Abstract
Purpose:
The neonatal Fc receptor (FcRn) plays a critical role in the homeostasis and degradation of immunoglobulin G (IgG) by regulating its transport across epithelial and endothelial cells by recycling FcRn-bound IgG back onto the apical cell surface and into the blood stream. This recycling is mediated by the binding of FcRn to the Fc domain of IgG. FcRn expressed in the eye may therefore affect the distribution and half-life of intravitreally injected anti-VEGF molecules containing IgG-Fc domains. In order to establish whether FcRn-Fc(IgG) interactions may occur in the eye, we studied the transcription, expression and distribution of FcRn in postmortem ocular tissue.
Methods:
We used qPCR to study mRNA expression of the transmembrane chain of FcRn (FCGRT) in retina, optic nerve, retinal pigment epithelium (RPE)/choroid plexus, ciliary body/iris plexus, lens, cornea and conjunctiva isolated from mouse, rat, pig and human postmortem eyes and used immunohistochemistry (IHC) to establish the distribution of FCGRT in mouse and human eyes.
Results:
We found in all four tested species FCGRT mRNA transcription in the retina, RPE/choroid/ and the ciliary body/iris, while IHC showed FCGRT expression in the retinal and choroidal vasculature and in the ciliary body epithelium. Weak staining was also detected in the RPE.
Conclusions:
Our results demonstrate that FcRn has the potential to interact with IgG-Fc domains in the ciliary epithelium, retinal and choroidal vasculature and the RPE, which might affect the half-life and distribution of intravitreally injected Fc-carrying molecules.
Keywords: 472 comparative anatomy •
674 receptors •
554 immunohistochemistry