Fc gamma receptors and complement components (FcγR and Complement)

Fc gamma receptors (FcγRs) and the complement system represent the two major effector pathways of the humoral immune response that bridge innate and adaptive immunity. FcγRs are a family of cell-surface receptors that bind the Fc portion of IgG antibodies, mediating 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 plasma and membrane-bound proteins that enhance the ability of antibodies and phagocytic cells to clear microbes and damaged cells (Ricklin et al., 2010, Nat Immunol). These systems are tightly integrated; for instance, the classical complement pathway is initiated by the binding of C1q to antibody-antigen complexes, which also interact with FcγRs. Dysregulation of these pathways is implicated in various pathologies, including systemic lupus erythematosus, rheumatoid arthritis, and paroxysmal nocturnal hemoglobinuria (Morgan & Harris, 2015, Nat Rev Drug Discov). Therapeutic targeting of the complement system has led to the development of inhibitors like eculizumab (targeting C5) and pegcetacoplan (targeting C3) (Ricklin & Lambris, 2013, J Immunol). Similarly, FcγR pathways are modulated through the use of intravenous immunoglobulin (IVIG) or engineered monoclonal antibodies designed to enhance or inhibit receptor binding (Smith & Clatworthy, 2010, Nat Rev Immunol). Understanding the interplay between these components is essential for developing effective immunotherapies for autoimmune and inflammatory disorders.

Other names

Fc-gamma receptorsComplement systemIgG receptorsComplement cascadeEffector systems

Inhibition of complement protein cleavage (e.g., C3 or C5), blockade of anaphylatoxin receptors (C5aR), and modulation of Fc-gamma receptor signaling or IgG recycling to reduce inflammatory effector functions.