Activating Fc gamma receptors (FcγR) (FcγR)

Activating Fc gamma receptors (FcγRs) are a group of cell-surface glycoproteins that bind the Fc region of immunoglobulin G (IgG) antibodies to initiate stimulatory immune responses [1.1.1, 1.2.1]. In humans, this group includes the high-affinity receptor FcγRI (CD64) and the low-to-medium affinity receptors FcγRIIa (CD32a), FcγRIIc (CD32c), FcγRIIIa (CD16a), and FcγRIIIb (CD16b) [1.1.2, 1.2.4]. These receptors are widely expressed on leukocytes, including natural killer (NK) cells, macrophages, monocytes, neutrophils, and dendritic cells [1.2.2, 1.4.2]. Upon engagement by IgG-coated targets or immune complexes, activating FcγRs signal through immunoreceptor tyrosine-based activation motifs (ITAMs) to trigger critical effector functions such as antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and the release of pro-inflammatory cytokines [1.1.2, 1.3.3, 1.4.4]. They play a dual role in clinical medicine: they are the primary mediators of the therapeutic efficacy of anti-cancer monoclonal antibodies, yet their dysregulation is a key driver of tissue damage in autoimmune diseases like systemic lupus erythematosus [1.2.3, 1.3.2, 1.4.2]. Consequently, they are major targets for drug development, with strategies ranging from Fc-engineering to enhance anti-tumor activity to the use of small-molecule inhibitors that block their downstream signaling [1.2.2, 1.3.1, 1.3.5].

Other names

Fc gamma receptorsFc-gamma receptorsCD64 (FcγRI)CD32a (FcγRIIa)CD32c (FcγRIIc)CD16a (FcγRIIIa)CD16b (FcγRIIIb)ITAM-bearing Fc receptorsStimulatory Fc gamma receptors

Activation of immune effector functions (ADCC, ADCP) via Fc-receptor engagement; competitive inhibition of immune complex binding; modulation of the activating-to-inhibitory (A/I) receptor ratio; inhibition of downstream ITAM signaling pathways.