Hypersensitivity diseases

Diseases or ailments caused by impaired immune responses are called hypersensitivity disorders.

35.1 Causes of hypersensitivity diseases

Autoimmunity

Reactions against microbes

Reactions against environmental antigens

 

Autoimmunity

It may be defined as the failure of normal process of an individual to distinguish between self and non-self i.e when the individual fails to recognize its own parts as self and develops an immune response against its own cells and tissues. Diseases that occur because of autoimmunity are called as autoimmune diseases.

Reactions against microbes

Reactions against persistent microbial agent may occur in the form of T-cell response. Tuberculosis, inflammatory bowel disease and viral hepatitis are some of the related conditions.

Reactions against environmental antigens

It does not occur in majority of the population but very less percentage of the individuals may show reaction against some harmless environmental products. As a result of allergy such patients generate immunoglobulin E (IgE) antibodies that cause allergic reactions or disease.