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Home , MHC class I, Neonatal Fc receptor

RESEARCH HIGHLIGHTS

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ANTIBODY RESPONSES FcRn — not just for the kids

IgG is the predominant antibody expressing human uterine cell line, bidirectional transport of IgG across isotype found in the female genital the authors showed that IgG could genital tract epithelium. tract and serves as an important be transported in both luminal and Finally, Zili et al. explored defence mechanism against genital abluminal directions by these cells. whether this transport function of tract infections. In a recent study, However, transport of IgG was not FcRn has implications for immune Zili et al. have shown that the observed following FcRn knock- protection in the genital tract. neonatal Fc receptor (FcRn), which down, and chicken IgY (which is Strikingly, the systemic delivery of is crucial for delivering protective structurally similar to IgG but does IgG specific for herpes simplex virus maternal antibodies to the fetus and not bind FcRn) was not transported type 2 (HSV‑2) protected wild-type newborns, also delivers IgG to the across the cell monolayers. but not FcRn-deficient mice from a female genital tract and promotes Next, the authors switched to a lethal intravaginal HSV‑2 infection. protective immunity at this site. mouse system to explore the in vivo These data suggest that IgG It is well appreciated that FcRn functions of FcRn in the genital tract. transfer to the genital tract is not functions in adults to maintain Notably, significantly higher levels of simply passive, as historically serum levels of IgG. Therefore, IgG were found in vaginal washings thought, but involves active transport the authors hypothesized that from wild-type mice than in vaginal by FcRn. This study has important IgG transfer FcRn might also contribute to the washings from FcRn-deficient ani- implications for the development of to the genital transport of IgG across the genital mals. Furthermore, in experiments vaccines, as it suggests that boosting tract is epithelium. Initial screens showed using labelled antibody, systemically systemic or local IgG responses could that mRNA encoding FcRn could delivered IgG could be subsequently contribute to immune protection in not simply be detected in human female genital detected in vaginal washings from the genital tract. passive … but epithelial cell lines, and subsequent wild-type but not FcRn-deficient Yvonne Bordon involves active immunostaining experiments using mice. Labelled IgG delivered by tissue sections confirmed that an intravaginal route was also ORIGINAL RESEARCH PAPER Zili, L. et al. transport Transfer of IgG in the female genital tract by FcRn is expressed at high levels by subsequently detected in the serum MHC class I-related neonatal Fc receptor (FcRn) by FcRn uterine and vaginal epithelial cells of wild-type but not FcRn-deficient confers protective immunity to vaginal infection. in both humans and mice. Using cell mice, supporting the authors’ in vitro Proc. Natl Acad. Sci. USA 28 Feb 2011 (doi:10.1073/pnas.1012861108) monolayers prepared from an FcRn- observations that FcRn can promote