Soluble circulating Fc gamma receptors in human serum. A new ELISA assay for specific and quantitative detection.

We have developed a simple, rapid, and sensitive enzyme-linked immunoadsorbent assay (ELISA) to measure soluble cell-free human Fc gamma receptor (Fc gamma R) in serum. This assay is based on the use of two monoclonal antibodies directed against different epitopes expressed on the same low avidity human Fc gamma R (CD16), which is present on polymorphonuclear leukocytes, macrophages and NK cells. This sandwich ELISA, which can measure 2 nM concentration of Fc gamma R, has enabled us to demonstrate the presence and to measure the level of soluble cell-free human Fc gamma R (CfH-Fc gamma R) in normal human serum.