Fc gamma receptors and complement system components (FcγR and Complement)

Fc gamma receptors (FcγRs) and complement system components are two distinct but interrelated pillars of the innate and adaptive immune response. FcγRs are a family of cell-surface glycoproteins (including FcγRI, FcγRII, and FcγRIII) that bind the Fc region of IgG antibodies, thereby linking antibody-mediated specificity to effector cell functions such as phagocytosis and antibody-dependent cellular cytotoxicity (ADCC) (Nimmerjahn & Ravetch, 2008, Nat Rev Immunol). The complement system is a complex cascade of over 30 proteins (e.g., C1q, C3, C5) that promotes the clearance of pathogens through opsonization, recruitment of inflammatory cells, and direct lysis via the membrane attack complex (Ricklin et al., 2010, Nat Immunol). In clinical practice, these components are targeted by a variety of therapeutics: complement inhibitors like eculizumab and pegcetacoplan are used to treat paroxysmal nocturnal hemoglobinuria and other complement-mediated diseases, while monoclonal antibodies in oncology are often engineered to enhance their interaction with FcγRs to improve tumor cell killing (Gessner et al., 2012, Ann Hematol). Because this entry encompasses multiple protein families and distinct biological pathways, it is considered a broad functional category rather than a single molecular target. Monitoring these systems often involves measuring complement protein levels (C3, C4) or assessing FcγR genetic polymorphisms that influence drug efficacy (Bournazos & Ravetch, 2017, Cell). Safety concerns for complement inhibitors notably include a significantly increased risk of life-threatening infections by encapsulated bacteria, such as Neisseria meningitidis (FDA, Soliris Prescribing Information).

Other names

Fc-gamma receptorsComplement cascadeEffector system componentsIgG receptorsComplement proteins

Modulation of immune effector functions through binding to Fc receptors on leukocytes or inhibition of the complement protein cascade to prevent cell lysis and inflammation.