Cutting Edge: Decreased Accumulation and Regulatory Function of CD4+CD25high T Cells in Human STAT5b Deficiency

149

106

Objective: Interaction of ICOS with its ligand (ICOSL, B7-H2) promotes T cell responses. As CD4+CD25highFoxp3+ naturally occurring T regulatory cells in melanoma patients express ICOS, we investigated the impact of ICOS on naturally occurring T regulatory cell function. Methods: Expression of ICOS and T regulatory (Treg) cell markers was determined on CD4+CD25high T cells in PBMC and tumor-infiltrating lymphocytes from melanoma patients (n = 10) and PBMC of normal controls (n = 10) by multicolor flow cytometry. Suppression mediated by sorted ICOShigh and ICOSlow Treg was assessed in CFSE-based suppression assays with autologous CD4+CD25− responder cells (RC). Transwell inserts separating Treg from RC were used to evaluate suppression mechanisms used by Treg. ICOShigh or ICOSlow Treg were coincubated with RC ± TCR and IL-2 stimulation. ICOShigh and ICOS− Treg were also expanded under conditions previously shown to induce Tr1 from RC. Results: Treg in tumor-infiltrating lymphocytes expressed ICOS (mean fluorescence intensity = 70 ± 10), while Treg in PBMC had low ICOS expression (mean fluorescence intensity = 3.5 ± 2.5, p ≤ 0.001). ICOShigh Treg up-regulated Treg markers (p ≤ 0.0016) and mediated stronger suppression (p ≤ 0.001) relative to ICOSlow Treg. ICOShigh Treg induced Tr1 cells in nonactivated RC and Th2 cells in preactivated RC. ICOShigh Treg exposed to Tr1 cytokines expressed IL-10 and suppressed RC (92 ± 12%) in contrast to ICOSlow Treg, which mediated low suppression (21 ± 15%; p ≤ 0.0028). Conclusion: ICOShigh Treg can induce diverse immune responses in RC, depending on activation signals and cytokines present. ICOShigh Treg induce Tr1 or Th2 cells depending on the activation state of RC. In a “Tr1” cytokine milieu, ICOShigh Treg transit to Tr1.

Section: Til-derived Icos High Cd4 ϩ Cd25 High Treg Induce Differentimentioning

confidence: 97%

Expression of ICOS on Human Melanoma-Infiltrating CD4+CD25highFoxp3+ T Regulatory Cells: Implications and Impact on Tumor-Mediated Immune Suppression

Strauss

Bergmann

Szczepański

et al. 2008

149

106

“…Mice lacking isoforms 5A and 5B of STAT5, the IL-2 signaling factor, also develop multiorgan autoimmune disease and have reduced numbers of Treg cells (17)(18)(19). In humans STAT5b is also important for the in vivo accumulation of Treg cells (20) and it was recently shown that in vitro IL-2 up-regulates Foxp3 expression through a STAT5-dependent mechanism (21). However, most of the available data suggest that IL-2 signals are not essential for the generation of Treg cells, but rather to their peripheral survival and expansion (13,22,23).…”

Section: Discussionmentioning

confidence: 99%

Agonist-Driven Development of CD4+CD25+Foxp3+ Regulatory T Cells Requires a Second Signal Mediated by Stat6

Sanchez-Guajardo

Tanchot

O’Malley

et al. 2007

The factors that induce Foxp3 expression and regulatory T (Treg) cell development remain unknown. In this study, we investigated the role of STAT4 and STAT6 in agonist-driven generation of Ag-specific Foxp3-expressing Treg cells. Our findings indicate that fully efficient induction of Foxp3 expression and development of Ag-specific Treg cells requires the synergistic action of two signals: a TCR-mediated signal and a second signal mediated by STAT6. Indeed, by comparing the development of wild-type and STAT4- and STAT6-deficient hemagglutinin-specific T cells in the presence of hemagglutinin Ag, we found that the absence of STAT6 impaired the generation of Ag-specific CD4+CD25+Foxp3+ cells. Moreover, in transgenic mice expressing a constitutively active form of STAT6, we found that the fraction of CD4+Foxp3+ cells exceeds that of control wild-type littermates. Overall these findings support a role for the STAT6 pathway in Treg cell development and maintenance.

“…Also, studies of STAT5a and STAT5b double-knockout mice revealed the contribution of STAT5 molecules to nTreg development because a subset of these mice exhibited autoimmune pathology very similar to IL-2 or IL-2R knockout mice (7). A human patient with a STAT5b mutation displayed immune dysregulation associated with decreased numbers and impaired suppressive ability of CD4 ϩ CD25 high cells, indicating both developmental and functional defects of nTreg cells (8). An essential role of STAT5 molecules in the IL-2/IL-2R signaling pathway was confirmed by experiments using mice with an IL-2R␤ mutation, which exclusively activates STAT5 (4).…”

mentioning

confidence: 99%

The Production of IL-10 by Human Regulatory T Cells Is Enhanced by IL-2 through a STAT5-Responsive Intronic Enhancer in the IL-10 Locus

Tsuji-Takayama

Suzuki

Yamamoto

et al. 2008

STAT5 molecules are key components of the IL-2 signaling pathway, the deficiency of which often results in autoimmune pathology due to a reduced number of CD4+CD25+ naturally occurring regulatory T (Treg) cells. One of the consequences of the IL-2-STAT5 signaling axis is up-regulation of FOXP3, a master control gene for naturally occurring Treg cells. However, the roles of STAT5 in other Treg subsets have not yet been elucidated. We recently demonstrated that IL-2 enhanced IL-10 production through STAT5 activation. This occurred in two types of human Treg cells: a novel type of umbilical cord blood-derived Treg cell, termed HOZOT, and Tr1-like Treg cells, IL-10-Treg. In this study, we examined the regulatory mechanisms of IL-10 production in these Treg cells, focusing specifically on the roles of STAT5. By performing bioinformatic analysis on the IL-10 locus, we identified one STAT-responsive element within intron 4, designated I-SRE-4, as an interspecies-conserved sequence. We found that I-SRE-4 acted as an enhancer element, and clustered CpGs around the I-SRE-4 were hypomethylated in IL-10-producing Treg cells, but not in other T cells. A gel-shift analysis using a nuclear extract from IL-2-stimulated HOZOT confirmed that CpG DNA methylation around I-SRE-4 reduced STAT5 binding to the element. Chromatin immunoprecipitation analysis revealed the in situ binding of IL-2-activated STAT5 to I-SRE-4. Thus, we provide molecular evidence for the involvement of an IL-2-STAT5 signaling axis in the expression of IL-10 by human Treg cells, an axis that is regulated by the intronic enhancer, I-SRE-4, and epigenetic modification of this element.