Soluble IgE receptors-Elements of the IgE network

Soluble isoforms of three human IgE Fc receptors, namely Fc epsilon RI, FceRII, and galectin-3, can be found in serum. These soluble IgE receptors are a diverse family of proteins unified by the characteristic of interacting with IgE in the extracellular matrix. A truncated form of the alpha-chain of FceRI, the high affinity IgE receptor, has recently been described as a soluble isoform (sEc epsilon R1). Multiple soluble isoforms of CD23 (5CD23), the low affinity IgE receptor also known as Fc epsilon RII, are generated via different mechanisms of extracellular and intracellular proteolysis. The second low affinity IgE receptor, galectin-3, only exists as a secretory protein. We here discuss the physiological roles of these three soluble IgE receptors as elements of the human IgE network Additionally, we review the potential and current use of sEc epsilon RI, sCD23, and galectin-3 as biomarkers in human disease. (C) 2011 Elsevier B.V. All rights reserved.