The Immunologic Functions of the Neonatal Fc Receptor for IgG
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Careful regulation of the body’s immunoglobulin G (IgG) and albumin concentrations is necessitated by the importance of their respective functions. As such, the neonatal Fc receptor (FcRn), as a single receptor, is capable of regulating both of these molecules and has become an important focus of investigation. In addition to these essential protection functions, FcRn possesses a number of other functions that are equally as critical and are increasingly coming to attention. During the very first stages of life, FcRn mediates the passive transfer of IgG from mother to offspring both before and after birth. In the adult, FcRn regulates the persistence of both IgG and albumin in the serum as well as the movement of IgG, and any bound cargo, between different compartments of the body via transcytosis across polarized cells. FcRn is also expressed by hematopoietic cells; consistent with this, FcRn regulates MHC class II presentation and MHC class I cross-presentation by dendritic cells. As such, FcRn plays an important role in immune surveillance throughout adult life. The increasing appreciation for FcRn in both homeostatic and pathological conditions is generating an intense interest in the potential for therapeutic modulation of FcRn binding to IgG and albumin.
KeywordsNeonatal Fc receptor FcRn Maternal IgG transcytosis
We apologize to all of our colleagues we have not cited due to space limitations. Timo Rath receives support from the German Research Foundation Grant no. RA 2040/1-1. Timothy Kuo was supported by NIH DK071798. Kristi Baker was supported by The Canadian Institutes for Health Research. Masaru Yoshida receives support from the Global COE Program, Global Center of Excellence for Education and Research on Signal Transduction Medicine in the Coming Generation and Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (JSPS). Derry Roopenian is supported by NIH CA034196 and AR054407. Edda Fiebiger is supported by the NIH AI075037. Wayne Lencer is supported by NIH DK48106, DK084424, DK090603 and Harvard Digestive Diseases Center (NIH P30DK034854). Richard Blumberg is supported by NIH DK44319, DK51362, DK53056, DK88199 and Harvard Digestive Diseases Center (NIH P30DK034854).
Conflict of Interest
The authors declare that they have no conflict of interest.
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