Characterization and localization of the neonatal Fc receptor in adult human kidney

The binding of Fc fragments of Ig on glomerular epithelial cells (GEC) was observed previously, but the receptor could not be identified. In immunoflu orescence and immunohistochemical studies using normal adult human kidney s ections, the presence of the so-called neonatal Fc receptor (FcRn) was demo nstrated on GEC as well as in the brush border of proximal tubular cells. F cRn transcripts were also detected on isolated glomeruli by reverse transcr iption-PCR. Using an immortalized GEC line, the presence of the FcRn was co nfirmed by flow cytometry, reverse transcription-PCR, Western blotting, and by the pH dependence of the binding of heat-aggregated IgG. Because it is well established that the FcRn is involved in IgG transcytosis, it is hypot hesized that the FcRn in the kidney may play a role in the reabsorption of IgG. Ongoing studies should clarify the role of the FcRn as a potential tar get for immune complexes on GEC and should assess its relevance in physiolo gy and pathology.