Definitive evidence that IFN was escaping the uterus was provided by Oliveira et al.75 who demonstrated a 500–1000-fold increase in antiviral activity in the uterine vein compared to the uterine artery or jugular blood of early pregnant ewes. These results provided strong support for the early evidence showing low, but detectable levels of IFN-τ7 and antiviral activity8 in the blood. Work from this same group later demonstrated that the antiviral activity was indeed caused by release of IFN-τ.76

These important studies were the first to definitively selleck screening library demonstrate that IFN-τ had a direct systemic effect, and that this effect could increase CL lifespan. Interestingly, Tuo et al.78 had previously shown

that exogenous IFN-τ had dramatic effects on immune cell recirculation and redistribution in lambs by reducing CD4+, CD5+ and gamma delta + T cells in the peripheral circulation without changing numbers of CD8+ T cells. This effect occurred within 6–12 hr of treatment and peripheral immune cell populations returned to pre-treatment control values by 48 hr. Furthermore, IFN-τ was shown to cause a dose-dependent reduction in lymphocyte proliferation79 and to suppress lymphocyte blastogenesis80in vitro. In contrast, IFN-τ stimulated NK Selleck GSI-IX cell activity in sheep PBMC.81 Taken together, these experiments provide evidence that, while ruminants and humans possess different mechanisms for supporting CL function during early pregnancy, there exists the distinct possibility that they may share functions as a result of the fact that they are both present in the peripheral circulation during the very earliest stages of pregnancy recognition signaling and both can apparently bind and alter function of circulating immune cells. Support for this hypothesis is currently limited owing to few of studies examining the effects of either hCG or IFN-τ on circulating immune cell function. However, work carried out in eltoprazine later pregnancy

in cattle clearly supports similarities between humans and cattle in alterations in peripheral and endometrial immune cell populations.12 For example, in cattle there was an increase in peripheral cells exhibiting the T regulatory phenotype (CD4+ CD25+) as well as recruitment of these cells to the endometrium. T regulatory cells secrete IL-4 and can induce tolerance to paternal alloantigens and inhibition of T regulatory function is associated with compromised pregnancy.12 We recently conducted a transcriptional profiling experiment to identify genes regulated in PBL by pregnancy and progesterone in cattle82 (Ott and Gifford unpublished). Results from these studies clearly indicated that a large number of known interferon-stimulated genes increase in PBL of early pregnant cows. In addition, some genes not previously thought to be IFN responsive were also increased.