It is likely that the failure to observe disease during this time period was secondary to the persistence of some Treg cells that maintained Foxp3 expression. A similar absence of disease induction was seen in another study in which Foxp3+ T cells were transferred to RAG−/− recipients [31]. While 50% of the cells lost expression of Foxp3, the recipients did not develop BMN 673 manufacturer IBD. However, when the Foxp3− cells were isolated and transferred to secondary RAG−/− mice, the recipients did develop tissue inflammation. Taken together, GITR activation on Treg cells can

have different outcomes depending on the experimental context ranging from expansion in normal mice to death in the IBD model. This dual action of GITR engagement on Treg cells is not unexpected, as similar to other members of the TNFRSF, GITR might activate more than selleckchem one signaling pathway. Activation of the NF-κB pathway may result in Treg-cell expansion [32], while GITR

signaling via Siva may result in apoptosis [33]. It also remains possible that the rapid induction of Treg-cell proliferation in a highly proinflammatory environment may result in activation-induced cell death via FAS/FAS-L or TNF/TNFR. Taken together, the translation of studies of GITR function in the mouse model to the use of Fc-GITR-L or agonist mAbs in man should be undertaken with caution depending on the disease (autoimmunity versus tumor immunity) under study and

the immune status of the host. C57BL/6 mice were obtained from cAMP the National Cancer Institute (Frederick, MD). Foxp3-GFP mice were obtained from Dr. V.J. Kuchroo (Harvard University, Boston, MA) and maintained by Taconic Farms (Germantown, NY) under contract by NIAID. RAG−/− mice obtained from Taconic Farms. GITR+/− embryos (Sv129 × B6) were provided by C. Ricarrdi (Perugia University Medical School, Perugia, Italy). Rederived GITR+/− mice were backcrossed once with C57BL/6 mice, and the resulting progeny were screened for the mutant allele by PCR. The identified GITR+/− progeny were then intercrossed to generate GITR−/− mice. All mice were bred and housed at National Institutes of Health/National Institute of Allergy and Infectious Diseases facilities under specific pathogen-free conditions. All studies were approved by the Animal Care and Use Committee of the NIAID. Fc-GITR-L, construct #178–14, was prepared as previously described [15]. Anti-CD4 V-500 and PE-Cy5, anti-CD25 PE, anti-GITR-PE, anti-CD44 Alexa Fluor 700, CD45.2 allophycocyanin-eFluor 780, anti-CD45.1 PE-Cy7, fixable viability dye allophycocyanin-eFluor 780 and eFluor 450, anti-Foxp3 PE, eFlour 450 and allophycocyanin, ant-IL-17 Alexa Fluor 647 and anti-IFN-γ PE-Cy7 were purchased from (eBioscience, San Diego, CA).