IL-12R beta 2 promotes the development of CD4+CD25+ regulatory T cells

Single-cell RNA sequencing illuminates the ontogeny, conservation and diversification of cartilaginous and bony fish lymphocytes

Elucidating cellular architecture and cell-type evolution across species is central to understanding immune system function and susceptibility to disease. Adaptive immunity is a shared trait of the common ancestor of cartilaginous and bony fishes. However, evolutionary features of lymphocytes in these two jawed vertebrates remain unclear. Here, we present a single-cell RNA sequencing atlas of immune cells from cartilaginous (white-spotted bamboo shark) and bony (zebrafish and Chinese tongue sole) fishes. Cross-species comparisons show that the same cell types across different species exhibit similar transcriptional profiles. In the bamboo shark, we identify a phagocytic B cell population expressing several pattern recognition receptors, as well as a T cell sub-cluster co-expressing both T and B cell markers. In contrast to a division by function in the bony fishes, we show close linkage and poor functional specialization among lymphocytes in the cartilaginous fish. Our cross-species single-cell comparison presents a resource for uncovering the origin and evolution of the gnathostome immune system.

A Bioinformatics Investigation of Hub Genes Involved in Treg Migration and Its Synergistic Effects, Using Immune Checkpoint Inhibitors for Immunotherapies

This study aimed to identify hub genes involved in regulatory T cell (Treg) function and migration, offering insights into potential therapeutic targets for cancer immunotherapy. We performed a comprehensive bioinformatics analysis using three gene expression microarray datasets from the GEO database. Differentially expressed genes (DEGs) were identified to pathway enrichment analysis to explore their functional roles and potential pathways. A protein-protein interaction network was constructed to identify hub genes critical for Treg activity. We further evaluated the co-expression of these hub genes with immune checkpoint proteins (PD-1, PD-L1, CTLA4) and assessed their prognostic significance. Through this comprehensive analysis, we identified CCR8 as a key player in Treg migration and explored its potential synergistic effects with ICIs. Our findings suggest that CCR8-targeted therapies could enhance cancer immunotherapy outcomes, with breast invasive carcinoma (BRCA) emerging as a promising indication for combination therapy. This study highlights the potential of CCR8 as a biomarker and therapeutic target, contributing to the development of targeted cancer treatment strategies.

The Mechanisms of Effector Th Cell Responses Contribute to Treg Cell Function: New Insights into Pathogenesis and Therapy of Asthma

CD4 ⁺ helper T (Th) cell subsets are critically involved in the pathogenesis of asthma. Naive Th cells differentiate into different subsets under the stimulation of different sets of cytokines, and the differentiation process is dominantly driven by lineage specific transcription factors, such as T-bet (Th1), GATA3 (Th2), RORγt (Th17) and Foxp3 (Treg). The differentiation mechanisms driven by these transcription factors are mutually exclusive, resulting in functional inhibition of these Th subsets to each other, particularly prominent between effector Th cells and Treg cells, such as Th2 versus Treg cells and Th17 versus Treg cells. Being of significance in maintaining immune homeostasis, the balance between effector Th cell response and Treg cell immunosuppression provides an immunological theoretical basis for us to understand the immunopathological mechanism and develop the therapy strategies of asthma. However, recent studies have found that certain factors involved in effector Th cells response, such as cytokines and master transcription factors (IL-12 and T-bet of Th1, IL-4 and GATA3 of Th2, IL-6 and RORγt of Th17), not only contribute to immune response of effector Th cells, but also promote the development and function of Treg cells, therefore bridging the interplay between effector Th cell immune responses and Treg cell immunosuppression. Although we have an abundant knowledge concerning the role of these cytokines and transcription factors in effector Th cell responses, our understanding on their role in Treg cell development and function is scattered thus need to be summarized. This review summarized the role of these cytokines and transcription factors involved in effector Th cell responses in the development and function of Treg cells, in the hope of providing new insights of understanding the immunopathological mechanism and seeking potential therapy strategies of asthma.

Thymus-Derived CD4+CD8+ Cells Reside in Mediastinal Adipose Tissue and the Aortic Arch

Double-positive CD4+CD8αβ+ (DP) cells are thought to reside as T cell progenitors exclusively within the thymus. We recently discovered an unexpected CD4+ and CD8αβ+ immune cell population in healthy and atherosclerotic mice by single-cell RNA sequencing. Transcriptomically, these cells resembled thymic DPs. Flow cytometry and three-dimensional whole-mount imaging confirmed DPs in thymus, mediastinal adipose tissue, and aortic adventitia, but nowhere else. Deep transcriptional profiling revealed differences between DP cells isolated from the three locations. All DPs were dependent on RAG2 expression and the presence of the thymus. Mediastinal adipose tissue DPs resided in close vicinity to invariant NKT cells, which they could activate in vitro. Thymus transplantation failed to reconstitute extrathymic DPs, and frequencies of extrathymic DPs were unaltered by pharmacologic inhibition of S1P1, suggesting that their migration may be locally confined. Our results define two new, transcriptionally distinct subsets of extrathymic DPs that may play a role in aortic vascular homeostasis.

Interleukin-12 receptor β2 from grass carp: Molecular characterization and its involvement in Aeromonas hydrophila-induced intestinal inflammation

Interleukin-12 receptor β2 (IL-12Rβ2) is a signaling subunit of heterodimeric receptors for IL-12 and IL-35. It plays important regulatory functions in the development of Th1 cells and in the expression of inflammatory cytokines in mammals and other higher vertebrates. However, little is known about IL-12Rβ2 in teleost fish. In this work, we have cloned and characterized IL-12Rβ2 from grass carp (Ctenopharyngodon idella). The full-length cDNA of grass carp IL-12Rβ2 is 2875 bp, which encodes a mature protein with 741 amino acids. This mature protein contains three fibronectin type III domains, a transmembrane helix, and CXW and WSXWS-like motifs that are characteristic of the type I cytokine receptor family. Phylogenetic analysis revealed that cyprinid fish IL-12Rβ2 formed a single branch, clearly separated from those of other vertebrates. We expressed and purified a recombinant grass carp IL-12Rβ2 protein containing major antigenic regions, which was used to raise a polyclonal antibody. The specificity of the antibody was assessed by Western blotting analysis of whole cell lysates from Escherichia coli cells expressing the recombinant IL-12Rβ2, grass carp intestinal intraepithelial lymphocytes, and cultured C. idella kidney cells. To explore the potential regulatory role of IL-12Rβ2 in inflammation, we generated an intestinal inflammation model by anal intubation of fish with Aeromonas hydrophila. Immunohistochemical staining of the inflamed intestines revealed that IL-12Rβ2 expression is consistent with inflammatory cell recruitment during intestinal inflammation. Real-time quantitative PCR revealed that IL-12Rβ2 is widely expressed in normal tissues and is up-regulated in most tissues after infecting with A. hydrophila. We found that IL-12Rβ2, IL-12p35, and interferon-γ were expressed in similar patterns in the intestines during inflammation. Taken together, our results suggest that IL-12Rβ2 is involved in the regulation of intestinal inflammation.

Molecular and functional heterogeneity of IL-10-producing CD4+ T cells

IL-10 is a prototypical anti-inflammatory cytokine, which is fundamental to the maintenance of immune homeostasis, especially in the intestine. There is an assumption that cells producing IL-10 have an immunoregulatory function. However, here we report that IL-10-producing CD4⁺ T cells are phenotypically and functionally heterogeneous. By combining single cell transcriptome and functional analyses, we identified a subpopulation of IL-10-producing Foxp3^neg CD4⁺ T cells that displays regulatory activity unlike other IL-10-producing CD4⁺ T cells, which are unexpectedly pro-inflammatory. The combinatorial expression of co-inhibitory receptors is sufficient to discriminate IL-10-producing CD4⁺ T cells with regulatory function from others and to identify them across different tissues and disease models in mice and humans. These regulatory IL-10-producing Foxp3^neg CD4⁺ T cells have a unique transcriptional program, which goes beyond the regulation of IL-10 expression. Finally, we found that patients with Inflammatory Bowel Disease demonstrate a deficiency in this specific regulatory T-cell subpopulation.

Tr1 cells are considered an immunosuppressive CD4 T cell population producing IL-10. Here the authors show that IL-10 is insufficient for Tr1 immunosuppression, define surface markers and transcriptional program of the immunosuppressive subset within Tr1, and reveal its deficiency in patients with IBD.

Modulatory Influence of Segmented Filamentous Bacteria on Transcriptomic Response of Gnotobiotic Mice Exposed to TCDD

Environmental toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR), are known to induce host toxicity and structural shifts in the gut microbiota. Key bacterial populations with similar or opposing functional responses to AhR ligand exposure may potentially help regulate expression of genes associated with immune dysfunction. To examine this question and the mechanisms for AhR ligand-induced bacterial shifts, C57BL/6 gnotobiotic mice were colonized with and without segmented filamentous bacteria (SFB) – an immune activator. Mice were also colonized with polysaccharide A producing Bacteroides fragilis – an immune suppressor to serve as a commensal background. Following colonization, mice were administered TCDD (30 μg/kg) every 4 days for 28 days by oral gavage. Quantified with the nCounter^® mouse immunology panel, opposing responses in ileal gene expression (e.g., genes associated with T-cell differentiation via the class II major histocompatibility complex) as a result of TCDD dosing and SFB colonization were observed. Genes that responded to TCDD in the presence of SFB did not show a significant response in the absence of SFB, and vice versa. Regulatory T-cells examined in the mesenteric lymph-nodes, spleen, and blood were also less impacted by TCDD in mice colonized with SFB. TCDD-induced shifts in abundance of SFB and B. fragilis compared with previous studies in mice with a traditional gut microbiome. With regard to the mouse model colonized with individual populations, results indicate that TCDD-induced host response was significantly modulated by the presence of SFB in the gut microbiome, providing insight into therapeutic potential between AhR ligands and key commensals.

Immunological, anti-angiogenic and clinical effects of intratumoral interleukin 12 electrogene therapy combined with metronomic cyclophosphamide in dogs with spontaneous cancer: A pilot study

The immunological, anti-angiogenic and clinical effects of metronomic cyclophosphamide and 3 consecutive intratumoral interleukin (IL)-12 gene therapy (electrogene therapy (EGT)) treatments were evaluated in 6 dogs with spontaneous cancer. In all dogs, a decrease in peripheral leukocytes 2 days after IL-12 EGT coincided with erythema and swelling of the tumor. In the tumor, a transient increase in IL-12 levels was measured, whereas a continuous increase in interferon γ (IFNγ) and thrombospondin 1 (TSP-1) were determined in contrast to a continuous decrease in vascular endothelial growth factor (VEGF). In the serum, a transient increase in IL-12 and IL-10 levels were noted in contrast to a transient decrease in VEGF and TSP-1. The treatment resulted in a significant anti-angiogenic effect. Although all primary tumors continued to progress in time, this progression was slower than before treatment according to the contrast-enhanced ultrasound data. Besides the encouraging immunostimulatory and anti-angiogenic effects observed in all dogs we also noticed in 4 out of 6 dogs clinically relevant improvements in quality of life and weight. These results hold great promise for combinatorial strategies of IL-12 EGT and metronomic chemotherapy with conventional antitumor (immuno)therapies.

Functional analysis of differences in transcriptional activity conferred by genetic variants in the 5' flanking region of the IL12RB2 gene

Interleukin 12 receptor β chain (IL12RB2) is a crucial regulatory factor involved in cell-mediated immune responses, and genetic variants of the gene encoding IL12RB2 are associated with susceptibility to various immune-related diseases. We previously demonstrated that haplotypes with single nucleotide polymorphisms (SNPs) in the 5' flanking region of IL12RB2, including -1035A>G (rs3762315) and -1023A>G (rs3762316), affect the expression of IL12RB2, thereby altering susceptibility to leprosy and periodontal diseases. In the present study, we identified transcription factors associated with the haplotype-specific transcriptional activity of IL12RB2 in T cells and NK cells. The -1023G polymorphism was found to create a consensus binding site for the transcription factor activating protein (AP)-1, and enzyme-linked immunosorbent assay (ELISA)-based binding assays showed that these SNPs enhanced AP-1 binding to this region. In reporter assays, suppression of JunB expression using siRNA eliminated differences in the -1035G/-1023G and -1035A/-1023A regions containing IL12RB2 promoter activity in Jurkat T cells and NK3.3 cells. These results suggested that the -1035/-1023 polymorphisms created differential binding affinities for JunB that could lead to differential IL12RB2 expression. Moreover, the -1035G and -1035A alleles formed binding sites for GATA-3 and myocyte enhancer factor-2 (MEF-2), respectively. Our data indicated that in addition to JunB, the SNP at -1035/-1023 influenced GATA-3 and MEF-2 binding affinity, potentially altering IL12RB2 transcriptional activity. These findings confirm the effects of rs3762315 and rs3762316 on IL12RB2 transcription. These genetic variants may alter cellular activation of T cells and NK cells and modify cell-mediated immune responses.

Systemic IL-12 burst expands intestinal T-lymphocyte subsets bearing the α₄ β₇ integrin in mice

The intestinal immune system is complex and displays unique anatomic and functional characteristics. Numerous immune cell subsets are located beneath the epithelial barrier and their activity is highly regulated. Using hydrodynamic shear of IL-12 cDNA to achieve systemic expression of IL-12 in mice, we evaluated the effect of a transient burst of this cytokine on the activation status of T cells from Peyer's patches (PPs), mesenteric lymph nodes (MLNs), and colonic lamina propria (LP). Following systemic IL-12 release, intestinal T lymphocytes became activated, exhibiting a CD44(high) CD62L(-) phenotype. After 5 days of the cytokine burst, the frequency of α4β7(+) CD4(+) and CD8(+) cells increased, and CD8(+) α4β7(+) cells mainly expressed T bet, a critical regulator of the Th1 differentiation program. The incremental increase in α4β7 expression involved the IL-12 receptor-signal transducer and activator of transcription (STAT)-4 axis, and occurred independently of IFN-γ, IL-4, IL-10, and TNF-α signaling. Moreover, IL-12 priming exacerbated the outcome of acute dextran sodium sulphate (DSS)-induced colitis with higher scores of weight loss, blood in stool, and diarrhea and lower hematocrit. Together, our findings demonstrate that systemic polarizing signals could effectively expand the number of effector cells able to home to the LP and contribute to local inflammation.

Unstable Foxp3+ regulatory T cells and altered dendritic cells are associated with lipopolysaccharide-induced fetal loss in pregnant interleukin 10-deficient mice

Maternal interleukin (IL) 10 deficiency elevates susceptibility to fetal loss induced by the model Toll-like receptor agonist lipopolysaccharide, but the mechanisms are not well elucidated. Here, we show that Il10 null mutant (Il10(-/-)) mice exhibit altered local T cell responses in pregnancy, exhibiting pronounced hyperplasia in para-aortic lymph nodes draining the uterus with >6-fold increased CD4(+) and CD8(+) T cells compared with wild-type controls. Among these CD4(+) cells, Foxp3(+) T regulatory (Treg) cells were substantially enriched, with 11-fold higher numbers at Day 9.5 postcoitum. Lymph node hypertrophy in Il10(-/-) mice was associated with more activated phenotypes in dendritic cells and macrophages, with elevated expression of MHCII, scavenger receptor, and CD80. Affymetrix microarray revealed an altered transcriptional profile in Treg cells from pregnant Il10(-/-) mice, with elevated expression of Ctse (cathepsin E), Il1r1, Il12rb2, and Ifng. In vitro, Il10(-/-) Treg cells showed reduced steady-state Foxp3 expression, and polyclonal stimulation caused greater loss of Foxp3 and reduced capacity to suppress IL17 in CD4(+)Foxp3(-) T cells. We conclude that despite a substantially expanded Treg cell pool, the diminished stability of Treg cells, increased numbers of effector T cells, and altered phenotypes in dendritic cells and macrophages in pregnancy all potentially confer vulnerability to inflammation-induced fetal loss in Il10(-/-) mice. These findings suggest that IL10 has a pivotal role in facilitating robust immune protection of the fetus from inflammatory challenge and that IL10 deficiency could contribute to human gestational disorders in which altered T cell responses are implicated.

Elevated levels of serum IL-12 and IL-18 are associated with lower frequencies of CD4(+)CD25 (high)FOXP3 (+) regulatory t cells in young patients with type 1 diabetes

Type 1 diabetes is thought to involve chronic inflammation, which is manifested by the activation and expression of different inflammatory mediators. IL-12 and IL-18 are two cytokines that have been shown to exert strong proinflammatory activity and have been implicated in the pathogenesis of type 1 diabetes in mice and humans. The overproduction of proinflammatory mediators is controlled by specialized T cell subset, namely regulatory T cells that express FOXP3 transcription factor. Since IL-12 and IL-18 mediate inflammatory response and Tregs exhibit anti-inflammatory potential, we aimed to examine their reciprocal relationship in patients with type 1 diabetes. The study group consisted of 47 children diagnosed with type 1 diabetes and 28 healthy individuals. Serum levels of IL-12 and IL-18 were measured by ELISA, and the peripheral blood CD4⁺CD25^high FOXP3⁺ regulatory T cell frequencies were analyzed by flow cytometry. Patients with type 1 diabetes had a decreased percentage of circulating CD4⁺CD25^highFOXP3⁺ Tregs in comparison to their healthy counterparts. In addition, they produced more IL-12 and IL-18 than children from the control group. Concentrations of these cytokines positively correlated with one another, as well as with CRP and HbA1c. Moreover, the negative association between IL-12, IL-18, CRP serum levels, and the frequency of regulatory CD4⁺CD25^highFOXP3⁺ Tregs was observed. IL-12 and IL-18 may have direct or indirect impact on regulatory T cell subset, which may contribute to their reduced frequency in peripheral blood of patients with type 1 diabetes mellitus.

Heterogeneity of Tregs and the complexity in the IL-12 cytokine family signaling in driving T-cell immune responses in atherosclerotic vessels

The importance of immune inflammation in the development and progression of atherosclerotic lesions is well recognized. Accumulated evidence shows striking features of heterogeneity of regulatory T cells (Tregs) and the importance of the IL-12 cytokine family in regulation of Tregs in atherogenesis. The present review briefly summarized the current knowledge about the impact of the IL-12 cytokine family in regulation of immune processes in atherogenesis.

The selective impact of transgenically expressed glucocorticoid receptor on T cells

Glucocorticoids (GCs) strongly impact on different T cell subsets inducing generally immunosuppressive effects, whereas much less is known about the effect of GC on natural killer (NK) cells. The aims of this study were to investigate the effects of GC on T cell functions, including T cell-mediated anti-tumor immune response, and on NK cells. We have used lck-GR mice, which overexpress a transgenic rat GR in both T and NK cells. These mice were found to have decreased both CD4(+) and CD8(+) T cell populations in the periphery. In contrast, both NK and NKT cells were found in normal numbers in lck-GR mice. To identify genes and pathways affected by GR overexpression in our system in T cells, we have compared gene expression profiles in wild-type and lck-GR T cells. Among the genes upregulated in T cells from lck-GR mice, the microarray analysis has identified genes regulating expansion of regulatory T cells. The analysis of genes downregulated in lck-GR mice has identified genes and gene associated with the regulation of immune response. With regard to the effects on T cell functions in lck-GR mice, transgenic expression of GR had a suppressive effect on killer cell activity in vitro. In addition, lck-GR mice showed an increased tumor growth in murine tumor model in vivo, which may be a possible consequence of reduced T cell numbers and activity. We conclude that an increased expression of the GR strongly affects numbers and possibly functions of T cell subsets, but has little effect on NK cells.

Interleukin-12 (IL-12p70) Promotes Induction of Highly Potent Th1-Like CD4(+)CD25(+) T Regulatory Cells That Inhibit Allograft Rejection in Unmodified Recipients

In rat models, CD4(+)CD25(+) T regulatory cells (Treg) play a key role in the induction and maintenance of antigen-specific transplant tolerance, especially in DA rats with PVG cardiac allografts (1, 2). We have previously described generation of alloantigen-specific Treg (Ts1), by culture of naïve natural CD4(+)CD25(+) Treg (nTreg) with specific alloantigen and IL-2 for 4 days. These cells express mRNA for IFN-γ receptor (ifngr) and suppress donor but not third party cardiac allograft rejection mediated by alloreactive CD4(+) T cells at ratios of <1:10. Here, we show that Ts1 also expressed the IL-12p70 specific receptor (il-12rβ2) and that rIL-12p70 can induce their proliferation. Ts1 cells re-cultured with rIL-12p70 alone or rIL-12p70 and recombinant interleukin-2 (rIL-2), suppressed proliferation of CD4(+) T cells in mixed lymphocyte culture at <1:1024, whereas Ts1 cells re-cultured with rIL-2 and alloantigen only suppressed at 1:32-64. The rIL-12p70 alloactivated Ts1 cells markedly delayed PVG, but not third party Lewis, cardiac allograft rejection in normal DA recipients. Ts1 cells re-cultured for 4 days with rIL-12p70 alone, but not those re-cultured with rIL-12p70 and rIL-2, expressed more il-12rβ2, t-bet, and ifn-γ, and continued to express the markers of Ts1 cells, foxp3, ifngr, and il-5 indicating Th1-like Treg were induced. Ts1 cells re-cultured with rIL-2 and alloantigen remained of the Ts1 phenotype and did not suppress cardiac graft rejection in normal DA rats. We induced highly suppressive Th1-like Treg from naïve nTreg in 7 days by culture with alloantigen, first with rIL-2 then with rIL-12p70. These Th1-like Treg delayed specific donor allograft rejection demonstrating therapeutic potential.

IL-12hi rapamycin-conditioned dendritic cells mediate IFN-γ-dependent apoptosis of alloreactive CD4+ T cells in vitro and reduce lethal graft-versus-host disease

Rapamycin (RAPA) inhibits the mechanistic target of rapamycin (mTOR), a crucial immune system regulator. Dendritic cells (DC) generated in RAPA (RAPA-DC) enrich for CD4(+) forkhead box p3 (FoxP3(+)) regulatory T cells and induce T cell apoptosis by an unknown mechanism. RAPA-DC also promote experimental allograft survival, yet paradoxically secrete increased IL-12, crucial for the generation of IFN-γ(+) CD4(+) T cells. However, IFN-γ is pro-apoptotic and IL-12-driven IFN-γ inhibits experimental graft-versus-host disease (GVHD). We hypothesized that IL-12(hi) RAPA-DC would facilitate IFN-γ-mediated apoptosis of alloreactive T cells and, unlike control (CTR)-DC, would reduce lethal GVHD. Following LPS stimulation, RAPA-DC exhibited decreased MHCII and co-stimulatory molecules and contained a significant population of CD86(lo) IL-12(hi) cells. Consistent with our hypothesis, both unstimulated and LPS-stimulated RAPA-DC enhanced alloreactive CD4(+) T cell apoptosis in culture. Augmented T cell apoptosis was ablated by IFN-γ neutralization or using T cells lacking the IFN-γ receptor, and it was associated with increased expression of Fas and cleaved caspase 8. DC production or responses to IFN-γ were not important to increased apoptotic functions of RAPA-DC. LPS-stimulated IL-12p40(-/-) RAPA-DC induced lower levels of T cell apoptosis in culture, which was further decreased with addition of anti-IFN-γ. Finally, whereas CTR-DC accelerated mortality from GVHD, LPS-treated RAPA-DC significantly prolonged host survival. In conclusion, increased apoptosis of allogeneic CD4(+) T cells induced by LPS-stimulated IL-12(hi) RAPA-DC is mediated in vitro through IFN-γ and in part by increased IL-12 expression. Enhanced production of IL-12, the predominant inducer of IFN-γ by immune cells, is a probable mechanism underlying the capacity of LPS-treated RAPA-DC to reduce GVHD.

Do Natural T Regulatory Cells become Activated to Antigen Specific T Regulatory Cells in Transplantation and in Autoimmunity?

Antigen specific T regulatory cells (T_reg) are often CD4⁺CD25⁺FoxP3⁺ T cells, with a phenotype similar to natural T_reg (nT_reg). It is assumed that nT_reg cannot develop into an antigen specific T_reg as repeated culture with IL-2 and a specific antigen does not increase the capacity or potency of nT_reg to promote immune tolerance or suppress in vitro. This has led to an assumption that antigen specific T_reg mainly develop from CD4⁺CD25⁻FoxP3⁻ T cells, by activation with antigen and TGF-β in the absence of inflammatory cytokines such as IL-6 and IL-1β. Our studies on antigen specific CD4⁺CD25⁺ T cells from animals with tolerance to an allograft, identified that the antigen specific and T_reg are dividing, and need continuous stimulation with specific antigen T cell derived cytokines. We identified that a variety of cytokines, especially IL-5 and IFN-γ but not IL-2 or IL-4 promoted survival of antigen specific CD4⁺CD25⁺FoxP3⁺ T_reg. To examine if nT_reg could be activated to antigen specific T_reg, we activated nT_reg in culture with either IL-2 or IL-4. Within 3 days, antigen specific T_reg are activated and there is induction of new cytokine receptors on these cells. Specifically nT_reg activated by IL-2 and antigen express the interferon-γ receptor (IFNGR) and IL-12p70 (IL-12Rβ2) receptor but not the IL-5 receptor (IL-5Rα). These cells were responsive to IFN-γ or IL-12p70. nT_reg activated by IL-4 and alloantigen express IL-5Rα not IFNGR or IL-12p70Rβ2 and become responsive to IL-5. These early activated antigen specific T_reg, were respectively named Ts1 and Ts2 cells, as they depend on Th1 or Th2 responses. Further culture of Ts1 cells with IL-12p70 induced Th1-like T_reg, expressing IFN-γ, and T-bet as well as FoxP3. Our studies suggest that activation of nT_reg with Th1 or Th2 responses induced separate lineages of antigen specific T_reg, that are dependent on late Th1 and Th2 cytokines, not the early cytokines IL-2 and IL-4.

Regulation of immunological balance by sustained interferon-γ gene transfer for acute phase of atopic dermatitis in mice

Interferon (IFN)-γ, a potent T helper 1 (Th1) cell cytokine, is suggested to suppress Th2 cell responses. Here, we aimed to investigate whether pCpG-Muγ, a plasmid continuously expressing murine IFN-γ, is an effective treatment of atopic dermatitis, a Th2-dominant skin disease. Nishiki-nezumi Cinnamon/Nagoya (NC/Nga) atopic mice with early dermatitis were transfected with pCpG-Muγ by a hydrodynamic tail vein injection at a dose of 0.05 or 0.2 pmol per mouse. The skin lesions improved only in mice receiving the high dose of pCpG-Muγ. IFN-γ gene transfer resulted in a high mRNA expression of IFN-γ and interleukin (IL)-12 and regulatory T cell (Treg) related cytokines, such as IL-10 and transforming growth factor-β, in the spleen, whereas it reduced the IL-4 mRNA expression, and serum levels of immunoglobulin (Ig) G1 and IgE. In addition, the gene transfer markedly inhibited the epidermal thickening, infiltration of inflammatory cells into the skin, the occurrence of dry skin and pruritus. No exacerbating effect on the Th1-mediated contact dermatitis was observed after IFN-γ gene transfer. Taken together, these results indicate that sustained IFN-γ gene transfer induced polarized Th1 immunity under Th2-dominant conditions in NC/Nga mice, leading to an improvement in the symptoms of acute atopic dermatitis without adverse side effects.

Intravenous tolerance effectively overcomes enhanced pro-inflammatory responses and experimental autoimmune encephalomyelitis severity in the absence of IL-12 receptor signaling

Intravenous (i.v.) administration of autoantigen effectively induces Ag-specific tolerance against experimental autoimmune encephalomyelitis (EAE). We and others have shown enhanced EAE severity in mice lacking IL-12 or its receptor, strongly suggesting an immunoregulatory effect of IL-12 signaling. To examine the role of IL-12 responsiveness in autoantigen-induced tolerance in EAE, we administered autoantigen i.v. in two distinct treatment regimes to wildtype and IL-12Rβ2(-/-) mice, immunized to develop EAE. Administration at the induction phase suppressed EAE in wildtype and IL-12Rβ2(-/-) mice however the effect was somewhat less potent in the absence of IL-12Rβ2. Expression of pro-inflammatory cytokines such as IFN-γ, IL-17 and IL-2, was inhibited in wild-type tolerized mice but less so in IL-12Rβ2(-/-) mice. I.v. antigen was also effective in suppressing disease in both genotypes when given during the clinical phase of disease with similar CNS inflammation, demyelination and peripheral inflammatory cytokine profiles observed in both genotypes. There was however a mild impact of a lack of IL-12 signaling on Treg induction during tolerance induction compared to WT mice in this treatment regime. These findings show that the enhanced severity of EAE that occurs in the absence of IL-12 signaling can be effectively overcome by i.v. autoantigen, indicating that this therapeutic effect is not primarily mediated by IL-12 and that i.v. tolerance could be a powerful approach in suppressing severe and aggressive MS.

Prevalence, distribution and functional significance of the -237C to T polymorphism in the IL-12Rβ2 promoter in Indian tuberculosis patients

Cytokine/cytokine receptor gene polymorphisms related to structure/expression could impact immune response. Hence, the −237 polymorphic site in the 5′ promoter region of the IL-12Rβ2 (SNP ID: rs11810249) gene associated with the AP-4 transcription motif GAGCTG, was examined. Amplicons encompassing the polymorphism were generated from 46 pulmonary tuberculosis patients, 35 family contacts and 28 miscellaneous volunteers and sequenced. The C allele predominated among patients, (93.4%, 43/46), and in all volunteers and contacts screened, but the T allele was exclusively limited to patients, (6.5%, 3/46). The functional impact of this polymorphism on transcriptional activity was assessed by Luciferase-reporter and electrophoretic mobility shift assays (EMSA). Luciferase-reporter assays showed a significant reduction in transcriptional efficiency with T compared to C allele. The reduction in transcriptional efficiency with the T allele construct (pGIL-12Rb2-T), in U-87MG, THP-1 and Jurkat cell lines, were 53, 37.6, and 49.8% respectively, compared to the C allele construct (pGIL-12Rb2-C). Similarly, densitometric analysis of the EMSA assay showed reduced binding of the AP-4 transcription factor, to T compared to the C nucleotide probe. Reduced mRNA expression in all patients (3/3) harboring the T allele was seen, whereas individuals with the C allele exhibited high mRNA expression (17/25; 68%, p = 0.05). These observations were in agreement with the in vitro assessment of the promoter activity by Luciferase-reporter and EMSA assays. The reduced expression of IL-12Rβ2 transcripts in 8 patients despite having the C allele was attributed to the predominant over expression of the suppressors (IL-4 and GATA-3) and reduced expression of enhancers (IFN-α) of IL-12Rβ2 transcripts. The 17 high IL-12Rβ2 mRNA expressers had significantly elevated IFN-α mRNA levels compared to low expressers and volunteers. Notwithstanding the presence of high levels of IL-12Rβ2 mRNA in these patients elevated IFN-α expression could modulate their immune responses to Mycobacterium tuberculosis.

Distinct regulatory CD4+T cell subsets; differences between naïve and antigen specific T regulatory cells

Effector T cells have functional subpopulations with distinct cytokine, cytokine receptor, chemokine receptor and transcription factors. We review how activation of antigen specific Treg induces expression of cytokines, cytokine receptors and chemokine receptors depending upon the effector lineage they are activated by. Activated Treg express receptors that are directly related to the effector T cell lineage. Other classes of Treg are induced in the periphery from effector lineage CD4(+)CD25(-)FOXP3(-)CD127(high)T cells, either by IL-10 or TGF-β or by association with activated CD4(+)CD25(+)FOXP3(+)Treg. Thus Treg are produced and adapt to the specific immune inflammatory environment they are activated within. Activated Treg produce different molecules to mediate suppression, which are tailored to the immune response they are activated by and control.

Cytokine-induced alterations of α7 nicotinic receptor in colonic CD4 T cells mediate dichotomous response to nicotine in murine models of Th1/Th17- versus Th2-mediated colitis

Ulcerative colitis (UC) and Crohn's disease (CD) are two forms of chronic inflammatory bowel disease. CD4 T cells play a central role in the pathogenesis of both diseases. Smoking affects both UC and CD but with opposite effects, ameliorating UC and worsening CD. We hypothesized that the severity of gut inflammation could be modulated through T cell nicotinic acetylcholine receptors (nAChRs) and that the exact clinical outcome would depend on the repertoire of nAChRs on CD4 T cells mediating each form of colitis. We measured clinical and immunologic outcomes of treating BALB/c mice with oxazolone- and trinitrobenzene sulfonic acid (TNBS)-induced colitides by nicotine. Nicotine attenuated oxazolone colitis, which was associated with an increased percentage of colonic regulatory T cells and a reduction of Th17 cells. TCR stimulation of naive CD4(+)CD62L(+) T cells in the presence of nicotine upregulated expression of Foxp3. In marked contrast, nicotine worsened TNBS colitis, and this was associated with increased Th17 cells among colonic CD4 T cells. Nicotine upregulated IL-10 and inhibited IL-17 production, which could be abolished by exogenous IL-12 that also abolished the nicotine-dependent upregulation of regulatory T cells. The dichotomous action of nicotine resulted from the up- and downregulation of anti-inflammatory α7 nAChR on colonic CD4 T cells induced by cytokines characteristic of the inflammatory milieu in oxazolone (IL-4) and TNBS (IL-12) colitis, respectively. These findings help explain the dichotomous effect of smoking in patients with UC and CD, and they underscore the potential for nicotinergic drugs in regulating colonic inflammation.

Stat4 is critical for the balance between Th17 cells and regulatory T cells in colitis

Th17 play a central role in autoimmune inflammatory responses. Th1 are also necessary for autoimmune disease development. The interplay of Th1 signals and how they coordinate with Th17 during inflammatory disease pathogenesis are incompletely understood. In this study, by adding Stat4 deficiency to Stat6/T-bet double knockout, we further dissected the role of Stat4 in Th1 development and colitis induction. We showed that in the absence of the strong Th2 mediator Stat6, neither Stat4 nor T-bet is required for IFN-γ production and Th1 development. However, addition of Stat4 deficiency abolished colitis induced by Stat6/T-bet double-knockout cells, despite Th1 and Th17 responses. The failure of colitis induction by Stat4/Stat6/T-bet triple-knockout cells is largely due to elevated Foxp3(+) regulatory T cell (Treg) development. These results highlight the critical role of Stat4 Th1 signals in autoimmune responses in suppressing Foxp3(+) Treg responses and altering the balance between Th17 and Tregs to favor autoimmune disease.

Programmed death 1 and cytokine inducible SH2-containing protein dependent expansion of regulatory T cells upon stimulation With Mycobacterium tuberculosis

We previously found that CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) expand in response to Mycobacterium tuberculosis infection in individuals who are healthy tuberculin reactors, but not in tuberculin-negative individuals. We also found that the M. tuberculosis mannose-capped lipoarabinomannan and prostaglandin E2 produced by monocytes are involved in Treg expansion. In this study, we found that Tregs expanded from CD4(+)CCR4(+) cells but not from CCR4(-) cells. However, introduction of CCR4 small interfering RNA (siRNA) into CD4(+) cells only marginally reduced expansion of Tregs. Using siRNA and neutralizing antibodies, we found that expansion of Tregs by M. tuberculosis required expression of programmed death1 (PD-1) and expression of the signaling molecule, cytokine inducible SH2-containing protein (CISH). Anti-PD-1 siRNA inhibited expression of CISH by expanded Tregs. M. tuberculosis-expanded Tregs produced transforming growth factor β and interleukin 10 and reduced the frequency of interferon γ-producing autologous CD8(+) cells. We conclude that M. tuberculosis infection induces development of Tregs from CCR4(+) cells through a process that depends on PD-1and CISH.

3G11 expression in CD4+ T cell-mediated autoimmunity and immune tolerance

3G11 is a sialylated carbohydrate epitope of the disialoganglioside molecule expressed on mouse CD4(+) T cells. Recent research showed that 3G11 expression is related to the modulation of T cell function, i.e., 3G11(-) T cells exhibit anergic/Treg characteristics and efficiently inhibit autoimmunity in the central nervous system. The relationship between 3G11 expression and immune tolerance is summarized in this literature review.

Disturbances in some gene expression in T regulatory cells separated from children with metabolic syndrome

The metabolic syndrome (MS) is defined as a cluster of risk factors, including abdominal obesity, dyslipidaemia, glucose intolerance and hypertension, which increase the risk for coronary heart disease. The immunological aspects of obesity and MS, including the role of T regulatory cells, have been intensively investigated. The aim of this study was to determine whether there is any disturbance in T regulatory cells number and/or function in children with MS. The percentages of T regulatory cells in the peripheral blood of children fulfilling the International Diabetes Federation criteria of the disease (n = 47) were assessed. Treg cells were also separated for further analysis of multiple genes important in their function with the use of real-time RT-PCR. We did not observe any difference in Treg percentages between study and control group but there was lower expression of some molecules including transforming growth factor-beta and interleukin-12 family members in Treg cells separated from children with MS compared to the healthy subjects. Our study is the first to report significant disturbances in some gene expression in T regulatory cells separated from children with MS. The results should be useful for further research in this field, including immunotherapeutic interventions.

mTOR and GSK-3 shape the CD4+ T-cell stimulatory and differentiation capacity of myeloid DCs after exposure to LPS

Prolonged inhibition of the kinase, mammalian target of rapamycin (mTOR), during myeloid dendritic cell (DC) generation confers resistance to maturation. Recently, however, mTOR inhibition immediately before Toll-like receptor ligation has been found to exert proinflammatory effects on myeloid cells, notably enhanced IL-12p40/p70 production. We show, for the first time, that mouse or human DCs generated under mTOR inhibition exhibit markedly enhanced IL-12p70 production after lipopolysaccharide (LPS) stimulation, despite impaired costimulatory molecule expression and poor T-cell stimulatory ability. Consistent with this finding, we reveal that increased IL-12p40 production occurs predominantly in CD86(lo) immature DCs. High IL-12p40/p70 production by CD86(lo) DC resulted from failed down-regulation of glycogen synthase kinase-3 (GSK-3) activity and could not be ascribed to enhanced Akt function. Despite high IL-12p70 secretion, rapamycin-conditioned, LPS-stimulated DCs remained poor T-cell stimulators, failing to enhance allogeneic Th1 cell responses. We also report that inhibition of GSK-3 impedes the ability of LPS-stimulated DCs to induce forkhead box p3 in CD4(+)CD25(-) T cells, as does the absence of IL-12p40/p70. Thus, GSK-3 activity in DC is regulated via signaling linked to mTOR and modulates their capacity both to produce IL-12p40/p70 and induce forkhead box p3 in CD4(+) T cells under inflammatory conditions.

The genetics of Crohn's disease

From epidemiological data, based on concordance data in family studies, via linkage analysis to genome-wide association studies, we and others have accumulated robust evidence implicating more than 30 distinct genomic loci involved in the genetic susceptibility to Crohn's disease (CD). These loci encode genes involved in a number of homeostatic mechanisms: innate pattern recognition receptors (NOD2/CARD15, TLR4, CARD9), the differentiation of Th17-lymphocytes (IL-23R, JAK2, STAT3, CCR6, ICOSLG), autophagy (ATG16L1, IRGM, LRRK2), maintenance of epithelial barrier integrity (IBD5, DLG5, PTGER4, ITLN1, DMBT1, XBP1), and the orchestration of the secondary immune response (HLA-region, TNFSF15/TL1A, IRF5, PTPN2, PTPN22, NKX2-3, IL-12B, IL-18RAP, MST1). While many of these loci also predispose to pediatric CD, an additional number of childhood-onset loci have been identified recently (e.g., TNFRSF6B). Not only has the identification of these loci improved our understanding of the pathophysiology of CD, this knowledge also holds real promise for clinical practice.

Comparative ability of IL-12 and IL-28B to regulate Treg populations and enhance adaptive cellular immunity

Improving the potency of immune responses is paramount among issues concerning vaccines against deadly pathogens. IL-28B belongs to the newly described interferon lambda (IFNlambda) family of cytokines, and has not yet been assessed for its potential ability to influence adaptive immune responses or act as a vaccine adjuvant. We compared the ability of plasmid-encoded IL-28B to boost immune responses to a multiclade consensus HIV Gag plasmid during DNA vaccination with that of IL-12. We show here that IL-28B, like IL-12, is capable of robustly enhancing adaptive immunity. Moreover, we describe for the first time how IL-28B reduces regulatory T-cell populations during DNA vaccination, whereas IL-12 increases this cellular subset. We also show that IL-28B, unlike IL-12, is able to increase the percentage of splenic CD8(+) T cells in vaccinated animals, and that these cells are more granular and have higher antigen-specific cytolytic degranulation compared with cells taken from animals that received IL-12 as an adjuvant. Lastly, we report that IL-28B can induce 100% protection from mortality after a lethal influenza challenge. These data suggest that IL-28B is a strong candidate for further studies of vaccine or immunotherapy protocols.