Neonatal Fc receptor for immunoglobulin G (FcRn) (FcRn)

The neonatal Fc receptor (FcRn) is an MHC class I-related molecule consisting of a membrane-bound heavy chain noncovalently associated with β2-microglobulin.[10] Originally characterized for its role in transporting immunoglobulin G across polarized epithelial cells and protecting IgG from degradation, FcRn has emerged as an important regulator of the adaptive immune response.[10] FcRn is functionally expressed in immune cells including monocytes, macrophages, and dendritic cells, where it plays a pivotal role in linking cellular and humoral immunity through regulation of immune complex internalization, antigen presentation, and inflammatory cascade control.[10] As an MHC-related receptor, FcRn shares structural homology with classical MHC class I molecules but serves distinct functions in immunoglobulin homeostasis and immune regulation. Therapeutic interest in FcRn is growing, particularly for modulating autoimmune responses and optimizing immune function in infection and cancer contexts, though clinical applications remain largely investigational.

Other names

MHC class I-related neonatal Fc receptorFc receptor, neonatalFCGRT (gene name)

Binds IgG in a pH-dependent manner to facilitate transport[10] Associates noncovalently with β2-microglobulin[10] Structurally similar to MHC class I, consisting of a membrane-bound heavy chain complexed with β2-microglobulin[10]