The Family of IL-10-secreting CD4+ T cells

Adipose Tissue-Derived Mesenchymal Stem Cells Attenuate Staphylococcal Enterotoxin A-Induced Toxic Shock

Adipose tissue-derived stem cells (ASCs), which are mesenchymal stromal cells isolated from adipose tissues, exhibit immunomodulatory effects that are promising for several applications, including the therapeutics of inflammatory diseases. In the present study, the effect of ASCs on bacterial toxin-induced inflammation was investigated. Intraperitoneal administration of ASCs rescued mice from lethal shock induced by staphylococcal enterotoxin A (SEA) potentiated with lipopolysaccharide. In the sera and/or spleens of mice administered ASCs, the production of proinflammatory cytokines, including interferon gamma, tumor necrosis factor alpha, interleukin-6 (IL-6), and IL-2 was reduced. By quantitative real-time PCR, the expression of Foxp3 in the mice administered ASCs was not altered. On the other hand, the expression of IL-12 receptor and STAT4 was decreased with ASC administration. These results imply that the effect of ASCs is not involved in the lineage of regulatory T cells but that these cells may modulate TH1 differentiation. This information provides evidence that ASCs have properties that are effective to attenuate SEA-induced toxic shock and should prompt further exploration on other inflammatory diseases caused by bacterial toxins or bacterial infections.

A B-1a cell subset induces Foxp3(-) T cells with regulatory activity through an IL-10-independent pathway

Regulatory T (Treg) cells play a critical role in the maintenance of tolerance. B-1a cells belong to a specific and functionally important B-cell subset that exerts its regulatory role through the production of IL-10. While IL-10 has been correlated with the induction of type 1 Treg (Tr1) cells or Tr1-like cells, whether IL-10-producing B-1a cells are able to induce Treg cells, especially the Tr1 lineage, is poorly understood. We have demonstrated that, similar to the reported B-2 cells, B-1a cells are able to convert naïve CD4(+)CD25(-) T cells into a subset of T cells with suppressive function, which we called 'Treg-of-B1a' cells. Treg-of-B1a cells do not express Foxp3, but upregulate the Treg markers OX40, programmed death 1 (PD-1), inducible costimulator (ICOS) and IL-10R. Moreover, Treg-of-B1a cells do not express Foxp3 and produce high levels of IFN-γ and IL-10, but minimal amounts of IL-4; therefore, they resemble Tr1 cells. However, utilizing IL-10(-/-) mice, we showed that IL-10 was not involved in the induction of Treg-of-B1a cells. On the contrary, CD86-mediated costimulation was essential for B-1a cells to drive the induction of Treg-of-B1a cells. Finally, we demonstrated that, in contrast to the Treg cells generated by B-2 cells that mediate contact-dependent suppression, Treg-of-B1a cells suppress through secreting soluble factors. While Tr1 cells mediate suppression mainly through IL-10 or TGF-β secretion, Treg-of-B1a cells mediate suppression through an IL-10- and TGF-β-independent pathway. Together, these findings suggest that B-1a cells induce a functionally and phenotypically distinct Treg population that is dissimilar to the reported Foxp3(+) Treg or Tr1 cells.

IL-10 and ARG-1 concentrations in bone marrow and peripheral blood of metastatic neuroblastoma patients do not associate with clinical outcome

The expression of the immunosuppressive molecules IL-10 and arginase 1 (ARG-1), and of FOXP3 and CD163, as markers of regulatory T cells (Treg) and macrophages, respectively, was evaluated in bone marrow (BM) and peripheral blood (PB) samples collected at diagnosis from patients with metastatic neuroblastoma (NB). IL-10 and ARG-1 plasma concentrations were measured and the association of each parameter with patients' outcome was tested. The percentages of immunosuppressive Treg and type-1 regulatory (Tr1) cells were also determined. In both BM and PB samples, IL-10 mRNA expression was higher in metastatic NB patients than in controls. IL-10 plasma concentration was higher in patients with NB regardless of stage. Neither IL-10 expression nor IL-10 plasma concentration significantly associated with patient survival. In PB samples from metastatic NB patients, ARG-1 and CD163 expression was higher than in controls but their expression did not associate with survival. Moreover, ARG-1 plasma concentration was lower than in controls, and no association with patient outcome was found. Finally, in metastatic NB patients, the percentage of circulating Treg was higher than in controls, whereas that of Tr1 cells was lower. In conclusion, although IL-10 concentration and Treg percentage were increased, their contribution to the natural history of metastatic NB appears uncertain.

Central nervous system infiltrates are characterized by features of ongoing B cell-related immune activity in MP4-induced experimental autoimmune encephalomyelitis

In multiple sclerosis (MS) lymphoid follicle-like aggregates have been reported in the meninges of patients. Here we investigated the functional relevance of B cell infiltration into the central nervous system (CNS) in MP4-induced experimental autoimmune encephalomyelitis (EAE), a B cell-dependent mouse model of MS. In chronic EAE, B cell aggregates were characterized by the presence of CXCL13(+) and germinal center CD10(+) B cells. Germline transcripts were expressed in the CNS and particularly related to TH17-associated isotypes. We also observed B cells with restricted VH gene usage that differed from clones found in the spleen. Finally, we detected CNS-restricted spreading of the antigen-specific B cell response towards a myelin and a neuronal autoantigen. These data imply the development of autonomous B cell-mediated autoimmunity in the CNS in EAE - a concept that might also apply to MS itself.

Cannabidiol, a non-psychoactive cannabinoid, leads to EGR2-dependent anergy in activated encephalitogenic T cells

Background

Cannabidiol (CBD), the main non-psychoactive cannabinoid, has been previously shown by us to ameliorate clinical symptoms and to decrease inflammation in myelin oligodendrocyte glycoprotein (MOG)35-55-induced mouse experimental autoimmune encephalomyelitis model of multiple sclerosis as well as to decrease MOG35-55-induced T cell proliferation and IL-17 secretion. However, the mechanisms of CBD anti-inflammatory activities are unclear.

Methods

Here we analyzed the effects of CBD on splenocytes (source of accessory T cells and antigen presenting cells (APC)) co-cultured with MOG35-55-specific T cells (T_MOG) and stimulated with MOG35-55. Using flow cytometry, we evaluated the expression of surface activation markers and inhibitory molecules on T cells and B cells. T_MOG cells were purified using CD4 positive microbead selection and submitted for quantitative PCR and microarray of mRNA transcript analyzes. Cell signaling studies in purified T_MOG were carried out using immunoblotting.

Results

We found that CBD leads to upregulation of CD69 and lymphocyte-activation gene 3 (LAG3) regulatory molecules on CD4⁺CD25⁻ accessory T cells. This subtype of CD4⁺CD25⁻CD69⁺LAG3⁺ T cells has been recognized as induced regulatory phenotype promoting anergy in activated T cells. Indeed, we observed that CBD treatment results in upregulation of EGR2 (a key T cell anergy inducer) mRNA transcription in stimulated T_MOG cells. This was accompanied by elevated levels of anergy promoting genes such as IL-10 (anti-inflammatory cytokine), STAT5 (regulatory factor), and LAG3 mRNAs, as well as of several enhancers of cell cycle arrest (such as Nfatc1, Casp4, Cdkn1a, and Icos). Moreover, CBD exposure leads to a decrease in STAT3 and to an increase in STAT5 phosphorylation in T_MOG cells, positive and negative regulators of Th17 activity, respectively. In parallel, we observed decreased levels of major histocompatibility complex class II (MHCII), CD25, and CD69 on CD19⁺ B cells following CBD treatment, showing diminished antigen presenting capabilities of B cells and reduction in their pro-inflammatory functions.

Conclusions

Our data suggests that CBD exerts its immunoregulatory effects via induction of CD4⁺CD25⁻CD69⁺LAG3⁺ cells in MOG35-55-activated APC/T_MOG co-cultures. This is accompanied by EGR2-dependent anergy of stimulated T_MOG cells as well as a switch in their intracellular STAT3/STAT5 activation balance leading to the previously observed decrease in Th17 activity.

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.

Short-term effect of high-dose vitamin D on the level of interleukin 10 in patients with multiple sclerosis: a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. Vitamin D has been related to the prevention of MS and to modulating its course. Recent studies have shown the safety of high-dose vitamin D in MS.

OBJECTIVE

This study compared the effects of high-dose vitamin D on interleukin 10 (IL-10) levels in MS patients in a double-blind, randomized clinical trial.

METHODS

Ninety-four patients with relapsing remitting MS (RRMS) were randomized into a treatment and a placebo group. Both groups received conventional MS treatment. The intervention group received 50,000 IU of vitamin D every 5 days for 3 months. IL-10 was measured at baseline and after 3 months.

RESULTS

Serum levels of IL-10 were (median ± IQR): 12.58 ± 11.97 and 10.97 ± 9.97 pg/ml in the intervention and placebo groups, respectively, at baseline (p = 0.161); after 3 months, these levels were 13.76 ± 18.95 and 11.31 ± 19.63 pg/ml, respectively (p = 0.158). The IL-10 level increased significantly after receiving high-dose vitamin D for 3 months (β = 0.737, p = 0.015 and R2 = 0.91).

CONCLUSION

IL-10 levels increased significantly in RRMS patients after taking high-dose vitamin D3 for 3 months. High-dose vitamin D might be useful in promoting an anti-inflammatory state in RRMS patients.

Photoimmunology and Multiple Sclerosis

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is best known for its ability to cause skin cancer, it is also associated with protection against a range of autoimmune diseases, particularly multiple sclerosis (MS). Although the precise mechanism by which sunlight affords protection from MS remains to be determined, some have hypothesised that UV immunosuppression explains the "latitude-gradient effect" associated with MS. By stimulating the release of soluble factors in exposed skin, UV activates immune suppressive pathways that culminate in the induction of regulatory cells in distant tissues. Each and every one of the immune suppressive cells and molecules activated by UV exposure are potential targets for treating and preventing MS. A thorough understanding of the mechanisms involved is therefore required if we are to realise the therapeutic potential of photoimmunology.

Co-stimulation with TNF receptor superfamily 4/25 antibodies enhances in-vivo expansion of CD4+CD25+Foxp3+ T cells (Tregs) in a mouse study for active DNA Aβ42 immunotherapy

The study was designed to test DNA Aβ42 immunization in mice as alternative approach for possible active immunotherapy in Alzheimer patients. As results, we found polarized Th2 immune responses, efficient Aβ42 antibody levels, and disappearance of antigen specific T cells. In-vivo TNFRSF4/25 antibody co-stimulation enhanced Aβ42 specific T cell responses with initial Th2 expansion and subsequent development of Aβ42 specific CD4+CD25+Foxp3+ cells. It showed that Th2 biased responses due to gene gun immunizations propagate the development of regulatory T cells. In conclusion, full-length DNA Aβ42 immunization into skin results in a regulatory response with minimal risk of inflammation and autoimmunity.

T follicular helper cells and HIV/SIV-specific antibody responses

PURPOSE OF REVIEW

Here, we describe recent data on the characterization of follicular helper CD4 T cells (Tfh) and the dynamics of Tfh-B-cell interactions in HIV and simian immunodeficiency virus (SIV) infection and discuss important aspects of these interactions that need to be addressed in order to design more effective vaccines that elicit broadly neutralizing antibodies.

RECENT FINDINGS

Mouse, nonhuman primate (NHP) and human Tfh cells share phenotypic, functional and molecular programs, which are regulated by local signals and spatiotemporal parameters. Chronic HIV/SIV infection results in accumulation of Tfh, germinal center B cells and circulating virus-specific immunoglobulins in some individuals. However, most HIV/SIV-infected individuals do not mount broadly neutralizing antibodies, pointing to functional defects in Tfh cells in chronic HIV/SIV infection. The susceptibility of particular CD4 T-cell populations to HIV/SIV infection within lymph nodes notably impacts upon the dynamics of Tfh-germinal center B-cell interactions. Some circulating CD4 T cells share certain characteristics with Tfh cells, however, their direct origin from germinal center Tfh cells is not clear.

SUMMARY

There are many ways in which HIV and SIV influence the complex signals and mechanisms regulating the development of Tfh cells and their interactions with germinal center B cells. Understanding the biology of Tfh cells will be necessary to appropriately recruit these cells during vaccination with the goal of stimulating a more broad and potent neutralizing antibody response.

Lymphocytes and autoimmunity after spinal cord injury

Over the past 15 years an immense amount of data has accumulated regarding the infiltration and activation of lymphocytes in the traumatized spinal cord. Although the impact of the intraspinal accumulation of lymphocytes is still unclear, modulation of the adaptive immune response via active and passive vaccination is being evaluated for its preclinical efficacy in improving the outcome for spinal-injured individuals. The complexity of the interaction between the nervous and the immune systems is highlighted in the contradictions that appear in response to these modulations. Current evidence regarding augmentation and inhibition of the adaptive immune response to spinal cord injury is reviewed with an aim toward reconciling conflicting data and providing consensus issues that may be exploited in future therapies. Opportunities such an approach may provide are highlighted as well as the obstacles that must be overcome before such approaches can be translated into clinical trials.

Decreased percentage of CD4(+)Foxp3(+)TGF-β(+) and increased percentage of CD4(+)IL-17(+) cells in bronchoalveolar lavage of asthmatics

Background

Asthma is a chronic inflammatory disorder of the airways with the proven role of Th2 cells in its pathogenesis. The role and characteristic of different subsets of CD4⁺ cells is much less known.

Aim

The aim of the study was to analyze the incidence of different subsets of CD4⁺ T cells, in particular different subsets of CD4⁺ cells with the co-expression of different cytokines.

Methods

Twenty five stable asthmatic and twelve age-matched control subjects were recruited to the study. Bronchoscopy and bronchoalveolar lavage (BAL) were performed in all study subjects. CD4⁺ T cells were isolated from BAL fluid by positive magnetic selection. After stimulation simultaneous expression of TGF-β, FoxP3, CD25, IFN-γ, IL-4, TNF-α (set 1); IL-10, FoxP3, CD25, IFN-γ, IL-4, MIP-1β (set 2); IL-17A, IL-8, IFN-γ, IL-4, MIP-1β (set 3) were measured by flow cytometry.

Results

The percentage of CD4⁺ cells co-expressing Foxp3 and TGF-β (CD4⁺Foxp3⁺TGF-β⁺ cells) was significantly lower (P = 0.03), whereas the percentage of CD4⁺IL-17⁺ cells (P = 0.008), CD4⁺IL-17⁺ IFN-γ⁺ cells (P = 0.047) and CD4⁺IL-4⁺ cells (P = 0.01) were significantly increased in asthmatics compared with that seen in healthy subjects. A significantly higher percentage of CD4⁺Foxp3⁺ cells from asthma patients expressed IFN-γ (P = 0.01), IL-4 (P = 0.004) and CD25 (P = 0.04), whereas the percentage of CD4⁺IL-10⁺ cells expressing Foxp3 was significantly decreased in asthmatics (P = 0.03). FEV₁% predicted correlated negatively with the percentage of CD4⁺IL-17⁺ cells (r = -0.33; P = 0.046) and positively with CD4⁺Foxp3⁺TGF-β⁺ cells (r = 0.43; P = 0.01).

Conclusions

Our results suggest that in the airways of chronic asthma patients there is an imbalance between increased numbers of CD4⁺IL-17⁺ cells and Th2 cells and decreased number of CD4⁺Foxp3⁺TGF-β⁺.

Vitamin D reduces the differentiation and expansion of Th17 cells in young asthmatic children

Vitamin D [25(OH)D3] deficiency has been associated with asthma as in many inflammatory and autoimmune pathologies; however, there is still a lack of data about the effects of administration of vitamin D in immune regulation in young asthmatic patients. In this study, we investigated its inhibitory effect on the immune response in young asthmatic patients and the possible mechanisms involved. Peripheral blood CD4(+) T cells from 10 asthmatic patients and 10 healthy controls were cultured under Th17 polarizing conditions in the presence or absence of [25(OH)D3], IL-17 cytokine production was determined by ELISA and flow cytometry. Messenger RNA (mRNA) expression of several factors related to Th17 cell function was determined by real-time PCR. The effect of [25(OH)D3]-treated dendritic cells (DCs) on CD4(+) T cell response was determined by ELISA and flow cytometry. Stimulation of naive CD4(+) T cells under Th17 polarizing conditions showed a higher Th17 cell differentiation in asthmatic patients than healthy controls. The addition of [25(OH)D3] significantly inhibited Th17 cell differentiation both in patients [P<0.001] and in normal controls [P=0.001] in a dose-dependent way. [25(OH)D3] was able to inhibit the gene expression of RORC, IL-17, IL-23R, and CCR6. [25(OH)D3]-treated DCs significantly inhibited IL-17 production [P=0.002] and decreased the percentage of CD4(+)IL-17(+) [P=0.007] in young asthmatics. The findings suggest that the inhibitory effect of [25(OH)D3] on the Th17 response was mediated via both T cells and DCs. DCs pathway is involved in the direct inhibition of 25(OH)D3 on Th17 cell differentiation in young asthmatics.

IL-27 limits central nervous system viral clearance by promoting IL-10 and enhances demyelination

IL-27 is a pleiotropic member of the IL-6 and IL-12 cytokine family composed of the IL-27p28 and the EBV-induced gene 3. IL-27 and its receptor mRNA are both upregulated in the CNS during acute encephalomyelitis induced by the JHM strain of mouse hepatitis virus (JHMV) and sustained during viral persistence. Contributions of IL-27 to viral pathogenesis were evaluated by infection of IL-27Rα-chain-deficient (IL-27Rα(-/-)) mice. The absence of IL-27 signaling accelerated virus control within the CNS associated with increased IFN-γ secreting virus-specific CD4+ and CD8+ T cells. Abrogation of IL-27 signaling did not affect virus-specific CD8+ T cell-mediated IL-10 production or cytolytic activity or Foxp3+ regulatory T cell populations. However, IL-10 production by virus-specific CD4+ T cells was reduced significantly. Despite increased T cell-mediated antiviral function in IL-27Rα(-/-) mice, the virus persisted in the CNS at similar levels as in wild-type mice. Nevertheless, IL-27Rα(-/-) mice exhibited decreased clinical disease during persistence, coincident with less severe demyelination, the hallmark tissue damage associated with JHMV infection. Overall, these data demonstrate that in contrast to viral infections at other sites, IL-27 does not play a proinflammatory role during JHMV-induced encephalomyelitis. Rather, it limits CNS inflammation and impairs control of CNS virus replication via induction of IL-10 in virus-specific CD4+ T cells. Furthermore, in contrast to its protective role in limiting CNS autoimmunity and preventing immunopathology, these data define a detrimental role of IL-27 in promoting demyelination by delaying viral control.

c-FLIP-Short reduces type I interferon production and increases viremia with coxsackievirus B3

Cellular FLIP (c-FLIP) is an enzymatically inactive paralogue of caspase-8 and as such can block death receptor-induced apoptosis. However, independent of death receptors, c-FLIP-Long (c-FLIP_L) can heterodimerize with and activate caspase-8. This is critical for promoting the growth and survival of T lymphocytes as well as the regulation of the RIG-I helicase pathway for type I interferon production in response to viral infections. Truncated forms of FLIP also exist in mammalian cells (c-FLIP_S) and certain viruses (v-FLIP), which lack the C-terminal domain that activates caspase-8. Thus, the ratio of c-FLIP_L to these short forms of FLIP may greatly influence the outcome of an immune response. We examined this model in mice transgenically expressing c-FLIP_S in T cells during infection with Coxsackievirus B3 (CVB3). In contrast to our earlier findings of reduced myocarditis and mortality with CVB3 infection of c-FLIP_L-transgenic mice, c-FLIP_S-transgenic mice were highly sensitive to CVB3 infection as manifested by increased cardiac virus titers, myocarditis score, and mortality compared to wild-type C57BL/6 mice. This observation was paralleled by a reduction in serum levels of IL-10 and IFN-α in CVB3-infected c-FLIP_S mice. In vitro infection of c-FLIP_S T cells with CVB3 confirmed these results. Furthermore, molecular studies revealed that following infection of cells with CVB3, c-FLIP_L associates with mitochondrial antiviral signaling protein (MAVS), increases caspase-8 activity and type I IFN production, and reduces viral replication, whereas c-FLIP_S promotes the opposite phenotype.

Catechin ameliorates cardiac dysfunction in rats with chronic heart failure by regulating the balance between Th17 and Treg cells

OBJECTIVE

Disequilibrium of the cytokine network was reported to play an important role in the progression of chronic heart failure (CHF). Catechin exerts cardioprotection through treating many kinds of angiocardiopathy. However, the effects of catechin on CHF are currently unclear. Therefore, the main aim of this study was to investigate the efficacy of catechin on CHF rats as well as its relationship to immunoregulation.

METHODS

CHF was induced in rats by ligation of the abdominal aorta. Myocardial function was evaluated by left ventricular systolic pressure and left ventricular end-diastolic pressure. The cytokine level was measured by enzyme-linked immunosorbent assay. Th17 and Treg levels in peripheral blood and spleen were analyzed by flow cytometry.

RESULTS

The results showed that catechin treatment (50, 100 mg/kg/day) markedly improved myocardial function in rats treated with abdominal aortic coarctation. Severity of myocardial dysfunction in CHF rats significantly correlated with serum values of interleukin-17 (IL-17)/IL-10. Further results indicated catechin obviously inhibited immune activation, regulated unbalanced levels of IL-17/IL-10, and reversed abnormal polarization of TH17 as well as Treg in peripheral blood and spleen.

CONCLUSIONS

Taken together, oral administration of catechin effectively suppressed abdominal aorta ligation-induced CHF in rats, which was closely associated with its modulation on Th17 and Treg.

CD4CD8αα lymphocytes, a novel human regulatory T cell subset induced by colonic bacteria and deficient in patients with inflammatory bowel disease

Gut bacterium Faecalibacterium prausnitzii activates a newly identified set of human IL-10-producing Treg cells (CD4CD8αα lymphocytes), revealing a mechanism by which commensal microbes contribute to host immunity.

How the microbiota affects health and disease is a crucial question. In mice, gut Clostridium bacteria are potent inducers of colonic interleukin (IL)-10-producing Foxp3 regulatory T cells (Treg), which play key roles in the prevention of colitis and in systemic immunity. In humans, although gut microbiota dysbiosis is associated with immune disorders, the underlying mechanism remains unknown. In contrast with mice, the contribution of Foxp3 Treg in colitis prevention has been questioned, suggesting that other compensatory regulatory cells or mechanisms may exist. Here we addressed the regulatory role of the CD4CD8 T cells whose presence had been reported in the intestinal mucosa and blood. Using colonic lamina propria lymphocytes (LPL) and peripheral blood lymphocytes (PBL) from healthy individuals, and those with colon cancer and irritable bowel disease (IBD), we demonstrated that CD4CD8αα (DP8α) T lymphocytes expressed most of the regulatory markers and functions of Foxp3 Treg and secreted IL-10. Strikingly, DP8α LPL and PBL exhibited a highly skewed repertoire toward the recognition of Faecalibacterium prausnitzii, a major Clostridium species of the human gut microbiota, which is decreased in patients with IBD. Furthermore, the frequencies of DP8α PBL and colonic LPL were lower in patients with IBD than in healthy donors and in the healthy mucosa of patients with colon cancer, respectively. Moreover, PBL and LPL from most patients with active IBD failed to respond to F. prausnitzii in contrast to PBL and LPL from patients in remission and/or healthy donors. These data (i) uncover a Clostridium-specific IL-10-secreting Treg subset present in the human colonic LP and blood, (ii) identify F. prausnitzii as a major inducer of these Treg, (iii) argue that these cells contribute to the control or prevention of colitis, opening new diagnostic and therapeutic strategies for IBD, and (iv) provide new tools to address the systemic impact of both these Treg and the intestinal microbiota on the human immune homeostasis.

It has become evident that bacteria in our gut affect health and disease, but less is known about how they do this. Recent studies in mice showed that gut Clostridium bacteria and their metabolites can activate regulatory T cells (Treg) that in turn mediate tolerance to signals that would ordinarily cause inflammation. In this study we identify a subset of human T lymphocytes, designated CD4CD8αα T cells that are present in the surface lining of the colon and in the blood. We demonstrate Treg activity and show these cells to be activated by microbiota; we identify F. prausnitzii, a core Clostridium strain of the human gut microbiota, as a major inducer of these Treg cells. Interestingly, there are fewer F. prausnitzii in individuals suffering from inflammatory bowel disease (IBD), and accordingly the CD4CD8αα T cells are decreased in the blood and gut of patients with IBD. We argue that CD4CD8αα colonic Treg probably help control or prevent IBD. These data open the road to new diagnostic and therapeutic strategies for the management of IBD and provide new tools to address the impact of the intestinal microbiota on the human immune system.

5-azacytidine promotes an inhibitory T-cell phenotype and impairs immune mediated antileukemic activity

Demethylating agent, 5-Azacytidine (5-Aza), has been shown to be active in treatment of myeloid malignancies. 5-Aza enhances anticancer immunity, by increasing expression of tumor-associated antigens. However, the impact of 5-Aza immune responses remains poorly understood. Here, T-cell mediated tumor immunity effects of 5-Aza, are investigated in vitro and in vivo. T-cells from healthy donors were treated with 5-Aza and analyzed by qRT-PCR and flow cytometry for changes in gene expression and phenotype. Functionality was assessed by a tumor lysis assay. Peripheral blood from patients treated with 5-Aza after alloSCT was monitored for changes in T-cell subpopulations. 5-Aza treatment resulted in a decrease in CD8+ T-cells, whereas CD4+ T-cells increased. Furthermore, numbers of IFN-γ+ T-helper 1 cells (Th1) were reduced, while Treg-cells showed substantial increase. Additionally, CD8+ T-cells exhibited limited killing capacity against leukemic target cells. In vivo data confirm the increase of Treg compartment, while CD8+ T-effector cell numbers were reduced. 5-Aza treatment results in a shift from cytotoxic to regulatory T-cells with a functional phenotype and a major reduction in proinflammatory Th1-cells, indicating a strong inhibition of tumor-specific T-cell immunity by 5-Aza.

Highly prevalent colorectal cancer-infiltrating LAP⁺ Foxp3⁻ T cells exhibit more potent immunosuppressive activity than Foxp3⁺ regulatory T cells

Although elevated CD4⁺Foxp3⁺ regulatory T cell (Treg) frequencies within tumors are well documented, the functional and phenotypic characteristics of CD4⁺Foxp3⁺ and CD4⁺Foxp3⁻ T cell subsets from matched blood, healthy colon, and colorectal cancer require in-depth investigation. Flow cytometry revealed that the majority of intratumoral CD4⁺Foxp3⁺ T cells (Tregs) were Helios⁺ and expressed higher levels of cytotoxic T-lymphocyte antigen 4 (CTLA-4) and CD39 than Tregs from colon and blood. Moreover, ∼30% of intratumoral CD4⁺Foxp3⁻ T cells expressed markers associated with regulatory functions, including latency-associated peptide (LAP), lymphocyte activation gene-3 (LAG-3), and CD25. This unique population of cells produced interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), and was ∼50-fold more suppressive than Foxp3⁺ Tregs. Thus, intratumoral Tregs are diverse, posing multiple obstacles to immunotherapeutic intervention in colorectal malignancies.

Mixed lymphocyte reaction induced by multiple alloantigens and the role for IL-10 in proliferation inhibition

The frequency of T cells that can respond to alloantigens is unusually high. It remains unclear how T cells would respond when stimulated by multiple major histocompatibility complex (MHC) disparate alloantigens in the same cultures. In this report, we examined potential interactions of T cell clones that were stimulated simultaneously by two sets of complete MHC disparate alloantigens using mixed lymphocyte reaction (MLR). In this assay, we observed that proliferation of B6 lymphocytes (H-2b) stimulated by both BALB/c (H-2d) and C3H (H-2k) allogeneic cells was not increased but rather reduced as compared to B6 cells stimulated with either BALB/c or C3H allogeneic cells. Interestingly, interleukin (IL)-10 expressions at both protein level and mRNA level was significantly increased in cultures stimulated with the two MHC alloantigens, while IL-2, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1 production did not show any differences. In addition, Foxp3 mRNA expression was comparable amongst all groups. In conclusion, we observed an inhibitory effect in T cell proliferation in response to multiple MHC mismatched alloantigens in MLR, and this effect might be associated with the upregulation of IL-10 expression.

Th17 and regulatory T cell balance in autoimmune and inflammatory diseases

This review focuses on the biology of T helper 17 (Th17) and regulatory T (Treg) cells and their role in inflammatory diseases, such as rheumatoid arthritis. Th17 cells represent a pro-inflammatory subset whereas Treg cells have an antagonist effect. Their developmental pathways are reciprocally interconnected and there is an important plasticity between Th17 and Treg cells. These features implicate that the Th17/Treg balance plays a major role in the development and the disease outcomes of animal model and human autoimmune/inflammatory diseases. During these diseases, this balance is disturbed and this promotes the maintenance of inflammation. Targeting the Th17/Treg imbalance can be performed at different levels such as inhibition of pro-inflammatory cytokines and their receptors, of pathogenic cells or their specific signaling pathways. Conversely, direct effects include administration or induction of protective cells, or stimulation of their specific pathways. Several clinical trials are underway and some positive results have been obtained.

Enhanced response to pulmonary Streptococcus pneumoniae infection is associated with primary ciliary dyskinesia in mice lacking Pcdp1 and Spef2

Background

Lower airway abnormalities are common in patients with primary ciliary dyskinesia (PCD), a pediatric syndrome that results from structural or functional defects in motile cilia. Patients can suffer from recurrent bacterial infection in the lung, bronchiectasis, and respiratory distress in addition to chronic sinusitis, otitis media, infertility, and laterality defects. However, surprisingly little is known about the pulmonary phenotype of mouse models of this disorder.

Results

The pulmonary phenotype of two mouse models of PCD, nm1054 and bgh, which lack Pcdp1 and Spef2, respectively, was investigated by histological and immunohistochemical analysis. In addition, both models were challenged with Streptococcus pneumoniae, a common respiratory pathogen found in the lungs of PCD patients. Histopathological analyses reveal no detectable cellular, developmental, or inflammatory abnormalities in the lower airway of either PCD model. However, exposure to S. pneumoniae results in a markedly enhanced inflammatory response in both models. Based on analysis of inflammatory cells in bronchoalveolar lavage fluid and flow cytometric analysis of cytokines in the lung, the bgh model shows a particularly dramatic lymphocytic response by 3 days post-infection compared to the nm1054 model or wild type animals.

Conclusions

Defects in ciliary motility result in a severe response to pulmonary infection. The PCD models nm1054 and bgh are distinct and clinically relevant models for future studies investigating the role of mucociliary clearance in host defense.

The resolution of neuroinflammation in neurodegeneration: leukocyte recruitment via the choroid plexus

Inflammation is an integral part of the body's physiological repair mechanism, unless it remains unresolved and becomes pathological, as evident in the progressive nature of neurodegeneration. Based on studies from outside the central nervous system (CNS), it is now understood that the resolution of inflammation is an active process, which is dependent on well-orchestrated innate and adaptive immune responses. Due to the immunologically privileged status of the CNS, such resolution mechanism has been mostly ignored. Here, we discuss resolution of neuroinflammation as a process that depends on a network of immune cells operating in a tightly regulated sequence, involving the brain's choroid plexus (CP), a unique neuro-immunological interface, positioned to integrate signals it receives from the CNS parenchyma with signals coming from circulating immune cells, and to function as an on-alert gate for selective recruitment of inflammation-resolving leukocytes to the inflamed CNS parenchyma. Finally, we propose that functional dysregulation of the CP reflects a common underlying mechanism in the pathophysiology of neurodegenerative diseases, and can thus serve as a potential novel target for therapy.

Clinical validation of IFNγ/IL-10 and IFNγ/IL-2 FluoroSpot assays for the detection of Tr1 T cells and influenza vaccine monitoring in humans

The type of T cell polarization and simultaneous production of multiple cytokines have been correlated with vaccine efficacy. ELISpot is a T cell detection technique optimized for the measurement of a secreted cytokine at the single cell level. The FluoroSpot assay differs from ELISpot by the use of multiple fluorescent-labeled anticytokine detection antibodies, allowing optimal measurement of multiple cytokines. In the present study, we show that an IFNγ/IL-10 FluoroSpot assay is more sensitive than flow cytometry to detect Tr1 regulatory T cells, an immunosuppressive T cell population characterized by the production of IL-10 and IFNγ. As many tolerogenic vaccines are designed to induce these Tr1 cells, this FluoroSpot test could represent a standard method for the detection of these cells in the future. The use of an IFNγ/IL-2 FluoroSpot assay during influenza vaccine monitoring showed that the influenza-specific IL-2-producing T-cell response was the dominant response both before and after vaccine administration. This study therefore questions the rationale of using the single-color IFNγ ELISpot as the standard technique to monitor vaccine-specific T-cell response. Using this same test, a trend was also observed between baseline levels of IFNγ T cell response and T cell vaccine response. In addition, a lower IFNγ+IL-2+ T-cell response after vaccine was observed in the group of patients treated with TNFα inhibitors (P=0.08). This study therefore supports the use of the FluoroSpot assay due to its robustness, versatility and the complementary information that it provides compared with ELISpot or flow cytometry to monitor vaccine-specific T-cell responses.

Importance of regulatory T cells in the pathogenesis of psoriasis: review of the literature

Psoriasis is a common chronic relapsing inflammatory cutaneous disease; the main role in the inflammation of this condition is played by lymphocyte Th1, Th17 and their cytokines. The activity of these cells is modulated by a particular kind of T cells recently described: the T regulatory cells (Treg). These are able to inhibit the immunological response and to maintain the cutaneous immunological homeostasis, thus preventing autoimmunity against self antigens. Few data are available in the literature as to Treg in psoriasis; several studies demonstrate that the function of these cells is impaired in this condition and treatments for psoriasis may increase the number and activity of Treg. The role of these cells in the pathogenesis of psoriasis is very important to understand how they may contribute to the development of this cutaneous disorder. In the near future it would be possible to target therapies at these defects, improving the activity of these cells and maintaining cutaneous homeostasis, preventing psoriasis or other inflammatory cutaneous conditions.

Food allergy: management, diagnosis and treatment strategies

Food allergy is an increasing problem in western countries, with strict avoidance being the only available reliable treatment. However, accidental ingestion can occur and anaphylactic reactions still happen. In recent years, many efforts have been made to better understand the humoral and cellular mechanisms involved in food allergy, and to improve the strategies for diagnosis and treatment. This review focuses on IgE-mediated food hypersensitivity and provides an overview of the diagnostic strategies and treatment advances. Specific immunotherapy, including different routes of administration and allergen sources, such as natural, recombinant and T-cell epitopes, are analyzed in detail. Other treatments such as anti-IgE monoclonal antibody therapy, adjuvant therapy and Chinese herbs will also be described.

Blocking of p38 and transforming growth factor β receptor pathways impairs the ability of tolerogenic dendritic cells to suppress murine arthritis

OBJECTIVE

Dendritic cells (DCs) modulated with lipopolysaccharide (LPS) are able to reduce inflammation when therapeutically administered into mice with collagen-induced arthritis (CIA). The aim of this study was to uncover the mechanisms that define the tolerogenic effect of short-term LPS-modulated DCs on CIA.

METHODS

Bone marrow-derived DCs were stimulated for 4 hours with LPS and characterized for their expression of maturation markers and their cytokine secretion profiles. Stimulated cells were treated with SB203580 or SB431542 to inhibit the p38 or transforming growth factor β (TGFβ) receptor pathway, respectively, or were left unmodified and, on day 35 after CIA induction, were used to inoculate mice. Disease severity was evaluated clinically. CD4+ T cell populations were counted in the spleen and lymph nodes from inoculated or untreated mice with CIA. CD4+ splenic T cells were transferred from mice with CIA treated with LPS-stimulated DCs or from untreated mice with CIA into other mice with CIA on day 35 of arthritis.

RESULTS

Treatment with LPS-stimulated DCs increased the numbers of interleukin-10 (IL-10)-secreting and TGFβ-secreting CD4+ T cells, but decreased the numbers of Th17 cells. Adoptive transfer of CD4+ T cells from treated mice with CIA reproduced the inhibition of active CIA accomplished with LPS-stimulated DCs. The therapeutic effect of LPS-stimulated DCs and their influence on T cell populations were abolished when the p38 and the TGFβ receptor pathways were inhibited.

CONCLUSION

DCs modulated short-term (4 hours) with LPS are able to confer a sustained cure in mice with established arthritis by re-educating the CD4+ T cell populations. This effect is dependent on the p38 and the TGFβ receptor signaling pathways, which suggests the participation of IL-10 and TGFβ in the recovery of tolerance.

CD8+ T cell exhaustion during persistent viral infection is regulated independently of the virus-specific T cell receptor

During chronic viral infections, responses by virus-specific CD8(+) T cells become marginalized by the acquisition of functional defects and reduced cell numbers in a process defined as T cell exhaustion. Similarly, T cell tolerance to self-antigen is also characterized by impaired effector function and eventual deletion of self-reactive T cells. Induction of both tolerance and exhaustion involve many shared inhibitory mechanisms, thus similar therapeutic approaches have proven effective in these distinct environments. We previously demonstrated that tolerant self-reactive CD8(+) T cells expressing dual-T cell receptors (i.e., dual-TCR) could be rescued by immunization through a second TCR specific for a foreign antigen. These data revealed that T cell tolerance was regulated at the level of the self-reactive TCR. Here, dual-TCR CD8(+) T cells were used to examine if exhaustion during persistent viral infection could be rescued by an analogous strategy of immunization through a second TCR not involved in recognition of virus. In direct contrast to the rescue achievable in tolerant CD8(+) T cells, exhausted T cells were equally impaired through both TCR. These findings suggest that exhaustion is maintained by defects downstream of the virus-specific TCR, and establish that exhaustion and tolerance are distinctly regulated states of T cell dysfunction.

Treating depression and depression-like behavior with physical activity: an immune perspective

The increasing burden of major depressive disorder makes the search for an extended understanding of etiology, and for the development of additional treatments highly significant. Biological factors may be useful biomarkers for treatment with physical activity (PA), and neurobiological effects of PA may herald new therapeutic development in the future. This paper provides a thorough and up-to-date review of studies examining the neuroimmunomodulatory effects of PA on the brain in depression and depression-like behaviors. From a neuroimmune perspective, evidence suggests PA does enhance the beneficial and reduce the detrimental effects of the neuroimmune system. PA appears to increase the following factors: interleukin (IL)-10, IL-6 (acutely), macrophage migration inhibitory factor, central nervous system-specific autoreactive CD4+ T cells, M2 microglia, quiescent astrocytes, CX3CL1, and insulin-like growth factor-1. On the other hand, PA appears to reduce detrimental neuroimmune factors such as: Th1/Th2 balance, pro-inflammatory cytokines, C-reactive protein, M1 microglia, and reactive astrocytes. The effect of other mechanisms is unknown, such as: CD4+CD25+ T regulatory cells (T regs), CD200, chemokines, miRNA, M2-type blood-derived macrophages, and tumor necrosis factor (TNF)-α [via receptor 2 (R2)]. The beneficial effects of PA are likely to occur centrally and peripherally (e.g., in visceral fat reduction). The investigation of the neuroimmune effects of PA on depression and depression-like behavior is a rapidly developing and important field.

Ribavirin modulates the conversion of human CD4(+) CD25(-) T cell to CD4(+) CD25(+) FOXP3(+) T cell via suppressing interleukin-10-producing regulatory T cell

Because regulatory T (Treg) cells play an important role in modulating the immune system response against both endogenous and exogenous antigens, their control is critical to establish immunotherapy against autoimmune disorders, chronic viral infections and tumours. Ribavirin (RBV), an antiviral reagent used with interferon, is known to polarize the T helper (Th) 1/2 cell balance toward Th1 cells. Although the immunoregulatory mechanisms of RBV are not fully understood, it has been expected that RBV would affect T reg cells to modulate the Th1/2 cell balance. To confirm this hypothesis, we investigated whether RBV modulates the inhibitory activity of human peripheral CD4(+)  CD25(+)  CD127(-) T cells in vitro. CD4(+)  CD25(+)  CD127(-) T cells pre-incubated with RBV lose their ability to inhibit the proliferation of CD4(+)  CD25(-) T cells. Expression of Forkhead box P3 (FOXP3) in CD4(+)  CD25(-) T cells was down-modulated when they were incubated with CD4(+)  CD25(+)  CD127(-) T cells pre-incubated with RBV without down-modulating CD45RO on their surface. In addition, transwell assays and cytokine-neutralizing assays revealed that this effect depended mainly on the inhibition of interleukin-10 (IL-10) produced from CD4(+)  CD25(+)  CD127(-) T cells. These results indicated that RBV might inhibit the conversion of CD4(+)  CD25(-)  FOXP3(-) naive T cells into CD4(+)  CD25(+)  FOXP3(+) adaptive Treg cells by down-modulating the IL-10-producing Treg 1 cells to prevent these effector T cells from entering anergy and to maintain Th1 cell activity. Taken together, our findings suggest that RBV would be useful for both elimination of long-term viral infections such as hepatitis C virus infection and for up-regulation of tumour-specific cellular immune responses to prevent carcinogenesis, especially hepatocellular carcinoma.

Pretreatment with glycomacropeptide reduces allergen sensitization, alleviates immediate cutaneous hypersensitivity and protects from anaphylaxis

Allergic disorders are characterized by the involvement of allergen-specific immunoglobulin (Ig)E antibodies and T helper type 2 (Th2) cells. The search for new therapies for allergic diseases has been the primary focus of interest for many investigators in recent years. Glycomacropeptide (GMP) is a biologically active component of milk that exhibits a range of immunomodulatory functions. We examined whether oral administration of GMP could affect the development of allergic sensitization and the severity of immediate cutaneous hypersensitivity reactions and of anaphylaxis. Rats treated with or without GMP were ovalbumin (OVA)-sensitized and several indicators of allergy were evaluated. Pretreatment with GMP resulted in reduction of antigen-specific IgE titre in rats when sensitized with OVA. GMP administration also markedly suppressed the proliferative response of splenocytes to antigen and the production of interleukin (IL)-13 by splenocytes of sensitized animals. In addition, GMP pretreatment attenuated the intensity of the immediate cutaneous reaction induced by antigen and protected the sensitized rats from severe anaphylaxis. These data demonstrate, for the first time, that the administration of GMP prevents allergen sensitization and reduces the severity of the early-phase reaction induced by antigen in cutaneous hypersensitivity and in anaphylaxis. GMP may be used as a novel prophylactic agent for the control of allergic diseases.

β-glucan curdlan induces IL-10-producing CD4+ T cells and inhibits allergic airway inflammation

A number of studies have suggested a correlation between a decreased incidence in infectious diseases and an increased incidence of allergic diseases, including asthma. Although several pathogen-derived products have been shown to possess therapeutic potential for allergic diseases, it remains largely unknown whether β-glucan, a cell wall component of a variety of fungi, yeasts, and bacteria, has a regulatory potential for allergic diseases. In this study, we examined the effect of curdlan, a linear β-(1-3)-glucan, on the development of allergic airway inflammation. We found that i.p. injection of curdlan significantly inhibited Ag-induced eosinophil recruitment and Th2 cytokine production in the airways. The activation of CD4(+) T cells in the presence of curdlan induced IL-10-producing CD4(+) T cells with high levels of c-Maf expression. Curdlan-induced development of IL-10-producing CD4(+) T cells required the presence of APCs and ICOS/ICOS ligand interaction. Curdlan-induced development of IL-10-producing CD4(+) T cells also required intrinsic expression of STAT6. Furthermore, the transfer of Ag-specific CD4(+) T cells that were stimulated in the presence of curdlan inhibited Ag-induced eosinophil recruitment into the airways. Taken together, these results suggest that curdlan is capable of inducing IL-10-producing CD4(+) T cells and inhibiting the development of eosinohilic airway inflammation, underscoring the therapeutic potential of curdlan for allergic diseases.

Temporal and spatial interplay of microbiota and intestinal mucosa drive establishment of immune homeostasis in conventionalized mice

During colonization of germfree mice with the total fecal microbial community of their conventionally born and raised siblings (conventionalization), the intestinal mucosal immune system initiates and maintains a balanced immune response. However, the genetic regulation of these balanced, appropriate responses to the microbiota is obscure. Here, combined analysis of germfree and conventionalized mice revealed that the major molecular responses could be detected initiating at day 4 post conventionalization, with a strong induction of innate immune functions followed by stimulation of adaptive immune responses and development and expansion of adaptive immune cells at later stages of conventionalization. This study provides a comprehensive overview of mouse developmental and immune-related cellular pathways and processes that were co-mediated by the commensal microbiota and suggests which mechanisms were involved in this reprogramming. The dynamic, region-dependent mucosal responses to the colonizing microbiota revealed potential transcriptional signatures for the control of intestinal homeostasis in healthy mice, which may help to decipher the genetic basis of pathway dysregulation in human intestinal inflammatory diseases.

Partial regulatory T cell depletion prior to schistosomiasis vaccination does not enhance the protection

CD4⁺CD25⁺ regulatory T cells (Tregs) do not only influence self-antigen specific immune responses, but also dampen the protective effect induced by a number of vaccines. The impact of CD4⁺CD25⁺ Tregs on vaccines against schistosomiasis, a neglected tropical disease that is a major public health concern, however, has not been examined. In this study, a DNA vaccine encoding a 26 kDa glutathione S-transferase of Schistosoma japonicum (pVAX1-Sj26GST) was constructed and its potential effects were evaluated by depleting CD25⁺ cells prior to pVAX1-Sj26GST immunization. This work shows that removal of CD25⁺ cells prior to immunization with the pVAX1-Sj26GST schistosomiasis DNA vaccine significantly increases the proliferation of splenocytes and IgG levels. However, CD25⁺ cell-depleted mice immunized with pVAX1-Sj26GST show no improved protection against S. japonicum. Furthermore, depletion of CD25⁺ cells causes an increase in both pro-inflammatory cytokines (e.g. IFN-γ, GM-CSF and IL-4) and an anti-inflammatory cytokine (e.g. IL-10), with CD4⁺CD25^- T cells being one of the major sources of both IFN-γ and IL-10. These findings indicate that partial CD25⁺ cell depletion fails to enhance the effectiveness of the schistosome vaccine, possibly due to IL-10 production by CD4⁺CD25^- T cells, or other cell types, after CD25⁺ cell depletion during vaccination.

Effect of Pru p 3 on dendritic cell maturation and T-lymphocyte proliferation in peach allergic patients

BACKGROUND

Pru p 3 is the major peach allergen and the most frequent cause of food allergy in adults in the Mediterranean area. Although its allergenicity is well characterized, its ability to generate a T-cell response is not completely known.

OBJECTIVE

To investigate the influence of Pru p 3 allergen on dendritic cell (DC) maturation and specific T-cell response (T(H)1/T(H)2) in peach allergic patients.

METHODS

Peach allergic patients (n = 11) and tolerant controls (n = 14) were included in the study. Monocyte-derived DC maturation after incubation with Pru p 3 was evaluated by the increase of maturational markers (CD80, CD86, and CD83) by flow cytometry. Lymphocyte proliferation was evaluated by coculturing monocyte-derived DCs and 5,6-carboxyfluorescein diacetate N-succinimidyl ester-stained lymphocytes with different concentrations of Pru p 3 (25, 10, and 1 μg/mL) by flow cytometry and cytokine production.

RESULTS

Pru p 3 induced a significant increase in the CD80, CD86, and CD83 expression on stimulated DCs from patients compared with controls. The lymphocyte proliferative response after Pru p 3 stimulation was also significantly higher along with an increase in interleukin 8 in patients compared with tolerant controls.

CONCLUSION

Pru p 3 allergen induces changes in DC maturational status mainly in peach allergic patients. An increase in lymphocyte proliferative response accompanied with a different cytokine pattern was also observed compared with healthy controls.

Regulatory T cell properties of thymic CD4+CD25+ cells in ducks

Thymic CD4(+)CD25(+) cells from ducks were characterized for mammalian T regulatory cells' suppressive and cytokine production properties. The cross reactivity of anti-chicken CD25 monoclonal antibody with duck CD25 was confirmed by evaluating Concanavalin-A-stimulated CD25 upregulation in splenocytes. CD4(+)CD25(+) cells were detectable in the thymus, spleen, cecal tonsil, and lung (airsacs), but not in the bursa. Duck CD4(+)CD25(+) cells had approximately nine-fold higher IL-10 mRNA, 12-fold higher TGF-β, 16-fold higher CTLA-4, and nine-fold higher LAG-3 mRNA amounts than thymic CD4(+)CD25(-) cells. Thymic CD4(+)CD25(+) cells had no detectable levels of IL-2 mRNA. Duck CD4(+)CD25(+) cells had a three-fold higher IL-10 mRNA amount than chicken CD4(+)CD25(+) cells. Duck CD4(+)CD25(+) cells were anergic in vitro. Duck CD4(+)CD25(+) cells suppressed naive cell proliferation at effector: responder cell ratios above 0.5:1 in both contact-dependent and -independent pathways. It could be concluded that thymic CD4(+)CD25(+) cells in ducks are most likely the counterpart of mammalian T regulatory cells.

Kv1.3 deletion biases T cells toward an immunoregulatory phenotype and renders mice resistant to autoimmune encephalomyelitis

Increasing evidence suggests ion channels have critical functions in the differentiation and plasticity of T cells. Kv1.3, a voltage-gated K(+) channel, is a functional marker and a pharmacological target for activated effector memory T cells. Selective Kv1.3 blockers have been shown to inhibit proliferation and cytokine production by human and rat effector memory T cells. We used Kv1.3 knockout (KO) mice to investigate the mechanism by which Kv1.3 blockade affects CD4(+) T cell differentiation during an inflammatory immune-mediated disease. Kv1.3 KO animals displayed significantly lower incidence and severity of myelin oligodendrocyte glycoprotein (MOG) peptide-induced experimental autoimmune encephalomyelitis. Kv1.3 was the only K(V) channel expressed in MOG 35-55-specific CD4(+) T cell blasts, and no K(V) current was present in MOG-specific CD4(+) T cell-blasts from Kv1.3 KO mice. Fewer CD4(+) T cells migrated to the CNS in Kv1.3 KO mice following disease induction, and Ag-specific proliferation of CD4(+) T cells from these mice was impaired with a corresponding cell-cycle delay. Kv1.3 was required for optimal expression of IFN-γ and IL-17, whereas its absence led to increased IL-10 production. Dendritic cells from Kv1.3 KO mice fully activated wild-type CD4(+) T cells, indicating a T cell-intrinsic defect in Kv1.3 KO mice. The loss of Kv1.3 led to a suppressive phenotype, which may contribute to the mechanism by which deletion of Kv1.3 produces an immunotherapeutic effect. Skewing of CD4(+) T cell differentiation toward Ag-specific regulatory T cells by pharmacological blockade or genetic suppression of Kv1.3 might be beneficial for therapy of immune-mediated diseases such as multiple sclerosis.

T regulatory cells control susceptibility to invasive pneumococcal pneumonia in mice

Streptococcus pneumoniae is an important human pathogen responsible for a spectrum of diseases including pneumonia. Immunological and pro-inflammatory processes induced in the lung during pneumococcal infection are well documented, but little is known about the role played by immunoregulatory cells and cytokines in the control of such responses. We demonstrate considerable differences in the immunomodulatory cytokine transforming growth factor (TGF)-β between the pneumococcal pneumonia resistant BALB/c and susceptible CBA/Ca mouse strains. Immunohistochemistry and flow cytometry reveal higher levels of TGF-β protein in BALB/c lungs during pneumococcal pneumonia that correlates with a rapid rise in lung Foxp3⁺Helios⁺ T regulatory cells. These cells have protective functions during pneumococcal pneumonia, because blocking their induction with an inhibitor of TGF-β impairs BALB/c resistance to infection and aids bacterial dissemination from lungs. Conversely, adoptive transfer of T regulatory cells to CBA/Ca mice, prior to infection, prolongs survival and decreases bacterial dissemination from lungs to blood. Importantly, strong T regulatory cell responses also correlate with disease-resistance in outbred MF1 mice, confirming the importance of immunoregulatory cells in controlling protective responses to the pneumococcus. This study provides exciting new evidence for the importance of immunomodulation during pulmonary pneumococcal infection and suggests that TGF-β signalling is a potential target for immunotherapy or drug design.

Streptococcus pneumoniae is a major human bacterial pathogen that causes a wide range of diseases including pneumonia, meningitis, sepsis and ear infections. The bacterium is responsible for around 1.2 million deaths per year, mostly in high-risk groups such as children, the elderly and those with a weakened immune system. Infection with the pneumococcus can induce a wide-variety of immune responses and disease symptoms and it is not known why some people are more resistant to infection than others. Here, we identify an important role in natural resistance against pneumococcal pneumonia for a group of cells – known as T regulatory cells – that control the immune response to pneumococcal infection. In mice, strong T regulatory cell responses correlate with resistance to invasive pneumococcal pneumonia. Disease-resistance can be boosted by administering T regulatory cells to highly susceptible mice or inhibited by blocking the activity of these cells in resistant mice. These results advance our understanding of the host immunity differences that underpin resistance to pneumococcal pneumonia and offer hope that in the future we might boost resistance in susceptible individuals through modulation of their immune system.

CD4⁺T cells: differentiation and functions

CD4⁺T cells are crucial in achieving a regulated effective immune response to pathogens. Naive CD4⁺T cells are activated after interaction with antigen-MHC complex and differentiate into specific subtypes depending mainly on the cytokine milieu of the microenvironment. Besides the classical T-helper 1 and T-helper 2, other subsets have been identified, including T-helper 17, regulatory T cell, follicular helper T cell, and T-helper 9, each with a characteristic cytokine profile. For a particular phenotype to be differentiated, a set of cytokine signaling pathways coupled with activation of lineage-specific transcription factors and epigenetic modifications at appropriate genes are required. The effector functions of these cells are mediated by the cytokines secreted by the differentiated cells. This paper will focus on the cytokine-signaling and the network of transcription factors responsible for the differentiation of naive CD4⁺T cells.