Activating and inhibitory Fcγ receptors in rheumatoid arthritis: from treatment to targeted therapies

Fc gamma receptors (Fc gammaRs) bind the constant Fc region of IgG molecules. IgG/antigen-containing immune complexes elicit a variety of effector functions in cells that express activating Fc gammaRs. Because activating Fc gammaRs are present on cells from the innate immune system, such as dendritic cells, monocytes/macrophages and granulocytes, these IgG receptors form a crucial link between the innate and the acquired immune systems. Recently, the ability to detect the inhibitory Fc gammaRIIb on cells has indicated an imbalance between activating and inhibitory Fc gammaRs in rheumatoid arthritis. This progress offers an opportunity to study modulation of Fc gammaR balance and could stimulate development of Fc gammaR-directed immunotherapy.