The evolution of IgE
- report from the 2nd European Congress of Immunology held in Berlin


IgE is an evolutionary conserved member of the immunoglobulin (Ig) family (antibodies, which play a key function in immune response). Compared to all other immunoglobulins there are only minute amounts of IgE in blood serum (nano- to micrograms per ml range) of normal healthy individuals and of normal laboratory mouse strains.

IgE is most evident in the cells in the skin both outside and inside the body (linings of the gut, stomach, mouth, nose etc) where it can remain for weeks to months whereas in the blood in only lasts for hours. This suggests, say the redsearchers, that IgE plays a role in local immune defence mechanisms.

However, the core function for IgE is still unknown. From an evolutionary point of view, IgE can be found in all mammalia. It therefore originated at least 160 million years ago, possibly even more than 300 million years ago, from a gene duplication of IgY which gave rise to IgE and IgG, respectively. IgG cells are now occupied in recognising and labelling allergens to enable scavenger cells to find and destroy them while IgE is responsible for anaphylactic activities, which represent another way of immune defense, which may involve the whole body.

In these days IgE is best known for its strong, unwanted initiation of allergic reactions. These can range from annoying, local symptoms, like hay fever, to life-threatening, systemic reactions like anaphylactic shock.

Remarkably, over the last four decades the incidence of allergic disease has risen. This represents an intriguing problem from a medical, epidemiological, immunological, genetic and evolutionary view. Unfortunately, it is also a major socio-economic problem.

The interpretation of the these data by the author of the report, Gernot Achatz, of the department of Molekular Biology, University of Salzburg, is that control mechanisms, that were adequate in the past and honed in evolution, are failing. In the recent past he and others have described several B cell specific control mechanisms that indicate a tight control of the IgE response. The understanding of these mechanisms, combined with the analysis of the biological function of the IgE molecule during an immune response are the prerequisite for the establishment of new systemic IgE targeted therapeutic strategies in the future.

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First published in 2009

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