The structure of Fc receptor/Ig complexes: considerations on stoichiometry and potential inhibitors.

Recently, Fc receptors for immunoglobulins moved further into the focus of pure and applied research as a role in the induction and development of autoimmune diseases and allergies is becoming more probable. Indeed by connecting the humoral with the cellular immune response FcRs possess an important role in the immune system in which the initial, crucial step is the binding of an immunoglobulin to the cell bound receptor. Thereafter a variety of effector functions depending on the cell and the receptor is triggered. This key event could recently be visualised with the solution of the crystal structure of a human Fc receptor in complex with its native ligand the Fc fragment of IgG1. In this paper the reasons for a 1:1 stoichiometry between Fc receptor and Fc Fragment and the medical applications of potential inhibitors of complex formation are highlighted.