36,41 Therefore, while intracellular bacterial pathogens like Lis

36,41 Therefore, while intracellular bacterial pathogens like Listeria and Salmonella are capable of in utero fetal invasion,39,42,43 infection susceptibility during pregnancy is not simply the result of the presence of fetal tissue that is susceptible to direct invasion, and instead more likely reflects systemic defects in host defence dictated by expanded maternal Treg cells. These findings with experimental Listeria

infection in mice are also consistent with the epidemiological features of this infection in humans where a significant portion of disseminated maternal infection www.selleckchem.com/products/Y-27632.html cases occur without evidence of fetal direct invasion.38 Hence, the physiological

expansion of maternal Foxp3+ Treg cells during pregnancy compromises host defence, and these immune defects are exploited by pathogens like Listeria and Salmonella with a predisposition for prenatal infection. Importantly, since the expansion of maternal Treg cells is blunted during syngeneic check details pregnancy, where the only potential sources of antigen heterogeneity between maternal and fetal antigens are those encoded on the Y chromosome, the importance of expanded maternal Treg cells in host defence for other prenatal pathogens may have been overlooked in previous studies, and deserve re-investigation using allogeneic pregnancy. The impacts on host defence dictated by the physiological expansion

of immune suppressive Treg cells also have broader implications beyond this instance of prenatal infection susceptibility. For example, the progressive expansion of Treg cells among peripheral CD4+ T cells occurs with aging throughout the lifespan of humans and mice.44–47 In particular, individuals over 60 years have a threefold increased proportion of Treg cells compared with Bacterial neuraminidase individuals less than 40 years.44,45 In turn, when pregnancy-associated cases are excluded, individuals over 60 years are also markedly more susceptible to disseminated Listeria infection compared with those < 60 years.48 Reciprocally following natural West Nile virus infection, symptomatic infection is more common in younger than older individuals, and these findings are consistent with the protective role provided by Treg cells in this infection.23,49 However, the expansion of Treg cells with aging alone does not explain other epidemiological data for this infection where individuals over 70 years compared with those aged 20–69 years have fivefold increased mortality with West Nile virus infection.

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