SELECTED ARTICLES FROM THE RECENT LITERATURE 2005
12/5/05
How important are autoantibodies to the high affinity IgE receptor in chronic urticaria?
Summary
Background - In 80-90% of individuals with chronic urticaria (lasting continuously over at least 6 weeks), no external cause has been found. Such cases are called chronic idiopathic urticaria (CIU). Current evidence points to a possible auto-immune pathogenesis of CIU.
Findings - This subject was reviewed by Sheikh of the Harvard Medical School. He pointed out antibodies against the alpha chain of the high affinity IgE receptor (Fc epsilon RI) are present in the sera of 30-50% of CIU patients. This antibody can induce release of mediators in vitro from basophils and mast cells expressing the Fc epsilon RI on their surface. Indirect evidence suggests that these antibodies are functional in vivo but this evidence is not yet conclusive. In the remaining 50-60% CIU patients without demonstrated anti-Fc epsilon RI antibodies, the pathogenesis is less clear although the basophils and mast cells may have intrinsic abnormalities.
Reference
Curr Opin Allergy Clin Immunol 2005;5:403-7
Editor's Comments
This review covers much of the interesting recent findings in this area. Some other aspects are worthy of mention: 1) anti-Fc epsilon RI antibodies (as detected by ELISA) have been found in sera of patients with some other skin diseases (e.g. dermatomyositis) but such antibodies do not induce mediator release from basophils; 2) in a small percentage (5-10%) of CIU cases, the serum contains antibodies against IgE itself; 3) complement binding may enhance the histamine-releasing activity of the anti-Fc epsilon RI antibodies in some CIU sera although serum complement C3 and C4 levels are typically normal in CIU; 4) one of the strongest lines of evidence for in vivo activities of these antibodies is the dramatic reduction in CIU manifestations in some patients following plasmapharesis. This improvement lasts about 3 weeks with recurrence of skin manifestations at the time serum anti-Fc epsilon RI antibody levels return to pre-pharesis levels.
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