ALLERGIC SKIN REACTIONS

Leprosy

Hyporesponse

Normal response

Hyper response

Fluid filled blebs with bacteria

small skin lesion

Severetissue damage

Type V Hypersensitivity / Auto immune

This is an additional type that is sometimes used as a distinction from Type 2

Instead of binding to cell surface components, the

antibodies recognize and bind to the cell surface receptors , which either prevents the intended ligand binding with the receptor or mimics the effects of the ligand, thus impairing cell signaling

Examples of Type V Grave's disease Myasthenia Gravis Hashimoto's thyroiditis Systemic lupus erythematosus

OECD TEST GUIDE LINESOECD TEST GUIDE LINES

EVALUATION OF HYP :QUALITATIVE

LYMPH NODE:QUANTITATIVE ASSAY

* The basic principle is to induce proliferation of lymphocytes in the lymph nodes draining the site of test substance application.

* This proliferation is proportional to the dose and to the potency of the applied allergen and provides a simple means of obtaining a quantitative measurement of sensitization.

* Proliferation is measured by comparing the mean proliferation in

each test group to the vehicle treated control (VC) group.

* The ratio of the mean proliferation in each treated group to that in the VC group, termed the SI, is determined, and should be ≥1.8.

* The methods described here are based on the use of measuring ATP content by bioluminescence to indicate an increased number of proliferating cells in the draining auricular lymph nodes

* The bioluminescent method utilises the luciferase enzyme to catalyse the formation of light from ATP and luciferin according to the following reaction:

ATP+LUCIFERIN+OXYGEN luciferase

OXYLUCIFERIN+AMP+Ppi+CO2+LIGHT

* The emitted light intensity is linearly related to the ATP concentration and is measured using a luminometer* The luciferin-luciferase assay is a sensitive method for ATP quantitation used in a wide variety of applications.

IN-VITRO SCREENING METHODS

REFERENCES Willey drug safety evaluation (2002)by shayne c.Gad OECD (2010), Skin Sensitization: Local Lymph Node Assay,

Test Guideline No. 429, Guidelines for the Testing of Chemicals, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]

http://iccvam.niehs.nih.gov/docs/immunotox_docs/llna/llnarep.pdf]

OECD (1992), Skin Sensitisation, Test Guideline No. 406, Guidelines for Testing of Chemicals, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]

OECD (2002), Acute Dermal Irritation/Corrosion, Test Guideline No. 404, Guidelines for Testing of Chemicals, OECD, Paris. Available at: [http://www.oecd.org/env/testguidelines]