Regulatory T cells (Tregs) fulfill a central role in immune regulation. We reported previously that the integrin αEβ7 discriminates distinct subsets of murine CD4+ regulatory T cells. Use of this marker has now helped to unravel a fundamental dichotomy among regulatory T cells. αE −CD25+ cells expressed L-selectin and CCR7, enabling recirculation through lymphoid tissues. In contrast, αE-positive subsets (CD25+ and CD25−) displayed an effector/memory phenotype expressing high levels of E/P-selectin–binding ligands, multiple adhesion molecules as well as receptors for inflammatory chemokines, allowing efficient migration into inflamed sites. Accordingly, αE-expressing cells were found to be the most potent suppressors of inflammatory processes in disease models such as antigen-induced arthritis.

Regulatory T cells (Tregs) play a fundamental role in the suppression of different immune responses; however, compartments at which they exert suppressive functions in vivo are unknown. Although many groups have described the presence of Tregs within inflammatory sites, it has not been shown that inflamed tissues are, indeed, the sites of active suppression of ongoing immune reactions. Here, by using ␣ E ؉ effector/memory-like Tregs from fucosyltransferase VII-deficient animals, which lack E/P-selectin ligands and fail to migrate into inflamed sites, we analyzed the functional importance of appropriate Treg localization for in vivo suppressive capacity in an inflammation model. Lack of suppression by Tregs deficient in E/P-selectin ligands demonstrates that immigration into inflamed sites is a prerequisite for the resolution of inflammatory reactions in vivo because these selectin ligands merely regulate entry into inflamed tissues. In contrast, control of proliferation of naive CD4 ؉ T cells during the induction phase of the immune response is more efficiently exerted by the naive-like ␣ E ؊ CD25 ؉ Treg subset preferentially recirculating through lymph nodes when compared with its inflammation-seeking counterpart. [21][22][23] or inflamed intestine in induced colitis. 24 Moreover, a few studies demonstrated the capacity of Tregs to down-regulate established immune reactions, [24][25][26][27] suggesting that regulation might also act locally in the inflammatory environment.The resulting questions-in which compartment suppression by Tregs occurs and how critical is an appropriate localization of Tregs for their in vivo suppressive capacity-have not been addressed directly, as yet.We have previously shown that by use of the marker ␣ E (CD103) the Treg compartment can be subdivided into a lineage or differentiation stage of natural, naive-like ␣ E Ϫ CD25 ϩ Tregs and into that of ␣ E ϩ Tregs (either CD25 ϩ or CD25 Ϫ ) with the phenotype of effector/memory cells. 28,29 Whereas ␣ E Ϫ CD25 ϩ Tregs express high levels of CD62L and CCR7 and recirculate through lymph nodes, effector/memory-like ␣ E ϩ Tregs express high levels of inflammatory chemokine receptors and multiple adhesion molecules as well as selectin ligands and efficiently migrate into inflamed sites. Importantly, the integrin ␣ E ␤ 7 itself only seems to play a role for the retention within peripheral tissues, 30,31 but is not involved in the extravasation process of CD4 ϩ T lymphocytes. 32 In the present study it rather serves as a surrogate marker to identify inflammation-seeking Tregs.Migration of CD4 ϩ effector T cells into inflamed skin has been previously reported to be critically dependent on the expression of selectin ligands, 33,34 which bind to the partially redundantly acting E-and P-selectins, expressed almost exclusively on endothelium of For personal use only. on May 9, 2018. by guest www.bloodjournal.org From inflamed tissues. Biosynthesis of functional selectin ligands is mediated by several glycosyltransferases. 35 Among these enzymes, fuco...

The use of monoclonal antibodies (mAbs) as therapeutic tools has increased dramatically in the last decade and is now one of the mainstream strategies to treat cancer. Nonetheless, it is still not completely understood how mAbs mediate tumor cell elimination or the effector cells that are involved. Using intravital microscopy, we found that antibody-dependent phagocytosis (ADPh) by macrophages is a prominent mechanism for removal of tumor cells from the circulation in a murine tumor cell opsonization model. Tumor cells were rapidly recognized and arrested by liver macrophages (Kupffer cells). In the absence of mAbs, Kupffer cells sampled tumor cells; however, this sampling was not sufficient for elimination. By contrast, antitumor mAb treatment resulted in rapid phagocytosis of tumor cells by Kupffer cells that was dependent on the high-affinity IgG-binding Fc receptor (FcγRI) and the low-affinity IgG-binding Fc receptor (FcγRIV). Uptake and intracellular degradation were independent of reactive oxygen or nitrogen species production. Importantly, ADPh prevented the development of liver metastases. Tumor cell capture and therapeutic efficacy were lost after Kupffer cell depletion. Our data indicate that macrophages play a prominent role in mAb-mediated eradication of tumor cells. These findings may help to optimize mAb therapeutic strategies for patients with cancer by helping us to aim to enhance macrophage recruitment and activity.

Foxp3 + CD25 + CD4 + Treg play a fundamental role in the maintenance of self tolerance and the control of inflammatory reactions. Previous data demonstrated a division of labor between naive-and effector/memory-like Treg subsets, which is largely based on their lymph node-recirculating and inflammation-seeking migration behavior, respectively. The chemokine receptor CCR7 is expressed on both types of Treg subsets, albeit at different levels. Whether it fulfills similar or distinct roles in these subsets has not been studied so far. We here show that the recirculation of naive-like Treg through LN and, to some extent, the gut is dependent on CCR7. Lack of CCR7 not only prevents recirculation, but also almost completely abolishes the ability of naive-like Treg to control the priming phase of an immune response. In contrast, CCR7 deficiency in effector/memory-like Treg promotes their accumulation in inflamed sites, compatible with a role of CCR7 for exit from the tissue. Local Treg accumulation was accompanied by an enhanced suppression of inflammation. Together, our findings provide conclusive evidence that CCR7 expression on Treg differentially controls in vivo function of the naive-and effector/memory-like subsets.

Compelling evidence suggests that Foxp3 + CD25 + CD4 + Treg play a fundamental role in immunoregulation. We have previously demonstrated that Treg have to enter peripheral tissues to suppress ongoing inflammation. However, relatively little is known about how Treg acquire the expression of homing receptors required for tissue-or inflammationspecific migration. Migratory properties of conventional naïve T cells are shaped by the tissue microenvironment and organ-specific dendritic cells during priming. Here, we show that this basic concept also holds true for CD25 + CD4 + Treg: Priming of Treg within peripheral LN led to the expression of selectin ligands, which facilitate migration into inflamed skin, whereas activation within mesenteric LN led to induction of the integrin a 4 b 7 , which is required for migration into mucosal tissues. Furthermore, we could establish in vitro culture systems containing either dendritic cells from mesenteric and peripheral LN, or retinoic acid and IL-12 as polarizing compounds to induce mucosa-and skin-seeking Treg, respectively. Together, our results demonstrate that Treg, similarly to conventional T cells, can be configured with organ-selective homing properties allowing efficient targeting into distinct tissues. IntroductionMigration of T cell subsets to different tissues is determined by the combined expression of adhesion molecules and chemokine receptors (CCR) on the cell surfaces [1][2][3][4]. Among these homing receptors (HR), the integrin a 4 b 7 [5,6] and the chemokine receptor CCR9 [7][8][9] mediate the homing of T cell subsets to GALT such as mesenteric LN (mLN) and Peyer's patches (PP) and to the small intestinal lamina propria and the mucosal epithelium. In contrast, T cell trafficking to the skin is mediated by P-(P-lig) and E-(E-lig) selectin ligands [10,11] as well as .Recently, a number of studies have described that antigen-dependent differentiation of naïve T cells in lymphoid organs leads to the generation of effector T cells exhibiting a capacity to enter peripheral extralymphoid tissues [2]. Effector T cells generated in different lymphoid organs display distinct tissue tropism, which is regulated by an organ-specific induction of adhesion molecules and chemokine receptors during T cell priming [4,[15][16][17][18][19][20][21]. For example, T cells activated in mLN and PP draining the gut acquire high levels of the integrin a 4 b 7 , whereas activation in skin-draining peripheral LN (pLN) results in the upregulation of selectin ligands such as P-lig. Tissuespecific DC have been shown in a number of in vitro and in vivo studies to be involved in the instruction of naïve T cells [4,[17][18][19][20][22][23][24] reported that GALT DC were capable of converting metabolites of dietary vitamin A into retinoic acid (RA), which in turn induced T cell expression of a 4 b 7 and CCR9, leading to the generation of gut-tropic T cells. However, the factors, which are involved in the generation of skin-specific T cell homing in vivo, are largely unknown, although important ...

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SummaryNuclear receptor subfamily 2, group F, member 6 (NR2F6) is an orphan member of the nuclear receptor superfamily. Here, we show that genetic ablation of Nr2f6 significantly improves survival in the murine transgenic TRAMP prostate cancer model. Furthermore, Nr2f6−/− mice spontaneously reject implanted tumors and develop host-protective immunological memory against tumor rechallenge. This is paralleled by increased frequencies of both CD4+ and CD8+ T cells and higher expression levels of interleukin 2 and interferon γ at the tumor site. Mechanistically, CD4+ and CD8+ T cell-intrinsic NR2F6 acts as a direct repressor of the NFAT/AP-1 complex on both the interleukin 2 and the interferon γ cytokine promoters, attenuating their transcriptional thresholds. Adoptive transfer of Nr2f6-deficient T cells into tumor-bearing immunocompetent mice is sufficient to delay tumor outgrowth. Altogether, this defines NR2F6 as an intracellular immune checkpoint in effector T cells, governing the amplitude of anti-cancer immunity.

Forkhead box p3 (FOXP3) is known to program the acquisition of suppressive capacities in CD4؉ regulatory T cells (Treg), whereas its role in CD8 ؉ T cells is unknown. The current study investigates whether FOXP3 also acts as a Treg master switch in peripheral blood and tonsillar CD8 ؉ T cells. FOXP3 is a transcriptional regulator, repressing proinflammatory cytokine expression while inducing the expression of immune regulatory cytokines and Treg markers (8). By interacting with other transcription factors and chromatin modifying enzymes, FOXP3 induces epigenetic modifications that lead to the generation of Treg cells (9). Thus, FOXP3 acts as a master switch factor for Treg development similar to T-bet, GATA3, and retinoic acid receptor-related orphan receptor ␥t (ROR␥t; also known as RORC2) for the Th1, Th2, and Th17 cells, respectively. Initially, FOXP3 expression was detected only in CD25 high CD4 ϩ T cells in mice and humans (10 -13). However, its transgenic expression conferred suppressive activity to CD25 Ϫ CD4 ϩ T cells as well as to the CD8 ϩ subset of T cells (13,14). Whereas FOXP3 ϩ CD8 ϩ T cells constitute a minuscule fraction of circulating CD8 ϩ T cells in human blood, polyclonal activation in vitro induces expression of FOXP3 (15)(16)(17)(18)(19). Currently, it is not known how human FOXP3 ϩ CD8ϩ Treg cells develop in vivo and whether they possess suppressive activity.The development of anti-inflammatory CD4 ϩ Treg cells and the expression of their lineage-specific transcription factor FOXP3 has been shown to require . Surprisingly, the development of the proinflammatory Th17 cells and the expression of their suggested lineage-specific transcription factor ROR␥t depend also on TGF-␤ (21-23). In contrast to Treg cells, Th17 cell development requires the cytokine IL-6 in addition to TGF-␤, especially for the expression of the Th17 signature cytokine IL-17A (21). TGF-␤ is abundantly expressed in the MALT and plays a critical role in oral tolerance induction. As part of the MALT, palatine tonsils are located at the gateway of the respiratory and alimentary tracts where they are continually exposed to airborne and ingested Ags (24). Since the discrimination between harmless and harmful potential pathogens takes place in tonsils, they are a key site of effective immunity or tolerance. Whether CD8 ϩ Treg cells are present in tonsils and participate in the regulation of their immune response is currently unknown.In this study, we identify a FOXP3 ϩ CD8 ϩ T cell population in human tonsils that is predominantly CD25Ϫ and includes some IFN-␥-, TNF-␣-, and IL-17A-expressing cells. In vitro stimulation of naive CD8ϩ T cells induces FOXP3 ϩ CD8 ϩ T cells exhibiting The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.1 This work was supported in part by a Marie Curie Intra-European Fellowship from the European Commission (to K.S.) and Swiss Na...