title: Expression of neonatal Fc receptor in the eye.
abstract: OBJECTIVE
  The neonatal Fc receptor (FcRn) plays a critical role in the homeostasis and degradation of immunoglobulin G (IgG). It mediates the transport of IgG across epithelial cell barriers and recycles IgG in endothelial cells back into the bloodstream. These functions critically depend on the binding of FcRn to the Fc domain of IgG. The half-life and distribution of intravitreally injected anti-VEGF molecules containing IgG-Fc domains might therefore be affected by FcRn expressed in the eye. In order to establish whether FcRn-Fc(IgG) interactions may occur in the eye, we studied the mRNA and protein 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, RPE/choroid plexus, ciliary body/iris plexus, lens, cornea, and conjunctiva isolated from mouse, rat, pig, and human postmortem eyes and used immunohistochemistry to determine the pattern of FcRn expression in FCGRT-transgenic mouse and human eyes.
  
  
  RESULTS
  In all four tested species, Fcgrt mRNA was expressed in the retina, RPE/choroid, and the ciliary body/iris, while immunohistochemistry documented FcRn protein expression in the ciliary body epithelium, macrophages, and endothelial cells in the retinal and choroidal vasculature.
  
  
  CONCLUSIONS
  Our results demonstrate that FcRn has the potential to interact with IgG-Fc domains in the ciliary epithelium and retinal and choroidal vasculature, which might affect the half-life and distribution of intravitreally injected Fc-carrying molecules.
authors.affiliation: UCL Institute of Ophthalmology, University College London, London, United Kingdom.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Powner
authors.forename: Jenny A G
authors.initials: JA
authors.lastname: McKenzie
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Christianson
authors.forename: Derry C
authors.initials: DC
authors.lastname: Roopenian
authors.forename: Marcus
authors.initials: M
authors.lastname: Fruttiger
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D005123:Eye / Q000276:immunology / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D007111:Immunity, Cellular; D007150:Immunohistochemistry; D007231:Infant, Newborn; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D011961:Receptors, Fc / Q000096:biosynthesis / Q000235:genetics*; D013552:Swine
chemical_list: D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger; D011961:Receptors, Fc; C100688:Fc receptor, neonatal
keywords: blood-ocular barrier; ciliary epithelium; drug delivery; macrophages