Manuela Battaglia

Interleukin-10-secreting type 1 regulatory T cells in rodents and humans

Summary:  Interleukin‐10 (IL‐10)‐secreting T regulatory type 1 (Tr1) cells are defined by their specific cytokine production profile, which includes the secretion of high levels of IL‐10 and transforming growth factor‐β(TGF‐β), and by their ability to suppress antigen‐specific effector T‐cell responses via a cytokine‐dependent mechanism. In contrast to the naturally occurring CD4+CD25+ T regulatory cells (Tregs) that emerge directly from the thymus, Tr1 cells are induced by antigen stimulation via an IL‐10‐dependent process in vitro and in vivo. Specialized IL‐10‐producing dendritic cells, such as those in an immature state or those modulated by tolerogenic stimuli, play a key role in this process. We propose to use the term Tr1 cells for all IL‐10‐producing T‐cell populations that are induced by IL‐10 and have regulatory activity. The full biological characterization of Tr1 cells has been hampered by the difficulty in generating these cells in vitro and by the lack of specific marker molecules. However, it is clear that Tr1 cells play a key role in regulating adaptive immune responses both in mice and in humans. Further work to delineate the specific molecular signature of Tr1 cells, to determine their relationship with CD4+CD25+ Tregs, and to elucidate their respective role in maintaining peripheral tolerance is crucial to advance our knowledge on this Treg subset. Furthermore, results from clinical protocols using Tr1 cells to modulate immune responses in vivo in autoimmunity, transplantation, and chronic inflammatory diseases will undoubtedly prove the biological relevance of these cells in immunotolerance.

Rapamycin Promotes Expansion of Functional CD4+CD25+FOXP3+ Regulatory T Cells of Both Healthy Subjects and Type 1 Diabetic Patients

CD4+CD25+FOXP3+ T regulatory cells (Tregs) are pivotal for the induction and maintenance of peripheral tolerance in both mice and humans. Rapamycin has been shown to promote tolerance in experimental models and to favor CD4+CD25+ Treg-dependent suppression. We recently reported that rapamycin allows in vitro expansion of murine CD4+CD25+FoxP3+ Tregs, which preserve their suppressive function. In the current study, we show that activation of human CD4+ T cells from healthy subjects in the presence of rapamycin leads to growth of CD4+CD25+FOXP3+ Tregs and to selective depletion of CD4+CD25− T effector cells, which are highly sensitive to the antiproliferative effect of the compound. The rapamycin-expanded Tregs suppress proliferation of both syngeneic and allogeneic CD4+ and CD8+ T cells. Interestingly, rapamycin promotes expansion of functional CD4+CD25+FOXP3+ Tregs also in type 1 diabetic patients, in whom a defect in freshly isolated CD4+CD25+ Tregs has been reported. The capacity of rapamycin to allow growth of functional CD4+CD25+FOXP3+ Tregs, but also to deplete T effector cells, can be exploited for the design of novel and safe in vitro protocols for cellular immunotherapy in T cell-mediated diseases.

Regulatory T-cell immunotherapy for tolerance to self antigens and alloantigens in humans

Substantial progress in understanding the biology of regulatory T cells and their roles in health and disease has been achieved in the past 10 years. This has led to an increasing interest in the possibility of using regulatory T cells as a biological therapy to preserve and restore tolerance to self antigens and alloantigens. Immunotherapy by the adoptive transfer of regulatory T cells may have several advantages over conventional treatments. However, several hurdles have to be overcome before such a therapy can enter clinical practice. This Review summarizes our current knowledge of regulatory T cells, illustrates the ongoing regulatory T-cell-based clinical trials, analyses the strengths and pitfalls of this new therapeutic approach, and highlights the future perspectives.

Human CD25+CD4+ T Suppressor Cell Clones Produce Transforming Growth Factor β, but not Interleukin 10, and Are Distinct from Type 1 T Regulatory Cells

T regulatory (Tr) cells are essential for the induction of peripheral tolerance. Several types of Tr cells exist, including CD4+ T cells which express CD25 constitutively and suppress immune responses via direct cell-to-cell interactions, and type 1 T regulatory (Tr1) cells, which function via secretion of interleukin (IL)-10 and transforming growth factor (TGF)-β. The relationship between CD25+CD4+ T cells and Tr1 cells remains unclear. Here, we demonstrate at the clonal level that Tr1 and CD25+CD4+ T cells are two distinct subsets of regulatory cells with different cytokine production profiles. Furthermore, CD25−CD4+ T cells can be rendered anergic by IL-10 and differentiated into Tr1 cells in the absence of CD25+CD4+ T cells. Cloned human CD25+CD4+ T cell populations are heterogeneous and only a subset of clones continues to express high levels of CD25 and is suppressive. The intensity of CD25, cytotoxic T lymphocyte antigen (CTLA)-4, and glucocorticoid-induced tumor necrosis factor (TNF) receptor expression correlates with the suppressive capacity of the T cell clones. None of the CD25+CD4+ T cell clones with suppressive function produce IL-10, but all produce TGF-β. Suppression mediated by CD25+CD4+ T cell clones is partially dependent on TGF-β, but not on constitutive high expression of CD25. Together these data indicate that naturally occurring human CD25+CD4+ T cells are distinct from IL-10–producing Tr1 cells.

Th17 Cells Express Interleukin-10 Receptor and Are Controlled by Foxp3− and Foxp3+ Regulatory CD4+ T Cells in an Interleukin-10-Dependent Manner

T helper 17 (Th17) cells are important for host defense against extracellular microorganisms. However, they are also implicated in autoimmune and chronic inflammatory diseases, and as such need to be tightly regulated. The mechanisms that directly control committed pathogenic Th17 cells in vivo remain unclear. We showed here that IL-17A-producing CD4+ T cells expressed interleukin-10 receptor α (IL-10Rα) in vivo. Importantly, T cell-specific blockade of IL-10 signaling led to a selective increase of IL-17A+IFN-γ⁻ (Th17) and IL-17A+IFN-γ+ (Th17+Th1) CD4+ T cells during intestinal inflammation in the small intestine. CD4+Foxp3⁻ IL-10-producing (Tr1) cells and CD4+Foxp3+ regulatory (Treg) cells were able to control Th17 and Th17+Th1 cells in an IL-10-dependent manner in vivo. Lastly, IL-10 treatment of mice with established colitis decreased Th17 and Th17+Th1 cell frequencies via direct signaling in T cells. Thus, IL-10 signaling directly suppresses Th17 and Th17+Th1 cells.

Differentiation of type 1 T regulatory cells (Tr1) by tolerogenic DC-10 requires the IL-10-dependent ILT4/HLA-G pathway

Type 1 T regulatory (Tr1) cells suppress immune responses in vivo and in vitro and play a key role in maintaining tolerance to self- and non-self-antigens. Interleukin-10 (IL-10) is the crucial driving factor for Tr1 cell differentiation, but the molecular mechanisms underlying this induction remain unknown. We identified and characterized a subset of IL-10-producing human dendritic cells (DCs), termed DC-10, which are present in vivo and can be induced in vitro in the presence of IL-10. DC-10 are CD14(+), CD16(+), CD11c(+), CD11b(+), HLA-DR(+), CD83(+), CD1a(-), CD1c(-), express the Ig-like transcripts (ILTs) ILT2, ILT3, ILT4, and HLA-G antigen, display high levels of CD40 and CD86, and up-regulate CD80 after differentiation in vitro. DC-10 isolated from peripheral blood or generated in vitro are potent inducers of antigen-specific IL-10-producing Tr1 cells. Induction of Tr1 cells by DC-10 is IL-10-dependent and requires the ILT4/HLA-G signaling pathway. Our data indicate that DC-10 represents a novel subset of tolerogenic DCs, which secrete high levels of IL-10, express ILT4 and HLA-G, and have the specific function to induce Tr1 cells.

WASP regulates suppressor activity of human and murine CD4(+)CD25(+)FOXP3(+) natural regulatory T cells.

A large proportion of Wiskott-Aldrich syndrome (WAS) patients develop autoimmunity and allergy. CD4+CD25+FOXP3+ natural regulatory T (nTreg) cells play a key role in peripheral tolerance to prevent immune responses to self-antigens and allergens. Therefore, we investigated the effect of WAS protein (WASP) deficiency on the distribution and suppressor function of nTreg cells. In WAS−/− mice, the steady-state distribution and phenotype of nTreg cells in the thymus and spleen were normal. However, WAS−/− nTreg cells engrafted poorly in immunized mice, indicating perturbed homeostasis. Moreover, WAS−/− nTreg cells failed to proliferate and to produce transforming growth factor β upon T cell receptor (TCR)/CD28 triggering. WASP-dependent F-actin polarization to the site of TCR triggering might not be involved in WAS−/− nTreg cell defects because this process was also inefficient in wild-type (WT) nTreg cells. Compared with WT nTreg cells, WAS−/− nTreg cells showed reduced in vitro suppressor activity on both WT and WAS−/− effector T cells. Similarly, peripheral nTreg cells were present at normal levels in WAS patients but failed to suppress proliferation of autologous and allogeneic CD4+ effector T cells in vitro. Thus, WASP appears to play an important role in the activation and suppressor function of nTreg cells, and a dysfunction or incorrect localization of nTreg cells may contribute to the development of autoimmunity in WAS patients.

Expansion of Th17 cells and functional defects in T regulatory cells are key features of the pancreatic lymph nodes in patients with type 1 diabetes.

OBJECTIVE Autoimmune diseases, including type 1 diabetes, are thought to have a Th17-cell bias and/or a T-regulatory cell (Treg) defect. Understanding whether this is a hallmark of patients with type 1 diabetes is a crucial question that is still unsolved, largely due to the difficulties of accessing tissues targeted by the disease. RESEARCH DESIGN AND METHODS We phenotypically and functionally characterized Th17 cells and Tregs residing in the pancreatic-draining lymph nodes (PLNs) of 19 patients with type 1 diabetes and 63 nondiabetic donors and those circulating in the peripheral blood of 14 type 1 diabetic patients and 11 healthy subjects. RESULTS We found upregulation of Th17 immunity and functional defects in CD4+CD25bright Tregs in the PLNs of type 1 diabetic subjects but not in their peripheral blood. In addition, the proinsulin-specific Treg-mediated control was altered in the PLNs of diabetic patients. The dysfunctional Tregs isolated from diabetic subjects did not contain contaminant effector T cells and were all epigenetically imprinted to be suppressive, as defined by analysis of the Treg-specific demethylated region within the forkhead box P3 (FOXP3) locus. CONCLUSIONS These data provide evidence for an unbalanced immune status in the PLNs of type 1 diabetic subjects, and treatments restoring the immune homeostasis in the target organ of these patients represent a potential therapeutic strategy.

Induction of Tolerance in Type 1 Diabetes via Both CD4+CD25+ T Regulatory Cells and T Regulatory Type 1 Cells

Success in developing novel therapies to recommence self-tolerance in autoimmunity depends on the induction of T regulatory (Tr) cells. Here, we report that rapamycin combined with interleukin (IL)-10 efficiently blocks type 1 diabetes development and induces long-term immunotolerance in the absence of chronic immunosuppression in nonobese diabetic (NOD) mice. Rapamycin mediates accumulation in the pancreas of suppressive CD4+CD25+FoxP3+ Tr cells, which prevent diabetes. IL-10 induces Tr type 1 (Tr1) cells, which reside in the spleen and prevent migration of diabetogenic T-cells to the draining lymph nodes. These two Tr cell subsets act in concert to control diabetogenic T-cells that are still present in long-term tolerant mice. Rapamycin plus IL-10 treatment, promoting distinct subsets of Tr cells, may constitute a novel and potent tolerance-inducing protocol for immune-mediated diseases.

STAT5-signaling cytokines regulate the expression of FOXP3 in CD4+CD25+ regulatory T cells and CD4+CD25-effector T cells

Forkhead box P3 (FOXP3) is considered a specific marker for CD4(+)CD25(+) regulatory T (Treg) cells, but increasing evidence suggests that human CD4(+)CD25(-) effector T (Teff) cells can transiently express FOXP3 upon activation. We demonstrate that the signal transducer and activator of transcription 5 (STAT5)-signaling cytokines, IL-2, IL-15 and to a lesser extent IL-7, induce FOXP3 up-regulation in vitro in activated human Teff cells. In contrast, cytokines which do not activate STAT5, such as IL-4 or transforming growth factor-beta alone, do not directly induce FOXP3 expression in activated Teff cells. Moreover, expression of a constitutively active form of STAT5a is sufficient to induce FOXP3 expression in Teff cells. Expression of FOXP3 in activated Teff cells requires both TCR-mediated activation and endogenous IL-2, but is not dependent on cell division and does not induce suppressive function. The presence of STAT5-activating cytokines is also required to maintain high FOXP3 expression and suppressive activity of Treg cells in vitro. These data indicate that activation of STAT5 sustains FOXP3 expression in both Treg and Teff cells and contribute to our understanding of how cytokines affect the expression of FOXP3.