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Allergy - Pathophysiology

Allergy - Pathophysiology: Encyclopedia II - Allergy - Pathophysiology

All hypersensitivities result from an aberration somewhere in the normal immune process. The exact cause of such malfunctions is not always apparent, however, and several arguments from genetic-basis, environmental-basis and intermediate proponents exist with varying validity and acceptance. Allergy - Acute response. The difference between a type I hypersensitivity reaction against an allergen to the normal humoral response against a foreign body is that plasma cells secrete IgE as opposed to either IgM (a ...

Allergy, Allergy - History, Allergy - Signs and symptoms, Allergy - Diagnosis, Allergy - Skin test, Allergy - Problems with skin test, Allergy - Total IgE count, Allergy - Treatment, Allergy - Immunotherapy, Allergy - Chemotherapy, Allergy - Alternative therapies, Allergy - Pathophysiology, Allergy - Acute response, Allergy - Late-phase response, Allergy - Basis of the allergic response, Allergy - Genetic Basis, Allergy - Relationship with parasites, Allergy - Basis of increasing prevalence, Allergy - The hygiene hypothesis, Allergy - Increasing use of chemicals, Allergy - Common allergens

Allergy, Allergy - Acute response, Allergy - Alternative therapies, Allergy - Basis of increasing prevalence, Allergy - Basis of the allergic response, Allergy - Chemotherapy, Allergy - Common allergens, Allergy - Diagnosis, Allergy - Genetic Basis, Allergy - History, Allergy - Immunotherapy, Allergy - Increasing use of chemicals, Allergy - Late-phase response, Allergy - Pathophysiology, Allergy - Problems with skin test, Allergy - Relationship with parasites, Allergy - Signs and symptoms, Allergy - Skin test, Allergy - The hygiene hypothesis, Allergy - Total IgE count, Allergy - Treatment, Atopy, Multiple chemical sensitivity (MCS)., Food allergy, Hypoallergenic, Hay fever, Soy allergy

Allergy: Encyclopedia II - Allergy - Pathophysiology

Allergy - Pathophysiology

Allergy - Acute response

The difference between a type I hypersensitivity reaction against an allergen to the normal humoral response against a foreign body is that plasma cells secrete IgE as opposed to either IgM (against novel antigens) or IgG (against immunized antigens). IgE binds to Fc receptors on the surface of mast cells and basophils, both involved in the acute inflammatory response.

When IgE is first secreted it binds to the Fc receptors on a mast cell or basophil, and such a IgE-coated cell is said to be sensitized to the allergen in question. A later exposure by the same allergen causes reactivation of these IgE, which then signal for the degranulation of the sensitized mast cell or basophil. These granules release histamine and other inflammatory chemical mediators (cytokines, interleukins, leukotrienes, and prostaglandins) into the surrounding tissue causing several systemic effects, such as vasodilation, mucous secretion, nerve stimulation and smooth muscle contraction. This results in the previously described symptoms of rhinorrhea, itchiness, dyspnea, and anaphylaxis. Depending on the individual, allergen, and mode of introduction, the symptoms can be system-wide (calliscal anaphylaxis), or localised to particular body systems (for example, asthma to the respiratory system; eczema to the dermis).

Allergy - Late-phase response

After the chemical mediators of the acute response subside, late phase responses can often occur. This is due to the migration of other leukocytes such as neutrophils, lymphocytes, eosinophils and macrophages to the initial site. The reaction is usually seen 4-6 hours after the original reaction and can last from 1-2 days. Cytokines from mast cells may also play a role in the persitence of long-term effects. Late phase responses seen in asthma are slightly different to those seen in other allergic responses.