Low affinity immunoglobulin gamma Fc receptor III-A (FcγRIIIa) (FcγRIIIa)

Low affinity immunoglobulin gamma Fc receptor III-A (FcγRIIIa), also known as CD16a, is a transmembrane glycoprotein expressed primarily on natural killer (NK) cells, macrophages, and monocytes (UniProt: P08637). It serves as a key mediator of antibody-dependent cellular cytotoxicity (ADCC), a process where effector cells recognize and kill target cells coated with IgG antibodies (PubMed: 25323929). In the context of odesivimab, a component of the Inmazeb cocktail used to treat Zaire ebolavirus, the antibody's Fc region binds to FcγRIIIa to recruit immune effector cells to the site of infection (FDA: Inmazeb Prescribing Information). This interaction triggers the release of cytotoxic mediators like perforin and granzymes, leading to the destruction of virus-infected cells and enhancing viral clearance (PubMed: 33053271). The efficacy of this mechanism can be influenced by genetic polymorphisms in the FCGR3A gene, particularly the V158F variant, which alters the receptor's affinity for IgG1 antibodies (PubMed: 15569832). Consequently, FcγRIIIa is a vital component in the mechanism of action for many monoclonal antibody therapies used in infectious diseases and oncology. Beyond ADCC, the receptor also contributes to the production of inflammatory cytokines and the clearance of immune complexes. Therapeutic strategies often involve engineering the Fc region of antibodies to increase their affinity for FcγRIIIa, thereby boosting the immune response against pathogens or tumors.

Other names

CD16aFCGR3AFc-gamma RIIIaCD16A antigenLow affinity IIIa receptor for the Fc fragment of IgGFCGR3

The Fc region of odesivimab binds to FcγRIIIa on effector cells (e.g., NK cells), triggering antibody-dependent cellular cytotoxicity (ADCC) to eliminate Ebola virus-infected cells.