ReceptorFc

ReceptorFc, more commonly referred to as Fc receptors (FcRs), are a family of cell-surface proteins that bind the Fc region of immunoglobulins. By recognizing antibodies that have engaged their antigens, Fc receptors translate humoral immune responses into cellular actions, including phagocytosis, cytotoxicity, cytokine release, and antigen presentation. They play roles in host defense, immune regulation, and inflammatory processes.

Fc receptors bind different antibody isotypes with varying affinity. In humans, Fc gamma receptors for IgG (FcγRs) are widely distributed on natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, and some B cells. Key members include FcγRI (CD64) with high affinity, FcγRII (CD32) with several isoforms (IIA, IIB, IIC), and FcγRIII (CD16) with activating forms. Other Fc receptors include FcεRI for IgE on mast cells and basophils, FcαRI (CD89) for IgA, and FcμR for IgM. Receptors often signal through immunoreceptor tyrosine-based activation motifs (ITAMs) or inhibitory motifs (ITIMs), balancing activation and restraint.

Mechanistically, activating Fc receptors trigger phagocytosis, antibody-dependent cellular cytotoxicity (ADCC), and inflammatory cytokine production, whereas inhibitory receptors, such as FcγRIIb, suppress excessive activation to limit tissue damage. ReceptorFc signaling is influenced by receptor expression patterns, immune complex size, and glycosylation of the antibody Fc region.

Clinical relevance includes genetic polymorphisms that affect Fc receptor affinity and function, impacting infection susceptibility, autoimmune risk, and responses to monoclonal antibody therapies. Therapeutic antibodies can be engineered to modulate Fc receptor engagement to enhance or reduce effector functions, tailoring treatment outcomes.