Abnormal immune cells may cause unprovoked a...( Two new clinical reports shed light ...),Health

Two new clinical reports shed light on why some people suffer from recurrent episodes of idiopathic anaphylaxis--a potentially life-threatening condition of unknown cause characterized by a drop in blood pressure, fainting episodes, difficulty in breathing, and wheezing.

In some of these individuals, researchers have found mast cells (a type of immune cell involved in allergic reactions) that have a mutated cell surface receptor that disturbs normal processes within the cell. Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), say the association of this mutation with unprovoked anaphylaxis is striking. The hope is that these individuals may respond to inhibitors targeting the mutated cell surface receptor.

While some people suffer anaphylaxis as part of a serious allergic reaction, in two out of three people, anaphylaxis has no known cause and thus the anaphylactic reaction is called idiopathic.

Anaphylaxis occurs when mast cells release large quantities of chemicals (histamines, prostaglandins and leukotrienes) that cause blood vessels to leak, bronchial tissues to swell and blood pressure to drop. Resulting conditions such as shock and unconsciousness usually resolve in most people treated with epinephrine (adrenaline) and first aid measures. In rare cases, however, death may occur.

Abnormally low blood pressure and fainting episodes are also features of mastocytosis--a disease in which people have an excessive number of mast cells. Several years ago, Dean Metcalfe, M.D., chief of the Laboratory of Allergic Diseases at NIAID, Cem Akin, M.D., Ph.D., and their NIAID colleagues decided to find out whether idiopathic anaphylaxis might have a genetic trigger related to that seen in mastocytosis. It is known that systemic mastocytosis in adults often results from a mutation in the Kit receptor found on the surface of mast cells, a discove
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