The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.

DEFINITION:

type 1 hypersensitivity reaction

This allergic reaction is also called immediate or anaphylactic hypersensitivity. After a first exposure to an antigen (which may be a harmless substance such as grass pollen), antibodies (substances that can recognize and bind to the antigen) are formed; these antibodies coat cells called mast cells in various tissues. On second exposure, the antigen and antibodies combine, causing the mast cells to disintegrate and release various chemicals that cause the symptoms of asthma, allergic rhinitis (hay fever), urticaria (hives), anaphylactic shock, or other illnesses of an allergic nature.