Neonatal Fc receptor (FcRn) or Fc gamma receptor (FcRn (for neonatal Fc receptor), FcγR (for Fc gamma receptors, e.g., FcγRI, II, III))

"Fc receptor blockade" refers broadly to therapeutic strategies that inhibit one or more members of the family of cell-surface proteins known as Fc receptors, which bind the constant region ("fragment crystallizable," or "Fc") portion of immunoglobulins. The most clinically relevant targets are: 1. Neonatal fc Receptor (FcRn): This is a key regulator responsible for protecting immunoglobulin G (IgG) from lysosomal degradation by recycling it back into circulation. Blocking this pathway reduces overall levels—and especially pathogenic forms—of circulating IgGs implicated in many autoimmune diseases such as myasthenia gravis. Several drugs now approved target this mechanism directly by binding/blocking the interaction between endogenous antibodies and their recycling machinery at cellular surfaces. 2. Classical Activating/Inhibitory Fcgamma Receptors (e.g., CD64, CD32, CD16): These are expressed mainly on leukocytes where they mediate effector functions like phagocytosis, cytotoxicity, cytokine release upon engagement with antibody-coated cells/pathogens. Blockade here can prevent destruction mediated by autoantibody-coated cells—as seen therapeutically in conditions like ITP. However, broad inhibition risks impairing normal host defense mechanisms. In summary: While "fc receptor blockade" is not itself a molecular entity but rather an approach/mechanism involving several possible protein targets—most notably neonatal fc Receptor (FcRn), which has become an important validated drug target—the term should always be mapped specifically when structuring data about drug-target interactions.

Other names

Neonatal Fc receptorIgG receptorFCGRsCD64/FcγRICD32/FcγRIICD16/FcγRIII

Blockade/inhibition of the neonatal or classical IgG-binding site on the respective receptors prevents recycling/prolongation/cellular activation by pathogenic antibodies. For FcRn blockers, this leads to increased degradation and reduced serum levels of total IgG including autoantibodies implicated in disease pathogenesis. For classical activating/inhibitory FcgammaRs, blockade can prevent phagocytosis/ADCC/cell activation by immune complexes.