FcRIreseptoriin

FcRIreseptoriin, also known simply as the high‑affinity FcγRI, is a transmembrane glycoprotein that belongs to the Fc receptor family. It binds the constant (Fc) region of immunoglobulin G (IgG) with high affinity, allowing it to mediate antibody‑dependent cellular cytotoxicity (ADCC), phagocytosis, and release of inflammatory mediators.

The receptor is encoded by the FCGR1A gene in humans and is expressed predominantly on macrophages, monocytes, and dendritic cells. Structurally, FcRIreseptoriin comprises a single extracellular Ig‑like domain that extends to a short cytoplasmic tail; the signalling function is provided by a non‑canonical immunoreceptor tyrosine‑based activation motif (ITAM) within the associated γ‑chain. Upon IgG engagement, the ITAM is phosphorylated, recruiting Syk kinase and initiating downstream signaling cascades that result in cytokine production and activation of the cell’s effector functions.

In addition to its role in innate immunity, FcRIreseptoriin participates in the clearance of immune complexes and helps regulate systemic IgG levels. Alterations in its expression or genetic variants have been linked to autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and certain forms of inflammatory bowel disease. Polymorphisms in the FCGR1A promoter region can affect receptor expression and influence susceptibility to infections with encapsulated bacteria.

The receptor’s high affinity for IgG has made it a target for therapeutics that aim to modulate immune complex clearance or inhibit adverse antibody‐mediated responses. FcRIreseptoriin is also exploited in biotechnological applications such as the purification of IgG antibodies using Fc receptor affinity chromatography.