Leptin favors Th17/Treg cell subsets imbalance associated with allergic asthma severity.

Background: Obesity has often been associated with severe allergic asthma (AA). Here, we analyzed the frequency of different circulating CD4+T-cell subsets from lean, overweight and obese AA patients. Methods: Mononuclear cells from peripheral blood were obtained from 60 AA patients and the frequency of different CD4+T-cell subsets and type 1 regulatory B cells (Br1) was determined by cytometry. The effect of obese-related leptin dose on cytokine production and Treg cell function in AA-derived CD4+ T cell cultures was evaluated by ELISA and 3H thymidine uptake, respectively. Leptin levels were quantified in the plasma by ELISA. According to the BMI, patients were stratified as lean, overweight and obese. Results: AA severity, mainly among obese patients, was associated with an expansion of hybrid Th2/Th17 and Th17-like cells rather than classic Th2-like cells. On the other hand, the frequencies of Th1-like, Br1 cells and regulatory CD4+ T-cell subsets were lower in patients with severe AA. While percentages of the hybrid Th2/Th17 phenotype and Th17-like cells positively correlated with leptin levels, the frequencies of regulatory CD4+ T-cell subsets and Br1 cells negatively correlated with this adipokine. Interestingly, the obesity-related leptin dose not only elevated Th2 and Th17 cytokine levels, but also directly reduced the Treg function in CD4+ T cell cultures from lean AA patients. Conclusion: In summary, our results indicated that obesity might increase AA severity by favoring the expansion of Th17-like and Th2/Th17 cells and decreasing regulatory CD4+T cell subsets, being adverse effects probably mediated by leptin overproduction.

Serum leptin levels correlate negatively with the capacity of vitamin D to modulate the in vitro cytokines production by CD4+ T cells in asthmatic patients.

Both obesity and low vitamin D levels have been associated with allergic asthma (AA) severity. In the present study, severity of AA was associated with obesity but to the in vitro IgE production. In those patients, higher levels of IL-5, IL-6 and IL-17 were quantified in CD4+ T-cell cultures as compared with patients with mild and moderate AA. In addition, the lowest IL-10 levels were detected in the cell cultures from patients with a worse prognosis. Interestingly, the occurrence of AA elevates the plasma levels of leptin, and this adipokine was positively correlated with the release of IL-5, IL-6 and IL-17, but inversely correlated with IL-10 production, by CD4+ T-cells from patients. In AA-derived CD4+ T-cell cultures, 1,25(OH)2D3 was less efficient at inhibiting IL-5, IL-6 and IL-17 production, and up regulating IL-10 release, as those from healthy subjects. Interestingly, the in vitro immunomodulatory effects of vitamin D were inversely correlated with serum leptin levels. In summary, our findings suggested that obesity, probably due to the overproduction of leptin, negatively impacts AA as it favors imbalance between Th2/Th17 and regulatory phenotypes. The deleterious effects of leptin may also be due to its ability to counter-regulate the immunosuppressive effects of vitamin D.

TLR-2 and TLR-4 agonists favor expansion of CD4+ T cell subsets implicated in the severity of neuromyelitis optica spectrum disorders.

BACKGROUND: High frequency of circulating Th17 cell subsets expressing TLR2, TLR4 and TLR9 was observed in Neuromyelitis optica spectrum disorder (NMOSD) patients, a severe humoral autoimmune disease of the central nervous system. Our objective was to evaluate the direct effects of different TLR ligands on CD4+ T-cells form those patients. METHODS: CD4+ T-cell cultures from NMOSD and healthy individuals were stimulated with different TLR ligands and the cell proliferation and cytokine profile was analyzed by [3H] TdR up take and ELISA/ cytometry, respectively. The plasma levels of CD14 were determined by ELISA. RESULTS: Here, Pam3C (TLR2) and LPS (TLR4) induced significant cell proliferation and IL-6, IL-17 and IL-21 production by CD4+ T-cells from NMOSD. Additionally, while both TLR ligands were more potent in favoring the expansion of TFH-like cells, Pam3C reduced the frequency of IL-10-secreting FoxP3+and FoxP3- CD4+ T-cells. With regard to disease severity, the levels of IL-6, IL-17 and IL-21 produced by CD4+ T-cells, as well as the frequency of TFH-like cells, in response to TLR2 and TLR4 agonists were positively correlated with neurological disabilities and the occurrence of new acute relapses during follow up. Finally, circulating levels of CD14, an indirect marker of microbial translocation, were positively correlated with IL-6, IL-17 and IL-21 release by Pam3C- and LPS-activated CD4+ T-cells. CONCLUSIONS: In summary, our data suggest that microbial antigens may affect NMOSD outcomes by favoring an imbalance between Th17 and TFH-like cells and regulatory T cell subsets.

The expansion of circulating IL-6 and IL-17-secreting follicular helper T cells is associated with neurological disabilities in neuromyelitis optica spectrum disorders.

Due to their function in assisting B cells, TFH cells may be involved in the production of pathogenic IgG in neuromyelitis optica spectrum disorder (NMOSD). In the present study, the proportion of IL-6+ and IL-17+ TFH cell subsets was higher in NMOSD patients than healthy individuals. The frequency of both TFH cell subsets were directly associated with disease activity. By contrast, NMOSD patients with a higher proportion of IL-10+ TFH cell subsets showed a lower neurological disabilities score. In summary, all findings suggest that expansion of peripheral IL-6+ and IL-17+ TFH cells may be involved in the severity of NMOSD.

Serotonin decreases the production of Th1/Th17 cytokines and elevates the frequency of regulatory CD4+ T-cell subsets in multiple sclerosis patients.

Excessive levels of proinflammatory cytokines in the CNS are associated with reduced serotonin (5-HT) synthesis, a neurotransmitter with diverse immune effects. In this study, we evaluated the ability of exogenous 5-HT to modulate the T-cell behavior of patients with MS, a demyelinating autoimmune disease mediated by Th1 and Th17 cytokines. Here, 5-HT attenuated, in vitro, T-cell proliferation and Th1 and Th17 cytokines production in cell cultures from MS patients. Additionally, 5-HT reduced IFN-γ and IL-17 release by CD8+ T cells. By contrast, 5-HT increased IL-10 production by CD4+ T cells from MS patients. A more accurate analysis of these IL-10-secreting CD4+ T cells revealed that 5-HT favors the expansion of FoxP3+ CD39+ regulatory T cells (Tregs) and type 1 regulatory T cells. Notably, this neurotransmitter also elevated the frequency of Treg17 cells, a novel regulatory T-cell subset. The effect of 5-HT in upregulating CD39+ Treg and Treg17 cells was inversely correlated with the number of active brain lesions. Finally, in addition to directly reducing cytokine production by purified Th1 and Th17 cells, 5-HT enhanced in vitro Treg function. In summary, our data suggest that serotonin may play a protective role in the pathogenesis of MS.

Expansion of IL-6+ Th17-like cells expressing TLRs correlates with microbial translocation and neurological disabilities in NMOSD patients.

Different microbial antigens, by signaling through toll-like receptors (TLR), may contribute to Th17-mediated autoimmune diseases, such as neuromyelitis optica spectrum disorder (NMOSD). The objective of this study was to determine the proportion of different Th17-like cell subsets that express TLR in NMOSD patients. For this study, the frequency of different Th17 cell subsets expressing TLR subsets in healthy individuals (n=20) and NMOSD patients (n=20) was evaluated by cytometry. The peripheral levels of soluble CD14 (sCD14) and cytokines were determined by ELISA. Our results demonstrated that the proportion of peripheral CD4+ T cells expressing TLR2, 4 and 9 was significantly higher in NMOSD samples than in healthy subjects. In NMOSD, these cells are CD28+PD-1-CD57- and produce elevated levels of IL-17. Among different TLRs+ Th17-like subsets, the proportion of those that co-express IL-17 and IL-6 was significantly higher in NMOSD patients, which was positively correlated with sCD14 levels and EDSS score. By contrast, the percentage of TLRs+Treg17 cells (IL-10+IL-17+) was negatively related to sCD14 and the severity of NMOSD. In conclusion, the expansion of peripheral IL-6-producing TLR+ Th17-like cells in NMOSD patients was associated with both bacterial translocation and disease severity.