In humans, type I FcγRs are classified based on the signalling motifs of their intracellular domains. Activating FcγRs include FcγRI, FcγRIIa, FcγRIIc and FcγRIIIa, which contain immunoreceptor tyrosine activating motifs (ITAM)s. FcγRs are differentially expressed on the surface of lymphoid and myeloid cells and modulated by proinflammatory cytokines, for example, FcγRIIA is expressed on the surface of neutrophils, macrophages and monocytes but FcγRIIC is not. IgG Immune complexes are known to activate type I FcγRIIA/C receptors after binding, leading to a rise in calcium levels and an activation of downstream signalling cascades including ERK, p38 and JNK. These signalling cascades ultimately lead to phagocytosis, cytokine secretion, apoptosis or other numerous active immune responses including upregulating of B cell production. Monomeric IgG is present at high levels in the serum, therefore FcγRIIA/C has low affinity for IgG to prevent monomeric IgG binding and non-specific activation. Mutations/polymorphisms of FcγRIIA/C are associated with autoimmune conditions and increased susceptibility for Kawasaki’s disease or an IVIg anaphylactic reaction. It is also linked to a decreased vaccine efficacy for HIV.

Antibody treatments are a key area of research for cancers as a checkpoint therapy. Inhibition of activatory FcγR like FcγRIIA/C could also block development of inflammatory diseases. In mice models, small ligand analogues for FcγRIIA inhibit macrophage TNF secretion plus platelet activation while also halt the development and progression of collagen-induced arthritis (CIA). Understanding the FcγRIIA/C roles with greater clarity will enhance the progress of anti-inflammatory agents to aid autoimmune conditions. This antibody could be a useful research tool for the development of novel immunotherapeutic approaches.