Fraction of IL-10+ and IL-17+ CD8 T cells is increased in MS patients in remission and during a relapse, but is not influenced by immune modulators

Role of autoreactive Tc17 cells in the pathogenesis of experimental autoimmune encephalomyelitis

Background

The pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE—an animal model of MS) is primarily mediated by T cells. However, recent studies have only focused on interleukin (IL)‐17‐secreting CD4+ T‐helper cells, also known as Th17 cells. This study aimed to compare Th17 cells and IL‐17‐secreting CD8+ T‐cytotoxic cells (Tc17) in the context of MS/EAE.

Methods

Female C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein peptides 35–55 (MOG35–55), pertussis toxin, and complete Freund's adjuvant to establish the EAE animal model. T cells were isolated from the spleen (12–14 days postimmunization). CD4+ and CD8+ T cells were purified using isolation kit and then differentiated into Th17 and Tc17, respectively, using MOG35–55 and IL‐23. The secretion levels of interferon‐γ (IFN‐γ) and IL‐17 were measured via enzyme‐linked immunosorbent assay using cultured CD4+ and CD8+ T cell supernatants. The pathogenicity of Tc17 and Th17 cells was assessed through adoptive transfer (tEAE), with the clinical course assessed using an EAE score (0–5). Hematoxylin and eosin as well as Luxol fast blue staining were used to examine the spinal cord. Purified CD8+ CD3+ and CD4+ CD3+ cells differentiated into Tc17 and Th17 cells, respectively, were stimulated with MOG35–55 peptide for proliferation assays.

Results

The results showed that Tc17 cells (15,951 ± 1985 vs. 55,709 ± 4196 cpm; p < 0.050) exhibited a weaker response to highest dose (20 μg/mL) MOG35–55 than Th17 cells. However, this response was not dependent on Th17 cells. After the 48 h stimulation, at the highest dose (20 μg/mL) of MOG35–55. Tc17 cells secreted lower levels of IFN‐γ (280.00 ± 15.00 vs. 556.67 ± 15.28 pg/mL, p < 0.050) and IL‐17 (102.67 ± 5.86 pg/mL vs. 288.33 ± 12.58 pg/mL; p < 0.050) than Th17 cells. Similar patterns were observed for IFN‐γ secretion at 96 and 144 h. Furthermore, Tc17 cell‐induced tEAE mice exhibited similar EAE scores to Th17 cell‐induced tEAE mice and also showed similar inflammation and demyelination.

Conclusion

The degree of pathogenicity of Tc17 cells in EAE is lower than that of Th17 cells. Future investigation on different immune cells and EAE models is warranted to determine the mechanisms underlying MS.

Alterations in CD4+ T Cell Cytokines Profile in Female Patients with Hashimoto's Thyroiditis Following Vitamin D Supplementation: A Double-blind, Randomized Clinical Trial

BACKGROUND

Hashimoto's thyroiditis (HT) is an autoimmune disease characterized by the destruction of thyroid cells through immune processes involving T helper (Th)1 cytokines. This clinical trial investigates the impact of vitamin D supplementation on serum cytokine levels and gene expression in CD4+ T cells from HT patients, aiming to understand its effects on Th-1, Th-2, Th-17, and regulatory T (Treg) cell-associated factors.

METHODS

Female patients were randomly assigned in a double-blind design to either a vitamin D-supplemented group, which received cholecalciferol (1, 25(OH)2D3) at a dose of 50,000 IU, or the placebo group, which received a weekly placebo for a duration of three months. Serum cytokine levels were assessed using enzyme-linked immunosorbent assay (ELISA), while genes' expression levels were measured using real-time PCR.

RESULTS

Serum 25-hydroxyvitamin D and levels exhibited a significant increase following vitamin D supplementation, in comparison to the placebo group. Additionally, the vitamin D supplementation resulted in a significant elevation of serum calcium (Ca) levels compared to baseline. In the vitamin D group, there was a significant decrease in both serum levels and expression of the interleukin (IL)-17 gene when compared to baseline, although no statistical difference was observed between the placebo and vitamin D groups. The gene expression of transforming growth factor-beta (TGFβ) was significantly increased in the vitamin D group compared to baseline, with no significant difference between the two study groups. Vitamin D treatment had no effect on serum levels of interferon-gamma (IFNϒ) and IL-4. While the gene expression of IL-4 in the vitamin D group did not exhibit a statistically significant increase, the level of GATA3 transcription factor increased significantly when compared to the placebo group. The expression of IFNϒ and transcription factors, T-bet, RORc, and forkhead box protein 3 (FOXP3) in genes did not show significant changes following vitamin D supplementation.

CONCLUSION

The findings suggest that vitamin D supplementation may hold potential benefits for autoimmune diseases, such as HT. However, further longitudinal clinical trials are necessary to gain a more comprehensive understanding of the specific effects of vitamin D on HT.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.

Tc17 cells in autoimmune diseases

ABSTRACT

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), a pathologically similar disease used to model MS in rodents, are typical CD4+ T cell-dominated autoimmune diseases. CD4+ interleukin (IL)17+ T cells (Th17 cells) have been well studied and have shown that they play a critical role in the pathogenesis of MS/EAE. However, studies have suggested that CD8+IL17+ T cells (Tc17 cells) have a similar phenotype and cytokine and transcription factor profiles to those of Th17 cells and have been found to be crucial in the pathogenesis of autoimmune diseases, including MS/EAE, psoriasis, type I diabetes, rheumatoid arthritis, and systemic lupus erythematosus. However, the evidence for this is indirect and insufficient. Therefore, we searched for related publications and attempted to summarize the current knowledge on the role of Tc17 cells in the pathogenesis of MS/EAE, as well as in the pathogenesis of other autoimmune diseases, and to find out whether Tc17 cells or Th17 cells play a more critical role in autoimmune disease, especially in MS and EAE pathogenesis, or whether the interaction between these two cell types plays a critical role in the development of the disease.

Targeting Immune Modulators in Glioma While Avoiding Autoimmune Conditions

Communication signals and signaling pathways are often studied in different physiological systems. However, it has become abundantly clear that the immune system is not self-regulated, but functions in close association with the nervous system. The neural-immune interface is complex; its balance determines cancer progression, as well as autoimmune disorders. Immunotherapy remains a promising approach in the context of glioblastoma multiforme (GBM). The primary obstacle to finding effective therapies is the potent immunosuppression induced by GBM. Anti-inflammatory cytokines, induction of regulatory T cells, and the expression of immune checkpoint molecules are the key mediators for immunosuppression in the tumor microenvironment. Immune checkpoint molecules are ligand-receptor pairs that exert inhibitory or stimulatory effects on immune responses. In the past decade, they have been extensively studied in preclinical and clinical trials in diseases such as cancer or autoimmune diseases in which the immune system has failed to maintain homeostasis. In this review, we will discuss promising immune-modulatory targets that are in the focus of current clinical research in glioblastoma, but are also in the precarious position of potentially becoming starting points for the development of autoimmune diseases like multiple sclerosis.

Immunoregulatory effects and therapeutic potential of vitamin D in multiple sclerosis

Initially recognised as an important factor for bone health, vitamin D is now known to have a range of effects on the immune system. Vitamin D deficiency is associated with an increased risk of multiple sclerosis (MS), a chronic immune-mediated demyelinating disease of the CNS. In this review, we explore the links between vitamin D deficiency, MS risk, and disease activity. We also discuss the known immune effects of vitamin D supplementation and the relevance of these observations to the immunopathology of MS. Finally, we review the existing evidence for vitamin D supplementation as an MS therapy, highlighting several recent clinical studies and trials.

Micronutrients in autoimmune diseases: possible therapeutic benefits of zinc and vitamin D

A functional immune system is essential for healthy life. This is achieved by the coordinate activation and interaction of different immune cells. One should be aware that activation of the immune response is as important as its deactivation when the pathogens are cleared, as otherwise host tissue can be damaged up to life-threatening levels. Autoimmune diseases (AID) represent a phenomenon of immune cells attacking host cells and tissue. Five to eight percent of the world's population are currently affected by 80-100 AID. In recent years, the incidence has been constantly increasing, reaching alarmingly high numbers particularly for type 1 diabetes mellitus, Crohn's disease, rheumatoid arthritis, Sjogren's syndrome and multiple sclerosis. This indicates a higher societal burden of AID for the future. This article provides an overview of general concepts of triggers and underlying mechanisms leading to self-destruction. Lately, several original concepts of disease etiology were revised, and there is a variety of hypotheses on triggers, underlying mechanisms and preventive actions. This article concentrates on the importance of nutrition, especially zinc and vitamin D, for balancing the immune function. Homespun nutritional remedies seem to reenter today's therapeutic strategies. Current treatment approaches are largely symptomatic or suppress the immune system. However, recent studies reveal significant benefits of nutrition-related therapeutic approaches including prevention and treatment of established disease, which offer a cost-efficient and trigger-unspecific alternative addressing balancing rather than suppression of the immune system. Zinc and vitamin D are currently the best studied and most promising candidates for therapeutic intervention.

Immune modulation by curcumin: The role of interleukin-10

Cytokines are small secreted proteins released by different types of cells with specific effects on cellular signaling and communication via binding to their receptors on the cell surface. IL-10 is known to be a pleiotropic and potent anti-inflammatory and immunosuppressive cytokine that is produced by both innate and adaptive immunity cells including dendritic cells, macrophages, mast cells, natural killer cells, eosinophils, neutrophils, B cells, CD8⁺ T cells, and T_H1, T_H2, and T_H17 and regulatory T cells. Both direct and indirect activation of the stress axis promotes IL-10 secretion. IL-10 deregulation plays a role in the development of a large number of inflammatory diseases such as neuropathic pain, Parkinson's disease, Alzheimer's disease, osteoarthritis, rheumatoid arthritis, psoriasis, systemic lupus erythematosus, type 1 diabetes, inflammatory bowel disease, and allergy. Curcumin is a natural anti-inflammatory compound able to induce the expression and production of IL-10 and enhancing its action on a large number of tissues. In vitro and in pre-clinical models curcumin is able to modulate the disease pathophysiology of conditions such as pain and neurodegenerative diseases, bowel inflammation, and allergy, but also of infections and cancer through its effect on IL-10 secretion. In humans, at least one part of the positive effects of curcumin on health could be related to its ability to enhance IL-10 -mediated effects.

Peripheral Tc17 and Tc17/Interferon-γ Cells are Increased and Associated with Lung Function in Patients with Chronic Obstructive Pulmonary Disease

Background:

Chronic obstructive pulmonary disease (COPD) is characterized by progressive loss of lung function and local and systemic inflammation, in which CD8⁺ T-cells are believed to play a key role. Activated CD8⁺ T-cells differentiate into distinct subpopulations, including interferon-γ (IFN-γ)-producing Tc1 and interleukin (IL)-17-producing Tc17 cells. Recent evidence indicates that Tc17 cells exhibit considerable plasticity and may convert into IL-17/IFN-γ-double producing (Tc17/IFN-γ) cells when driven by inflammatory conditions. The aim of this study was to investigate the Tc17/IFN-γ subpopulation in peripheral blood of patients with COPD and to evaluate their potential roles in this disease.

Methods:

Peripheral blood samples were collected from 15 never-smokers, 23 smokers with normal lung function, and 25 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease 2–4). Proportions of the IL-17/IFN-γ-double expressing subpopulation were assessed using flow cytometry. Plasma concentrations of cytokines favoring Tc17/IFN-γ differentiation were measured by enzyme-linked immunosorbent assay.

Results:

Patients with COPD had higher proportions of Tc17 cells and Tc17/IFN-γ cells in the peripheral blood than smokers and never-smokers. The plasticity of Tc17 cells was higher than that of Th17 cells. The percentages of Tc17 cells and Tc17/IFN-γ cells showed negative correlations with forced expiratory volume in 1 s % predicted value (r = −0.418, P = 0.03; r = −0.596, P = 0.002, respectively). The plasma concentrations of IL-6, transforming growth factor-β1, and IL-12 were significantly higher in patients with COPD compared with smokers and never-smokers.

Conclusions:

Peripheral Tc17 cells are increased and more likely to convert to Tc17/IFN-γ cells in COPD, suggesting that Tc17 cell plasticity may be involved in persistent inflammation of the disease.

Vitamin D in Autoimmunity: Molecular Mechanisms and Therapeutic Potential

Over the last three decades, it has become clear that the role of vitamin D goes beyond the regulation of calcium homeostasis and bone health. An important extraskeletal effect of vitamin D is the modulation of the immune system. In the context of autoimmune diseases, this is illustrated by correlations of vitamin D status and genetic polymorphisms in the vitamin D receptor with the incidence and severity of the disease. These correlations warrant investigation into the potential use of vitamin D in the treatment of patients with autoimmune diseases. In recent years, several clinical trials have been performed to investigate the therapeutic value of vitamin D in multiple sclerosis, rheumatoid arthritis, Crohn’s disease, type I diabetes, and systemic lupus erythematosus. Additionally, a second angle of investigation has focused on unraveling the molecular pathways used by vitamin D in order to find new potential therapeutic targets. This review will not only provide an overview of the clinical trials that have been performed but also discuss the current knowledge about the molecular mechanisms underlying the immunomodulatory effects of vitamin D and how these advances can be used in the treatment of autoimmune diseases.

Increased Proportion of Tc17 and Th17 Cells and Their Significant Reduction after Thymectomy May Be Related to Disease Progression in Myasthenia Gravis

OBJECTIVE

Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies against the neuromuscular junction. The thymus has an important role in the pathogenesis of MG because most patients have thymic pathology, and thymectomy (TE) can reduce the severity of the disease.

METHODS

In this study, the frequency of Th17 and Tc17 cells was studied in 12 MG patients (pre-TE and 6 months post-TE) and in 12 healthy controls (HC).

RESULTS

The frequency of Tc17 cells in the pre-TE patients was significantly higher than in the HC (p < 0.05), and after TE, these cells had significantly decreased compared to before TE (p < 0.05). The frequency of Th17 cells in pre-TE patients was significantly higher than in the HC (p < 0.05), and after TE, these cells had significantly decreased compared to before TE (p < 0.05).

CONCLUSION

Our findings indicated a possible role of Tc17 and Th17 in MG pathogenesis.

Circulating immune cells in multiple sclerosis

Circulating T and B lymphocytes contribute to the pathogenesis of the neuroinflammatory autoimmune disease, multiple sclerosis (MS). Further progress in the development of MS treatments is dependent upon a greater understanding of the immunological disturbances that underlie the disease. Analyses of circulating immune cells by flow cytometry have revealed MS-associated alterations in the composition and function of T and B cell subsets, including temporal changes associated with disease activity. Disturbances in circulating immune populations reflect those observed in the central nervous system and include skewing towards proinflammatory CD4⁺ and CD8⁺ T cells and B cells, greater proportions of follicular T helper cells and functional defects in the corresponding T and B regulatory subsets. Utilizing the analytical power of modern flow cytometers, researchers are now well positioned to monitor immunological changes associated with disease activity or intervention, describe immunological signatures with predictive value and identify targets for therapeutic drug development. This review discusses the contribution of various T and B lymphocyte subsets to MS pathogenesis, provides current and relevant phenotypical descriptions to assist in experimental design and highlights areas of future research.

Differential Frequency of CD8+ T Cell Subsets in Multiple Sclerosis Patients with Various Clinical Patterns

Recent evidence points to a pathogenic role for CD8⁺ cytotoxic T (Tc) cells in Multiple sclerosis (MS). Based on cytokine profile, Tc cells can be divided into different subsets: IFN-γ (Tc1), IL-4 (Tc2), IL-10 (Tc10), IL-17 (Tc17), IL-21 (Tc21), IL-22 (Tc22) and TNF-α producing cells. In this study we evaluated the frequency of Tc cell subsets and the serum level of Tc17 differentiation cytokines in MS patients with different clinical patterns. We analyzed Tc cell subsets percentage in peripheral blood of relapsing-remitting (RRMS) (n = 28), secondary-progressive (SPMS) (n = 10) and primary-progressive (PPMS) (n = 4) MS patients in comparison to healthy controls (n = 15) using flow cytometry. Serum level of TGF-β, IL-6 and IL-23 were measured by ELISA. We showed elevated levels of Tc1 and Tc17 cells in SPMS and RRMS patients in relapse phase, respectively (P = 0.04). Interestingly, the percentage of TNF-α producing CD8⁺ T cells in relapse and remission phase of RRMS and SPMS patients were higher than controls (P = 0.01, P = 0.004, P = 0.01, respectively) and Tc21 increased in remission phase of RRMS compared to SPMS (P = 0.03). We also found higher frequency of CD8⁺ IFN-γ⁺ TNF-α⁺ IL-17⁺ T cells in relapse phase of RRMS compared to remission phase, SPMS patients and controls (P = 0.01, P = 0.004 and P = 0.02, respectively). TGF- β increased in sera of RRMS patients in remission phase (P = 0.03) and SPMS (P = 0.05) compared to healthy subjects. Increased level of Tc17 and CD8⁺ IFN-γ⁺ TNF-α⁺ IL-17⁺ T cells in relapse phase highlights the critical role of IL-17 in RRMS pathogenesis.

Novel CD8+ T-Cell Subsets Demonstrating Plasticity in Patients with Inflammatory Bowel Disease

BACKGROUND

Distinct CD8+ T-cell subsets such as interleukin-17-expressing Tc17 and Foxp3-expressing Tcreg are functionally similar to CD4+ T cells. Though CD4+ T cells are dysregulated in patients with inflammatory bowel disease (IBD), CD8+ T cells are not well investigated. Vitamin D is an environmental factor which influences T-cell subsets. We assessed the prevalence of CD8+ T-cell subsets among peripheral blood mononuclear cells (PBMC) and lamina propria mononuclear cells (LPMC) of patients with Crohn's disease, patients with ulcerative colitis, and healthy controls. We then tested the effect of 1α,25-dihydroxyvitamin D3 on CD8+ T-cell subsets.

METHODS

A total of 73 patients with Crohn's disease, 49 patients with ulcerative colitis, and 47 healthy controls were studied. LPMC or PBMC were isolated and flow cytometry was performed. CD3+ T cells, isolated from PBMC, were cultured with or without 1α,25-dihydroxyvitamin D3, before flow cytometry.

RESULTS

In LPMC, the prevalence of Tcreg was higher in patients with IBD (P < 0.05), whereas Tc17 were higher in patients with ulcerative colitis compared with patients with Crohn's disease and healthy controls (P < 0.05). In PBMC, both Tcreg and Tc17 were higher in patients with IBD (P < 0.01). Double-expressing interferon-γ+ interleukin-17+ and Foxp3+ interleukin-17+ CD8+ T cells were also identified indicating possible CD8+ plasticity. 1α,25-dihydroxyvitamin D3 decreased interferon-γ-expressing Tc1 (P < 0.05), but had no effect on Tc17 or Tcreg.

CONCLUSIONS

The prevalence of novel CD8+ T-cell subsets is altered in patients with IBD. Double-expressing cells indicate plasticity and were identified in patients with IBD. Vitamin D may have a limited effect on CD8+ T cells by decreasing interferon-γ expression.

Seeking balance: Potentiation and inhibition of multiple sclerosis autoimmune responses by IL-6 and IL-10

The cytokines IL-6 and IL-10 are produced by cells of the adaptive and innate arms of the immune system and they appear to play key roles in genetically diverse autoimmune diseases such as relapsing remitting multiple sclerosis (MS), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Whereas previous intense investigations focused on the generation of autoantibodies and their contribution to immune-mediated pathogenesis in these diseases; more recent attention has focused on the roles of cytokines such as IL-6 and IL-10. In response to pathogens, antigen presenting cells (APC), including B cells, produce IL-6 and IL-10 in order to up-or down-regulate immune cell activation and effector responses. Evidence of elevated levels of the proinflammatory cytokine IL-6 has been routinely observed during inflammatory responses and in a number of autoimmune diseases. Our recent studies suggest that MS peripheral blood B cells secrete higher quantities of IL-6 and less IL-10 than B cells from healthy controls. Persistent production of IL-6, in turn, contributes to T cell expansion and the functional hyperactivity of APC such as MS B cells. Altered B cell activity can have a profound impact on resultant T cell effector functions. Enhanced signaling through the IL-6 receptor can effectively inhibit cytolytic activity, induce T cell resistance to IL-10-mediated immunosuppression and increase skewing of autoreactive T cells to a pathogenic Th17 phenotype. Our recent findings and studies by others support a role for the indirect attenuation of B cell responses by Glatiramer acetate (GA) therapy. Our studies suggest that GA therapy temporarily permits homeostatic regulatory mechanisms to be reinstated. Future studies of mechanisms underlying dysregulated B cell cytokine production could lead to the identification of novel targets for improved immunoregulatory therapies for autoimmune diseases.

IL-17A-producing CD8(+)T cells as therapeutic targets in autoimmunity

INTRODUCTION

The involvement of IL-17-producing CD8(+)T cells (TC17) in various conditions, such as infection, cancer and autoimmune inflammation, has been documented in both humans and mice; however, TC17 cells have received only marginal attention.

AREAS COVERED

Here, we provide an overview of the cytokines, chemokines, and cytokine and chemokine receptors that characterize the murine and human TC17 cell phenotype. We also discuss signaling pathways, molecular interactions, and transcriptional and epigenetic events that contribute to TC17 differentiation and acquisition of effector functions. Heterogeneity and inherent phenotypic instability of TC17 cells were shown both in humans and murine models. Aberrant expression of TC17 cells was observed in many autoimmune conditions. Moreover, functional analysis demonstrated in vivo plasticity of TC17 cells may be a key feature of TC17 cell biology in autoimmune diseases.

EXPERT OPINION

Due to its important roles in inflammation and autoimmunity, TC17 cell pathway may have promise as a potential therapeutic target for autoimmune diseases. The strategies include the suppression of TC17 cell generation and migration and the blockade of TC17 cell instability and heterogeneity. TMP778 may open an avenue to novel therapeutic strategies.

M1 and M2 immune activation in Parkinson's Disease: Foe and ally?

Parkinson's Disease (PD) is a chronic and progressive neurodegenerative disorder of unknown etiology. Autopsy findings, genetics, retrospective studies, and molecular imaging all suggest a role for inflammation in the neurodegenerative process. However, relatively little is understood about the causes and implications of neuroinflammation in PD. Understanding how inflammation arises in PD, in particular the activation state of cells of the innate immune system, may provide an exciting opportunity for novel neuroprotective therapeutics. We analyze the evidence of immune system involvement in PD susceptibility, specifically in the context of M1 and M2 activation states. Tracking and modulating these activation states may provide new insights into both PD etiology and therapeutic strategies.

Tc17 Cells in Immunity and Systemic Autoimmunity

Tc17 cells-a subset of CD8(+)T cells-have recently been identified that are characterized by the production of interleukin (IL)-17. Cytokines IL-6 and transforming growth factor-beta 1 (TGF-β1) and transcription factors signaling transducers and activators of transcription (STAT)3, retinoic acid receptor-related orphan nuclear receptor gamma (RORγt), and interferon regulatory factor (IRF)4 are necessary for differentiation of Tc17 cells, controlling expression of molecules essential for Tc17 cell trafficking and function. Current human researches have determined the significance of CD161 expression as either a marker of Tc17 cells or as an effector and regulator of Tc17 cell function. Noncytotoxic Tc17 cells possess a high plasticity to convert into IFN-γ producing cells, which exhibit strong cytotoxic activity. The importance of in vivo plasticity of Tc17 cells for the induction of autoimmune diseases has been demonstrated and Tc17 cells potentially represent novel therapeutic targets in autoimmune diseases. The involvement of interleukin (IL)-17-producing CD8(+)T cells (Tc17) in various conditions, such as infection, cancer, and autoimmune inflammation, has been documented in both humans and mice; however, Tc17 cells have received only marginal attention. Here, we provide an overview of the cytokines and chemokines that characterize the murine and human Tc17 cells. Moreover, we discuss signaling pathways, molecular interactions, and transcriptional events that contribute to Tc17 differentiation and acquisition of effector functions. Also considered is the basis of Tc17 cell plasticity toward the Tc1 lineage, and we suggest that in vivo plasticity of Tc17 cells may be a key feature of Tc17 cell biology in autoimmune diseases. Furthermore, current human researches have revealed that Tc17 cells are different than that in mice because all of them express CD161 and exclusively originate from CD161 precursors present in umbilical cord blood. Finally, we focus on the recent evidence for long-lived Tc17 memory cell populations in mouse models and humans, and their functional roles in mediating disease memory. Hopefully, the information obtained will benefit for developing novel therapeutic strategies.