Soluble Fcγ Receptors: Interaction with Ligands and Biological Consequences

Soluble Fcγ receptors are produced by cleavage of the membrane receptors or by alternative splicing. They are found in biologic fluids. After a brief description of the structure and mode of production of soluble FcγR, we address the question of ligands and function of the soluble FcγR by using recombinant molecules and transgenic animals. We show that soluble FcγR are not only IgG-binding factors which interfere with, and block, Fc-dependent immune reactions but also molecules that interact, in vitro, with non-Ig-ligands such as CR3 and CR4 and are trigger or regulate immune functions via these receptors.