hypersensitivity

Type I of hypersensitivity

Immediate (allergy, atopic or anaphylactic)

Type II of hypersensitivity

Antibody-dependent

Type III of hypersensitivity

Immune complex

Type IV of hypersensitivity

Cell-mediated or delayed

Antibody involved in type I hypersensitivity

IgE-mediated reactions

Type I Reaction effect on skin

Urticaria and eczema

Type I Reaction effect on Eyes

Conjunctivitis

Type I Reaction effect on Nasopharynx

Rhinorrhea, rhinitis

Type I Reaction effect on Bronchopulmonary tissue

Asthma

Type I Reaction effect on Gastrointestinal tract

Gastroenteritis

How much time does type I reaction takes

@5-30 minutes from the time of exposure to the antigen

Primary cellular component in type I hypersensitivity

Mast cell or basophils

How the type I hypersensitivity reaction is amplified or modified

By platelets neutrophils and eosinophils

What does a biopsy of type I reaction demonstrate

Mainly mast cells and eosinophils

When is the allergic reaction activated

Re-exposure whether by ingestion, inhalation, injection, or direct contact.

Type I reaction is produced by the immediate release of

Histamine, tryptase, arachidonate and derivatives by basophils and mast cells which cause immediate reaction (seconds to minutes)

Type I reaction in terms of location

Local or systemic

Anaphylactic shock leads to

Death

Treatment of type I hypersensitivity

Epinephrine

Antihistamines

Corticosteroids

Type II hypersensitivity is also known as

Cytotoxic

Types of antigen in type II hypersensitivity

Normally endogenous (intrinsic) , annd exogenous(extrinsic like infection with a pathogen) chemicals (haptens) can attach to cell membrane .

Antibodies that bind to antigen in type II hypersensitivity

IgG, IgM

what does happen after the antibodies bind to the antigens?

Form complexes that activate the classical pathway of compliment to eliminate cells presenting foreign antigen.

Then mediators of acute inflammation are generated at the site and membrane attack complexes MAC cause cell lysis, and death.

Mechanisms of antibody mediated type II hypersensitivity

1. Compliment mediated reactions

2. Antibody dependent cell mediated, cytotoxicity

3. Anti antibody mediated cellular dysfunction

What happens in type II hypersensitivity?

the antibodies produced by the immune response, bind to antigens on the patient’s own cell surface

Examples of type II hypersensitivity,

Autoimmune haemolytic anaemia

Hashimoto thyroiditis

Hemolytic disease of newborn

Type III hypersensitivity is known as

Immune complex disease

when does type III hypersensitivity occur?

When immune complex Ag-Ab is not removed from circulation

Immune complex formation may occur as a result of

Autoimmune diseases (rheumatoid arthritis)

Persistence infection (hepatitis virus)

Repeated inhalation of antigenic materials

What are the antibodies involved in type III hypersensitivity?

Aggregations of antigens and IgG and IgM antibodies form in the blood and deposits in various tissue, typically skin, kidney and joints.

What does type III hypersensitivity trigger?

an immune response, according to the classical pathway of compliment activation

The target antigens involved in type II and type III are often

self antigens

Examples of type III hyper sensitivity

Immune complex glomerulonephritis

Rheumatoid arthritis

Systemic lupus erthematosus

Type IV hypersensitivity

Known as cell mediated or delayed type (because it takes two to three days to develop)

Type IV hypersensitivity is mediated by

T cell dependent effector mechanisms involving CD4, TH1, CD8 cytotoxic T cells

What is the classical example of type IV hypersensitivity

Tyberculin (mantoux) reaction.

It peaks 48 hours after injection of antigen.

The lesion is characterized by induration and erythema.

Clinical examples of type IV hypersensitivity

Contact dermatitis like poison ivy rash

Temporal arteritis

Symptoms of leprosy

Symptoms of tuberculosis

Transplant rejection

Examples of disease for a type IV hypersensitivity

Tuberculosis

Leprosy

Blastomycosis

Histoplasmosis

Toxoplasmosis

Leishmaniasis

Granulomas due to infections and foreign antigens

Treatment of type IV hypersensitivity

Corticosteroids and other immunosuppressive agents

Serum IgE antibodies

Determination of it is an essential component for differential diagnosis and for identifying the causative allergens for proper medical treatment

ImmunoCAP (ELISA)

Measurement of igE in human serum

Considered to be the gold standard for the analysis of allergen specific IgE