Fc region of therapeutic antibodies bound to tumor antigens (Fc region)

The Fc (fragment crystallizable) region of therapeutic antibodies serves as a critical bridge between adaptive and innate immunity when bound to tumor-associated antigens. Once the antibody's Fab domains recognize and bind to specific markers on a cancer cell, the Fc region undergoes conformational changes or clustering that allows it to be recognized by Fc-gamma receptors (FcγRs) on effector cells like Natural Killer (NK) cells and macrophages (Wang et al., 2018, Nature Reviews Drug Discovery). This interaction triggers potent anti-tumor mechanisms, including antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Additionally, the Fc region can bind to the C1q component of the complement system, initiating complement-dependent cytotoxicity (CDC) to pore-form and lyse the target cell (Quast et al., 2015, Methods). In modern oncology, the Fc region is frequently engineered—through glycan modification (afucosylation) or amino acid substitutions—to enhance its affinity for activating receptors like CD16a, thereby boosting the clinical efficacy of monoclonal antibodies (Nimmerjahn & Ravetch, 2008, Nature Reviews Immunology). The therapeutic success of these antibodies often depends on the patient's FcγR genetic polymorphisms, such as the FCGR3A-V158F variant, which influence the strength of the immune response against the tumor (Cartron et al., 2002, Blood). Beyond cell killing, the Fc region also interacts with the neonatal Fc receptor (FcRn) to regulate the half-life and recycling of the antibody within the circulation. Consequently, the Fc region is not merely a structural component but a functional target for optimizing the therapeutic window and potency of cancer immunotherapies.

Other names

Fragment crystallizable regionIgG Fc domainAntibody Fc tailFcγ receptor ligandEffector domain of IgG

Recruitment and activation of immune effector cells (NK cells, macrophages, neutrophils) via Fc-gamma receptor (FcγR) engagement and activation of the classical complement pathway via C1q binding to induce tumor cell lysis.