What is the Origin of Neonatal Fc Receptor?

The receptor was initially discovered for its crucial role in the passive transfer of maternal IgG antibodies to the fetus and neonate, providing early immune protection. Subsequent research revealed its critical, lifelong role in maintaining high serum levels of IgG and albumin through a continuous recycling process. The term represents a key physiological mechanism exploited in modern drug design for enhanced pharmacokinetics.

What is the Mechanism of Neonatal Fc Receptor?

The FcRn mechanism involves the internalization of IgG or albumin into the endosome, where the acidic environment facilitates binding to the receptor. The FcRn-bound protein is then recycled back to the cell surface and released into the bloodstream at neutral pH, while unbound proteins are routed for degradation. Therapeutic protein drugs are engineered with an Fc region to hijack this natural recycling pathway, significantly improving their systemic residence time.

Neonatal Fc Receptor ∞ Area

Neonatal Fc Receptor

Meaning

The Neonatal Fc Receptor, or FcRn, is a major histocompatibility complex class I-related receptor expressed on various cell types, including endothelial cells and professional antigen-presenting cells. Its primary physiological role is to protect the Fc region of immunoglobulin G antibodies and serum albumin from rapid lysosomal degradation, effectively extending their half-life in the circulation. In clinical therapeutics, this receptor is strategically leveraged to prolong the activity of protein-based drugs.