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Allergies and autoimmune diseases

3. Allergies and autoimmune diseases

Agents such as pollen, dust mites, certain  foods etc can act as  antigens and induce an immune response.

  • Allergic diseases such as asthma, eczema, food allergies occur when the body overreacts to antigens (also called allergens) such as pollen, dust mites etc causing inflammatory responses such as sneezing and irritation.
  • Autoimmune diseases such as Type 1 diabetes and multiple sclerosis etc occur when the immune system overreacts against  the body’s own cells and tissues (self antigens).

The process by which the body prevents itself from attacking its own cells  is called  Immune tolerance.

Allergies – asthma, hayfever, food allergy, excema etc

In response to exposure to an antigen such as pollen, dust mites etc,  the allergen binds to the surface of B Lymphocyte cells

T lymphocytes (such as Th2 cells) also bind to the antigen and in so doing activate the B cells to secrete immunoglobulin, IgE. 

IgE, in turn, reacts with Mast cells which release pharmacologically active agents which cause the typical symptoms such as irritation, sneezing, constriction of the airways etc

Autoimmune diseases

Autoimmune diseases such as Type 1 diabetes, inflammatory bowel disease and multiple sclerosis  result from a failure of Immune tolerance mechanisms found in the normal human body

This leads to production of antibodies  or inflammatory agents against the bodies own cells (self antigens) or activation of other types of T helper cells e.g Th17 cells which react with self antigens. 

This leads to the tissue injuries and degradation typical of autoimmune diseases