Here, we report the identification of the ubiquitin-like gene UBD as a downstream element of FOXP3 in human activated regulatory CD4 þ CD25 hi T cells (T reg ). Retroviral transduction of UBD in human allo-reactive effector CD4 þ T helper (T h ) cells upregulates CD25 and mediates downregulation of IL4 and IL5 expression similar to overexpression of FOXP3. Moreover, UBD impairs T h cell proliferation without upregulation of FOXP3 and impairs calcium mobilization. In the presence of ionomycin, overexpression of UBD in T h cells leads to the induction of IL1R2 that resemble FOXP3-transduced T h cells and naturally derived T reg cells. A comparison of the transcriptome of FOXP3-and UBD-transduced T h cells with T reg cells allowed the identification of the gene LGALS3. However, high levels of LGALS3 protein expression were observed only in human CD4 þ CD25 hi derived T reg cells and FOXP3-transduced T h cells, whereas little was induced in UBD-transduced T h cells. Thus, UBD contributes to the anergic phenotype of human regulatory T cells and acts downstream in FOXP3 induced regulatory signaling pathways, including regulation of LGALS3 expression. High levels of LGALS3 expression represent a FOXP3-signature of human antigen-stimulated CD4 þ CD25 hi derived regulatory T cells.

Foxp3 functions as a lineage specification factor for the development of naturally occurring thymus-derived CD4+CD25+ regulatory T (Treg) cells. Recent evidence suggests that naive Foxp3−CD4+CD25− T cells can be converted in the periphery into Foxp3+ Treg cells. In this study, we have identified the G protein-coupled receptor (GPR)83 to be selectively up-regulated by CD4+CD25+ Treg cells of both murine and human origin in contrast to naive CD4+CD25− or recently activated T cells. Furthermore, GPR83 was induced upon overexpression of Foxp3 in naive CD4+CD25− T cells. Transduction of naive CD4+CD25− T cells with GPR83-encoding retroviruses did not confer in vitro suppressive activity. Nevertheless, GPR83-transduced T cells were able to inhibit the effector phase of a severe contact hypersensitivity reaction of the skin, indicating that GPR83 itself or GPR83-mediated signals conferred suppressive activity to conventional CD4+ T cells in vivo. Most strikingly, this in vivo acquisition of suppressive activity was associated with the induction of Foxp3 expression in GPR83-transduced CD4+ T cells under inflammatory conditions. Our results suggest that GPR83 might be critically involved in the peripheral generation of Foxp3+ Treg cells in vivo.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. T regulatory cell signatures

Comparison of the gene expression in human T regulatory cells and naïve cells using a T regulatory cell-specific microarray reveals cellspecific gene signatures.

Until today, second-line treatment of patients with metastatic RCC progressing under therapy with biological response modifiers remains an unresolved issue. The results of ongoing clinical trials evaluating novel targeted approaches can be expected with suspense.

Despite the known anti-proliferative and tumor-suppressive effects seen with retinoic acid (RA), treatment of metastatic renal cell carcinoma (RCC) failed to meet the initial expectations. As the exact mechanisms of action of RA and especially the role of the cellular RA binding proteins (CRABP) have not been elucidated yet, we investigated the expression of CRABP-I and its potential influence on RA response in RCC. Real-time RT-PCR analysis disclosed a significant lack of CRABP-I expression in four RCC cell lines and 12 primary RCC samples; in contrast, high expression levels were found in the respective adjacent normal kidney tissue. To further investigate the impact of CRABP-I on RA response in RCC, A-498 RCC cells were employed as a cellular model system. CRABP-I was stably transfected into A-498 cells which consequently displayed substantial resistance to all-trans (ATRA) and 9-cis RA compared to vector controls lacking CRABP-I. Comparison of gene expression profiles of ATRA-treated CRABP-I-expressing A-498 cells and vector controls revealed specific regulation of 54 of ∼20,000 genes tested on a selected human CodeLink^TM UniSet Bioarray, with a prominent modulation of genes involved in transcriptional control, signaling, apoptosis, cell cycle regulation and metabolism. The genetic changes reported here contribute to a better understanding of the role of RA in RCC. They also provide new insights into CRABP-I-mediated signaling and gene expression.