Fc gamma receptors and complement component C1q (FcγR/C1q)

Fc gamma receptors and complement component C1q refers to the primary molecular entities that interact with the Fc (fragment crystallizable) region of immunoglobulin G (IgG) to mediate immune effector functions. Fc gamma receptors (FcγRs) are a family of cell-surface glycoproteins, including FcγRI (CD64), FcγRII (CD32), and FcγRIII (CD16), expressed on various immune cells such as natural killer (NK) cells and macrophages (ibr-inc.com). These receptors trigger antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) upon binding to antibody-coated targets. Complement component C1q is the initiating protein of the classical complement pathway, which binds to the Fc region of IgG or IgM to induce complement-dependent cytotoxicity (CDC) through the formation of the membrane attack complex (PubMed). In therapeutic drug development, this system is a critical target for antibody engineering; oncology treatments like rituximab and obinutuzumab are designed to engage these components to maximize tumor cell killing (Oncogene, 2003). Conversely, antibodies intended for simple ligand neutralization, such as the anti-CGRP migraine therapies galcanezumab and fremanezumab, are often engineered with modified Fc regions to reduce affinity for FcγRs and C1q, thereby minimizing the risk of unwanted inflammatory responses and improving safety (peptideinsight.com).

Other names

Fc effector systemIgG effector targetsFc-gamma receptors and C1qFc effector componentsFc-mediated effector system

Engagement of Fc gamma receptors on immune effector cells to trigger ADCC and ADCP, and binding to C1q to initiate the classical complement pathway and CDC.