Regulatory T-cell differentiation and their function in immune regulation

Gut Microbiota Structure and Metabolites, Before and After Treatment in Early Rheumatoid Arthritis Patients: A Pilot Study

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. Modifications of gut microbiota seem to be associated with the disease, but the impact of gut microbiota on therapies’ outcome remains unclear. A role of T cells in RA pathogenesis has been addressed, particularly on the Th17/Treg cells balance. Our study aimed to evaluate in early RA (ERA) patients compared to a control group, fecal gut microbiota composition, short-chain fatty acids concentrations, and the levels of circulating Th17/Treg and their own cytokines, before and after 3 months of standard treatment (Methotrexate (MTX) plus glucocorticoids). Fecal microbiota characterization was carried out on 19 ERA patients and 20 controls matched for sex and age. Significant decreased biodiversity levels, and a partition on the base of the microbiota composition, between the ERA patients at baseline compared to controls, were observed. The co-occurrent analysis of interactions revealed a characteristic clustered structure of the microbial network in controls that is lost in ERA patients where an altered connection between microbes and clinical parameters/metabolites has been reported. Microbial markers such as Acetanaerobacterium elongatum, Cristiansella massiliensis, and Gracilibacter thermotolerans resulted significantly enriched in control group while the species Blautia gnavus emerged to be more abundant in ERA patients. Our results showed an alteration in Th17/Treg balance with higher Th17 levels and lower Treg levels in ERA group respect to control at baseline, those data improved after therapy. Treatment administration and the achievement of a low disease activity/remission appear to exert a positive pressure on the structure of intestinal microbiota with the consequent restoration of biodiversity, of the structure of microbial network, and of the abundance of taxa that became closer to those presented by the subject without the disease. We also found an association between Blautia gnavus and ERA patients characterized by a significant reduction of propionic acid level. Furthermore significant differences highlighted at baseline among controls and ERA patients are no more evident after treatment. These data corroborate the role played by gut microbiota in the disease and suggest that therapy aimed to restore gut microbiota would improve treatment outcome.

High-frequency and activation of CD4+CD25+ T cells maintain persistent immunotolerance induced by congenital ALV-J infection

Congenital avian leukosis virus subgroup J (ALV-J) infection can induce persistent immunotolerance in chicken, however, the underlying mechanism remains unclear. Here, we demonstrate that congenital ALV-J infection induces the production of high-frequency and activated CD4⁺CD25⁺ Tregs that maintain persistent immunotolerance. A model of congenital infection by ALV-J was established in fertilized eggs, and hatched chicks showed persistent immunotolerance characterized by persistent viremia, immune organ dysplasia, severe imbalance of the ratio of CD4⁺/CD8⁺ T cells in blood and immune organs, and significant decrease in CD3⁺ T cells and Bu-1⁺ B cells in the spleen. Concurrently, the mRNA levels of IL-2, IL-10, and IFN-γ showed significant fluctuations in immune organs. Moreover, the frequency of CD4⁺CD25⁺ Tregs in blood and immune organs significantly increased, and the frequency of CD4⁺CD25⁺ Tregs was positively correlated with changes in ALV-J load in immune organs. Interestingly, CD4⁺CD25⁺ Tregs increased in the marginal zone of splenic nodules in ALV-J-infected chickens and dispersed to the germinal center. In addition, the proliferation and activation of B cells in splenic nodules was inhibited, and the number of IgM⁺ and IgG⁺ cells in the marginal zone significantly decreased. We further found that the mRNA levels of TGF- β and CTLA-4 in CD4⁺CD25⁺ Tregs of ALV-J-infected chickens significantly increased. Together, high-frequency and activated CD4⁺CD25⁺ Tregs inhibited B cells functions by expressing the inhibitory cytokine TGF-β and inhibitory surface receptor CTLA-4, thereby maintaining persistent immunotolerance in congenital ALV-J-infected chickens.

Chimeric antigen-guiding extracellular vesicles eliminate antigen-specific Th2 cells in subjects with food allergy

Background

Antigen (Ag)-specific T helper (Th)2 cells play a central role in food allergy (FA) pathogenesis. Methods can be used to eliminate Ag-specific Th2 cells that are currently lacking. This study aims to eliminate the Ag-specific Th2 cells with a novel nanoparticle, the mEV (modified extracellular vesicles, that carry a chimeric antigen peptide, MHC II and caspase 3) in a murine FA model.

Methods

mEVs were generated by exposing dendritic cells (DC) to ovalbumin (OVA, a specific Ag) and recombinant caspase 3 (Casp3) in the culture overnight. Exosomes were purified from culture supernatant by the magnetic antibody approach. A murine FA model was developed with OVA as the specific Ag.

Results

Purified mEVs had the molecular markers of extracellular vesicle, CD81, CD63, and CD9, cleaved Casp3 and MHC II/OVA complexes. mEVs specifically bound to the surface of Ag-specific CD4⁺ T cells, induced Ag-specific CD4⁺ T cell apoptosis both in vitro and in vivo as well as increased regulatory T cells in the intestinal tissues. Administration of mEV efficiently suppressed experimental FA.

Conclusions

mEVs carry Ag/MHC II complexes and Casp3, that can induce Ag-specific Th2 cell apoptosis. Administration of mEV can efficiently suppress experimental FA. The results suggest that the mEVs have the translational potential to be used in the treatment of FA and other allergic diseases.

Soluble CD83 suppresses experimental food allergy via regulating aberrant T helper 2 responses

Aberrant T helper-2 (Th2) responses play a critical role in the pathogenesis of allergic diseases. The underlying mechanism is to be further investigated. It is reported that soluble CD83 (sCD83) has immune-regulatory effects. This study aims to investigate the role of sCD83 in the regulation of Th2 polarization. Blood samples were collected from pediatric patients with food allergy (FA). The Th2 response was analyzed by pertinent immunological approaches. An FA murine model was developed to test the role of sCD83 in the regulation of FA response. We found that the serum sCD83 levels were lower in FA patients. A negative correlation was detected between serum sCD83 levels and serum Th2 cytokine levels. The presence of sCD83 suppressed Th2 cell differentiation and antigen-specific Th2 cell activation. sCD83 upregulated the T-bet expression and suppressed the GATA3 expression in CD4+ T cells. Administration of sCD83 suppressed experimental FA. Pediatric FA patients have low serum sCD83 levels. Administration of sCD83 can alleviate experimental FA via suppression of aberrant Th2 polarization.

Mal-deficiency impairs the tolerogenicity of dendritic cell of patients with allergic rhinitis

The tolerogenic dendritic cell dysfunction is associated with the pathogenesis of immune diseases. Microbial stimulus is required in the maintenance of immune functions. This study aims to elucidate the role of Mal signal in the maintenance of DEC205⁺ DC (decDC) immune tolerogenic function. In this study, peripheral DCs were collected from allergic rhinitis (AR) patients and healthy control (HC) subjects to assess the functional status of decDCs. An AR murine model was developed to test the role of Mal signals in the maintenance of decDCs' functions. We observed that AR decDCs (decDCs obtained from AR patients) were incompetent in the induction of type 1 regulatory T cells (Tr1 cells). AR decDCs expressed less IL-10 than that in HC decDCs. IL-10 mRNA decayed spontaneously in AR decDCs. Tat-activating regulatory DNA-binding protein-43 (TDP43) protected IL-10 mRNA from decay. AR decDCs expressed lower levels of Mal than that in HC decDCs. Mal depletion resulted in IL-10 mRNA decay in HC decDCs. Reconstitution of Mal in AR decDCs restored the capacity of inducing Tr1 cells and attenuated experimental AR in mice. In conclusion, Mal plays a critical role in the maintenance of decDC's immune tolerogenic function. The absence or insufficient Mal signal impairs decDC's tolerogenic property. Reconstitution of Mal in AR decDCs can restore the immune tolerogenic capacity, which may have translational potential in the treatment of AR and other allergic diseases.

Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata

The treatment of autoimmune diseases still poses a major challenge, frequently relying on non-specific immunosuppressive drugs. Current efforts aim at reestablishing self tolerance using immune cells with suppressive activity like the regulatory T cells (Treg) or the myeloid-derived suppressor cells (MDSC). We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA. Proteome analyses substantiated a large overlap of function-relevant molecules in MDSC and MDSC-Exo. Furthermore, MDSC-Exo are taken up by T cells, macrophages, NK, and most avidly by Treg and MDSC-Exo uptake exceeds binding of MDSC themselves. In AA mice, MDSC-Exo preferentially target skin-draining lymph nodes and cells in the vicinity of remnant hair follicles. MDSC-Exo uptake is accompanied by a strong increase in Treg, reduced T helper proliferation, mitigated cytotoxic activity, and a slight increase in lymphocyte apoptosis. Repeated MDSC-Exo application in florid AA prevented progression and sufficed for partial hair regrowth. Deep sequencing of lymphocyte mRNA from these mice revealed a significant increase in immunoregulatory mRNA, including FoxP3 and arginase 1. Downregulated mRNA was preferentially engaged in prohibiting T cell hyperreactivity. Taken together, proteome analysis provided important insights into potential MDSC-Exo activities, these Exo preferentially homing into AA-affected organs. Most importantly, changes in leukocyte mRNA seen after treatment of AA mice with MDSC-Exo sustainably supports the strong impact on the adaptive and the non-adaptive immune system, with Treg expansion being a dominant feature. Thus, MDSC-Exo could potentially serve as therapeutic agents in treating AA and other autoimmune diseases.

Increased CD4+CD45RA-FoxP3low cells alter the balance between Treg and Th17 cells in colitis mice

AIM

To investigate the role of regulatory T cell (Treg) subsets in the balance between Treg and T helper 17 (Th17) cells in various tissues from mice with dextran sulfate sodium-induced colitis.

METHODS

Treg cells, Treg cell subsets, Th17 cells, and CD4⁺CD25⁺FoxP3⁺IL-17⁺ cells from the lamina propria of colon (LPC) and other ulcerative colitis (UC) mouse tissues were evaluated by flow cytometry. Forkhead box protein 3 (FoxP3), interleukin 17A (IL-17A), and RORC mRNA levels were assessed by real-time PCR, while interleukin-10 (IL-10) and IL-17A levels were detected with a Cytometric Beads Array.

RESULTS

In peripheral blood monocytes (PBMC), mesenteric lymph node (MLN), lamina propria of jejunum (LPJ) and LPC from UC mice, Treg cell numbers were increased (P < 0.05), and FoxP3 and IL-10 mRNA levels were decreased. Th17 cell numbers were also increased in PBMC and LPC, as were IL-17A levels in PBMC, LPJ, and serum. The number of FrI subset cells (CD4⁺CD45RA⁺FoxP3^low) was increased in the spleen, MLN, LPJ, and LPC. FrII subset cells (CD4⁺CD45RA^-FoxP3^high) were decreased among PBMC, MLN, LPJ, and LPC, but the number of FrIII cells (CD4⁺CD45RA^-FoxP3^low) and CD4⁺CD25⁺FoxP3⁺IL-17A⁺ cells was increased. FoxP3 mRNA levels in CD4⁺CD45RA^-FoxP3^low cells decreased in PBMC, MLN, LPJ, and LPC in UC mice, while IL-17A and RORC mRNA increased. In UC mice the distribution of Treg, Th17 cells, CD4⁺CD45RA^-FoxP3^high, and CD4⁺CD45RA^-FoxP3^low cells was higher in LPC relative to other tissues.

CONCLUSION

Increased numbers of CD4⁺CD45RA^-FoxP3^low cells may cause an imbalance between Treg and Th17 cells that is mainly localized to the LPC rather than secondary lymphoid tissues.

Association of TLR4 and Treg in Helicobacter pylori Colonization and Inflammation in Mice

The host immune response plays an important role in the pathogenesis of Helicobacter pylori infection. The aim of this study was to clarify the immune pathogenic mechanism of Helicobacter pylori infection via TLR signaling and gastric mucosal Treg cells in mice. To discover the underlying mechanism, we selectively blocked the TLR signaling pathway and subpopulations of regulatory T cells in the gastric mucosa of mice, and examined the consequences on H. pylori infection and inflammatory response as measured by MyD88, NF-κB p65, and Foxp3 protein expression levels and the levels of Th1, Th17 and Th2 cytokines in the gastric mucosa. We determined that blocking TLR4 signaling in H. pylori infected mice decreased the numbers of Th1 and Th17 Treg cells compared to controls (P < 0.001-0.05), depressed the immune response as measured by inflammatory grade (P < 0.05), and enhanced H. pylori colonization (P < 0.05). In contrast, blocking CD25 had the opposite effects, wherein the Th1 and Th17 cell numbers were increased (P < 0.001-0.05), immune response was enhanced (P < 0.05), and H. pylori colonization was inhibited (P < 0.05) compared to the non-blocked group. In both blocked groups, the Th2 cytokine IL-4 remained unchanged, although IL-10 in the CD25 blocked group was significantly decreased (P < 0.05). Furthermore, MyD88, NF-κB p65, and Foxp3 in the non-blocked group were significantly lower than those in the TLR4 blocked group (P < 0.05), but significantly higher than those of the CD25 blocked group (P < 0.05). Together, these results suggest that there might be an interaction between TLR signaling and Treg cells that is important for limiting H. pylori colonization and suppressing the inflammatory response of infected mice.

The roles of IL-2 and IL-10 enhance anti-CD45RBmAb immune inhibition in allograft skin

As a new type of immune tolerance inducer, anti-CD45RB monoclonal antibodies (anti-CD45RBmAb) can prolong the graft survival time of animal organs or cell transplantation as well as induce stable immune tolerance. Both interleukin (IL)-2 and IL-10 have important roles in the induction and maintenance of immunological tolerance. However, whether these cytokines combined with anti-CD45RBmAb can promote immune tolerance is poorly understood. Therefore, we investigated the effect of IL-2 and IL-10 in vitro and in vivo on the tolerance induction by anti-CD45RBmAb. The changes of Treg and Th17 cells and Th1/Th2 cytokines in anti-CD45RBmAb induced prolongation of skin allograft survival in mice. The finding of a role for IL-2 is novel, of interest, IL-2 promoted anti-CD45RBmAb-induced CD4(+) T cell differentiation into Treg and Th2 cells and suppressed Th17 and Th1 cells. IL-2 enhanced the induction of immune tolerance by anti-CD45RBmAb and significantly prolonged skin graft survival time in vivo. In contrast, this effect should be demonstrated experimentally by neutralizing IL-2 and inhibition of the effect of anti-CD45RBmAb, and neutralizing IL-10 showed no effect for anti-CD45RBmAb-induced tolerance. These data reveal that IL-2 significantly enhances anti-CD45RBmAb-induced immune tolerance via up-regulated T regulatory (Treg) cells and the balance of Th1/Th2 shifts. Conversely, IL-10 showed no effect on anti-CD45RBmAb-induced tolerance.

Are Microglial Cells the Regulators of Lymphocyte Responses in the CNS?

The infiltration of immune cells in the central nervous system is a common hallmark in different neuroinflammatory conditions. Accumulating evidence indicates that resident glial cells can establish a cross-talk with infiltrated immune cells, including T-cells, regulating their recruitment, activation and function within the CNS. Although the healthy CNS has been thought to be devoid of professional dendritic cells (DCs), numerous studies have reported the presence of a population of DCs in specific locations such as the meninges, choroid plexuses and the perivascular space. Moreover, the infiltration of DC precursors during neuroinflammatory situations has been proposed, suggesting a putative role of these cells in the regulation of lymphocyte activity within the CNS. On the other hand, under specific circumstances, microglial cells are able to acquire a phenotype of DC expressing a wide range of molecules that equip these cells with all the necessary machinery for communication with T-cells. In this review, we summarize the current knowledge on the expression of molecules involved in the cross-talk with T-cells in both microglial cells and DCs and discuss the potential contribution of each of these cell populations on the control of lymphocyte function within the CNS.

Prognostic Significance of the Systemic Inflammatory and Immune Balance in Alcoholic Liver Disease with a Focus on Gender-Related Differences

Objectives

Mechanisms of immune regulation in alcoholic liver disease (ALD) are still unclear. The aim of our study was to determine an impact of Th17 / regulatory T (Treg) cells balance and its corresponding cytokine profile on the ALD outcome. Possible gender-related differences in the alcohol-induced inflammatory response were also assessed.

Materials and Methods

147 patients with ALD were prospectively recruited, assigned to subgroups based on their gender, severity of liver dysfunction and presence of ALD complications at admission, and followed for 90 days. Peripheral blood frequencies of Th17 and Treg cells together with IL-1beta, IL-6, IL-17A, IL-23, and TGF-beta1 levels were investigated. Flow cytometry was used to identify T cell phenotype and immunoenzymatic ELISAs for the corresponding cytokine concentrations assessment. Multivariable logistic regression was applied in order to select independent predictors of advanced liver dysfunction and the disease complications.

Results

IL-17A, IL-1beta, IL-6 levels were significantly increased, while TGF-beta1 decreased in ALD patients. The imbalance with significantly higher Th17 and lower Treg frequencies was observed in non-survivors. IL-6 and TGF-beta1 levels differed in relation to patient gender in ALD group. Concentrations of IL-6 were associated with the severity of liver dysfunction, development of ALD complications, and turned out to be the only independent immune predictor of 90-day survival in the study cohort.

Conclusions

We conclude that IL-6 revealed the highest diagnostic and prognostic potential among studied biomarkers and was related to the fatal ALD course. Gender-related differences in immune regulation might influence the susceptibility to alcohol-associated liver injury.

Altered immunoregulation in rheumatoid arthritis: the role of regulatory T cells and proinflammatory Th17 cells and therapeutic implications

In recent years several studies investigated the role of T lymphocyte subpopulations in the pathogenesis of rheumatoid arthritis (RA). Pathogenic Th17 cells mediate pannus growth, osteoclastogenesis, and synovial neoangiogenesis; hence they are key players in the development of the disease. On the other hand, regulatory T (Treg) cells are a T cell subset whose peculiar function is to suppress autoreactive lymphocytes. The imbalance between Th17 and Treg cells has been identified as a crucial event in the pathogenesis of RA. In addition, the effects of currently employed RA therapeutic strategies on these lymphocyte subpopulations have been extensively investigated. This review article aims to discuss current knowledge on Treg and Th17 cells in RA and possible implications of their therapeutic targeting in this disorder.