Allergy.

A state of immunologically mediated hypersensitivity to a foreign material.

Anaphylaxis.

A systemic, immunologically mediated hypersensitivity reaction to a foreign substance. Clinical manifestations are cutaneous, respiratory, and cardiovascular with shock and laryngeal edema as important causes of death when a fatality occurs.

Antibody.

A protein molecule formed by the immune system in response to the body's contact with an antigen, having the specific capacity of neutralizing the antigen and creating immunity against certain microorganisms and toxicants. Certain antibodies can cause adverse hypersensitivity (allergic) reactions.

Antigen.

A substance that stimulates the production of an antibody when introduced into the body. Antigens are usually high-molecular-weight compounds, such as proteins. However, low-molecular-weight compounds (e.g., drugs or industrial chemicals) can bind to serum proteins and become antigenic.

Asthma.

A usually chronic condition characterized by intermittent episodes of wheezing, coughing, and difficulty in breathing, sometimes caused by an allergy to inhaled substances.

Atopen.

The exciting cause of any form of atopy.

Atopy.

The state of having one or more of a defined group of diseases—allergic rhinoconjunctivitis, allergic asthma, and atopic dermatitis—that are caused by a genetic propensity to produce IgE antibodies to environmental allergens encountered through inhalation, ingestion, and, possibly, skin contact. A broader definition, sometimes used for epidemiologic studies, requires only the presence of IgE antibody, regardless of allergic disease.

Autoantibody.

An antibody that reacts with a component of the tissues of the animal making the antibody.

Autoimmunity.

A condition resulting from the production of autoantibodies, characterized by cell-mediated or humoral immunologic responses to antigens of one's own body, sometimes with damage to normal components of the body.

B

B cell.

A type of lymphocyte that produces antibodies and originates in bone marrow.

Bioaerosol.

An aerosol containing living organisms or particles derived from living organisms.

Bronchoalveolar lavage fluid.

The fluid obtained from the lungs by lavage. Lavage is a technique in which an organ is flushed with water to allow analysis of material in the drainage fluid (in this case, cells from the bronchioles and alveoli).



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