What is atopy? Sidestepping semantics

Atopy may be viewed as the manifestation of a still-undefined defect. It is characterized by certain clinical findings and frequently by derangements of the immune and autonomic nervous systems. The atopic diseases are a group of seemingly unrelated conditions--eczema, asthma, rhinitis, and perhaps hypertrophic sinusitis, vernal conjunctivitis, and migraine--which cluster in individuals and families. In the respiratory tract and eye, eosinophils in tissues and secretions are characteristic and are not dependent on the presence of immediate hypersensitivity. Symptoms suggestive of mast-cell mediator release are common to all the atopic diseases, and there is some evidence that nonimmunologic mediator release is enhanced in atopic patients. In the most clearly defined atopic diseases, eczema and asthma, approximately 80% of patients have increased IgE responses to normal environmental allergens. Accompanying and perhaps underlying the enhanced IgE responses are deficiencies of T cell numbers and function, particularly in suppressor T lymphocytes. Evidence exists that decreased beta 2-adrenergic function and increased cholinergic and alpha-adrenergic responsiveness accompany and perhaps underlie the atopic diseases, whether allergic or nonallergic.