CD4+ T-Cell Plasticity in Non-Infectious Retinal Inflammatory Disease

Non-infectious uveitis (NIU) is a potentially sight-threatening disease. Effector CD4⁺ T cells, especially interferon-γ-(IFNγ) producing Th1 cells and interleukin-17-(IL-17) producing Th17 cells, are the major immunopathogenic cells, as demonstrated by adoptive transfer of disease in a model of experimental autoimmune uveitis (EAU). CD4⁺FoxP3⁺CD25⁺ regulatory T cells (Tregs) were known to suppress function of effector CD4⁺ T cells and contribute to resolution of disease. It has been recently reported that some CD4⁺ T-cell subsets demonstrate shared phenotypes with another CD4⁺ T-cell subset, offering the potential for dual function. For example, Th17/Th1 (co-expressing IFNγ and IL-17) cells and Th17/Treg (co-expressing IL-17 and FoxP3) cells have been identified in NIU and EAU. In this review, we have investigated the evidence as to whether these ‘plastic CD4⁺ T cells’ are functionally active in uveitis. We conclude that Th17/Th1 cells are generated locally, are resistant to the immunosuppressive effects of steroids, and contribute to early development of EAU. Th17/Treg cells produce IL-17, not IL-10, and act similar to Th17 cells. These cells were considered pathogenic in uveitis. Future studies are needed to better clarify their function, and in the future, these cell subsets may in need to be taken into consideration for designing treatment strategies for disease.     

Mycobacterium tuberculosis RpfE-Induced Prostaglandin E2 in Dendritic Cells Induces Th1/Th17 Cell Differentiation

Prostaglandin E2 (PGE2) is an important biological mediator involved in the defense against Mycobacterium tuberculosis (Mtb) infection. Currently, there are no reports on the mycobacterial components that regulate PGE2 production. Previously, we have reported that RpfE-treated dendritic cells (DCs) effectively expanded the Th1 and Th17 cell responses simultaneously; however, the mechanism underlying Th1 and Th17 cell differentiation is unclear. Here, we show that PGE2 produced by RpfE-activated DCs via the MAPK and cyclooxygenase 2 signaling pathways induces Th1 and Th17 cell responses mainly via the EP4 receptor. Furthermore, mice administered intranasally with PGE2 displayed RpfE-induced antigen-specific Th1 and Th17 responses with a significant reduction in bacterial load in the lungs. Furthermore, the addition of optimal PGE2 amount to IL-2-IL-6-IL-23p19-IL-1β was essential for promoting differentiation into Th1/Th17 cells with strong bactericidal activity. These results suggest that RpfE-matured DCs produce PGE2 that induces Th1 and Th17 cell differentiation with potent anti-mycobacterial activity.     

The PI-3-Kinase P110α Catalytic Subunit of T Lymphocytes Modulates Collagen-Induced Arthritis

The phosphatidylinositol 3-kinase (PI3K) family of enzymes plays a determinant role in inflammation and autoimmune responses. However, the implication of the different isoforms of catalytic subunits in these processes is not clear. Rheumatoid arthritis (RA) is a chronic, systemic autoimmune inflammatory disease that entails innate and adaptive immune response elements in which PI3K is a potential hub for immune modulation. In a mouse transgenic model with T-cell-specific deletion of p110α catalytic chain (p110α^−/−ΔT), we show the modulation of collagen-induced arthritis (CIA) by this isoform of PI3K. In established arthritis, p110α^−/−ΔT mice show decreased prevalence of illness than their control siblings, higher IgG1 titers and lower levels of IL-6 in serum, together with decreased ex vivo Collagen II (CII)-induced proliferation, IL-17A secretion and proportion of naive T cells in the lymph nodes. In a pre-arthritis phase, at 13 days post-Ag, T-cell-specific deletion of p110α chain induced an increased, less pathogenic IgG1/IgG2a antibodies ratio; changes in the fraction of naive and effector CD4⁺ subpopulations; and an increased number of CXCR5⁺ T cells in the draining lymph nodes of the p110α^−/−ΔT mice. Strikingly, T-cell blasts in vitro obtained from non-immunized p110α^−/−ΔT mice showed an increased expression of CXCR5, CD44 and ICOS surface markers and defective ICOS-induced signaling towards Akt phosphorylation. These results, plus the accumulation of cells in the lymph nodes in the early phase of the process, could explain the diminished illness incidence and prevalence in the p110α^−/−ΔT mice and suggests a modulation of CIA by the p110α catalytic chain of PI3K, opening new avenues of intervention in T-cell-directed therapies to autoimmune diseases.     

CD147 Is Essential for the Development of Psoriasis via the Induction of Th17 Cell Differentiation

Th17 cells play an important role in psoriasis. The differentiation of naïve CD4⁺ T cells into Th17 cells depends on glycolysis as the energy source. CD147/basigin, an integral transmembrane protein belonging to the immunoglobulin superfamily, regulates glycolysis in association with monocarboxylate transporters (MCTs)-1 and -4 in cancer cells and T cells. We examined whether CD147/basigin is involved in the pathogenesis of psoriasis in humans and psoriasis-model mice. The serum level of CD147 was increased in patients with psoriasis, and the expression of CD147 and MCT-1 was elevated in their dermal CD4⁺ RORγt⁺ T cells. In vitro, the potential of naïve CD4⁺ T cells to differentiate into Th17 cells was abrogated in CD147^−/− T cells. Imiquimod (IMQ)-induced psoriatic dermatitis was significantly milder in CD147^−/− mice and bone marrow chimeric mice lacking CD147 in the hematopoietic cells of myeloid lineage. These findings demonstrate that CD147 is essential for the development of psoriasis via the induction of Th17 cell differentiation.     

Oral Administration of Bovine Milk from Cows Hyperimmunized with Intestinal Bacterin Stimulates Lamina Propria T Lymphocytes to Produce Th1-Biased Cytokines in Mice

The goal of this study was to examine the effects of oral administration of bovine milk from cows hyperimmunized with a proprietary bacterin (immune milk “Sustaina”) on mucosal immunity in the intestine of adult mice. C57BL/6 mice were orally given immune or control milk for two weeks, and then lymphocyte population and the cytokine production in lamina propria of colon in normal mice and mice induced colitis by dextran sulphate sodium (DSS) were detected. We found that the levels of IFN-γ and IL-10 increased, but the levels of IL-17A and IL-4, decreased in lamina propria of colon in immune milk-fed mice as compared with those in control milk-fed mice. Interestingly, oral administration of immune milk partially improved the acute colitis induced by DSS. The levels of TNF-α and IFN-γ increased, but IL-6, IL-17A and IL-4 decreased in lamina propria (LP) of colon in immune milk-fed mice with DSS-induced colitis. Our results suggest that immune milk may stimulate CD4⁺ T cells to polarize towards a Th1 type response, but contrarily suppress Th17 and Th2 cells responses in large intestinal LP of mice. The results indicate that this kind of immune milk has is able to promote the maintainance of intestinal homeostasis and enhance protection against infection, and could alleviate the symptoms of acute colitis in mice.     

Cord Blood T Cells Expressing High and Low PKCζ Levels Develop into Cells with a Propensity to Display Th1 and Th9 Cytokine Profiles,Respectively

Low Protein Kinase C zeta (PKCζ) levels in cord blood T cells (CBTC) have been shown to correlate with the development of allergic sensitization in childhood. However, little is known about the mechanisms responsible. We have examined the relationship between the expression of different levels of PKCζ in CBTC and their development into mature T cell cytokine producers that relate to allergy or anti-allergy promoting cells. Maturation of naïve CBTC was initiated with anti-CD3/-CD28 antibodies and recombinant human interleukin-2 (rhIL-2). To stimulate lymphocyte proliferation and cytokine production the cells were treated with Phytohaemagglutinin (PHA) and Phorbol myristate acetate (PMA). Irrespective of the PKCζ levels expressed, immature CBTC showed no difference in lymphocyte proliferation and the production of T helper 2 (Th2) cytokine interleukin-4 (IL-4) and Th1 cytokine, interferon-gamma (IFN-γ), and influenced neither their maturation from CD45RA⁺ to CD45RO⁺ cells nor cell viability/apoptosis. However, upon maturation the low PKCζ expressing cells produced low levels of the Th1 cytokines, IFN-γ, IL-2 and tumour necrosis factor-alpha (TNF), no changes to levels of the Th2 cytokines, IL-4, IL-5 and IL-13, and an increase in the Th9 cytokine, IL-9. Other cytokines, lymphotoxin-α (LT-α), IL-10, IL-17, IL-21, IL-22 and Transforming growth factor-beta (TGF-β) were not significantly different. The findings support the view that low CBTC PKCζ levels relate to the increased risk of developing allergic diseases.     

Ubiquitous Overexpression of Chromatin Remodeling Factor SRG3 Exacerbates Atopic Dermatitis in NC/Nga Mice by Enhancing Th2 Immune Responses

The SWItch (SWI)3-related gene (SRG3) product, a SWI/Sucrose Non-Fermenting (SNF) chromatin remodeling subunit, plays a critical role in regulating immune responses. We have previously shown that ubiquitous SRG3 overexpression attenuates the progression of Th1/Th17-mediated experimental autoimmune encephalomyelitis. However, it is unclear whether SRG3 overexpression can affect the pathogenesis of inflammatory skin diseases such as atopic dermatitis (AD), a Th2-type immune disorder. Thus, to elucidate the effects of SRG3 overexpression in AD development, we bred NC/Nga (NC) mice with transgenic mice where SRG3 expression is driven by the β-actin promoter (SRG3^β-actin mice). We found that SRG3^β-actin NC mice exhibit increased AD development (e.g., a higher clinical score, immunoglobulin E (IgE) hyperproduction, and an increased number of infiltrated mast cells and basophils in skin lesions) compared with wild-type NC mice. Moreover, the severity of AD pathogenesis in SRG3^β-actin NC mice correlated with expansion of interleukin 4 (IL4)-producing basophils and mast cells, and M2 macrophages. Furthermore, this accelerated AD development is strongly associated with Treg cell suppression. Collectively, our results have identified that modulation of SRG3 function can be applied as one of the options to control AD pathogenesis.     

Peritoneal Fluid from Patients with Ovarian Endometriosis Displays Immunosuppressive Potential and Stimulates Th2 Response

Endometriosis is a common gynaecological disorder characterized by the ectopic growth of endometrial tissue outside the uterine cavity. It is associated with chronic pelvic inflammation and autoimmune reactivity manifesting by autoantibody production and abrogated cellular immune responses. Endometriotic peritoneal fluid contains various infiltrating leucocyte populations and a bulk of proinflammatory and immunoregulatory cytokines. However, the nature and significance of the peritoneal milieu in women with endometriosis still remains obscure. Therefore, the aim of the present study was to investigate the immunoregulatory activity of the peritoneal fluid (PF) from women with endometriosis. The peritoneal fluid samples were collected during laparoscopic surgery from 30 women with and without endometriosis. Immunoregulatory cytokines (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ and TNF) and chemokines (CCL2, CCL5, CXCL8 and CXCL9) were evaluated in PF and culture supernatants generated by unstimulated and CD3/CD28/IL-2-stimulated CD4⁺ T cells cultured in the presence of PF. The effect of PF on the generation of Treg and Th17 cells in CD4⁺ T cell cultures, as well as the natural cytotoxic activity of peripheral blood mononuclear cells, was also investigated. Concentrations of IL-6, IL-10, CCL2, CXCL8 and CXCL9 were significantly upregulated in the PF from women with endometriosis when compared to control women, whereas concentrations of other cytokines and chemokines were unaffected. The culturing of unstimulated and CD3/CD28/IL-2-stimulated CD4⁺ T cells in the presence of endometriotic PF resulted in the downregulation of their IL-2, IFN-γ, IL-17A and TNF production as compared to culture medium alone. On the other side, endometriotic PF significantly stimulated the production of IL-4 and IL-10. Endometriotic PF also stimulated the release of CCL2 and CXCL8, whereas the production of CCL5 and CXCL9 was downregulated. Endometriotic PF stimulated the generation of Treg cells and had an inhibitory effect on the generation of Th17 cells in cultures of CD4⁺ T cells. It also inhibited the NK cell cytotoxic activity of the peripheral blood lymphocytes. These results strongly imply that the PF from patients with endometriosis has immunoregulatory/immunosuppressive activity and shifts the Th1/Th2 cytokine balance toward the Th2 response, which may account for deviation of local and systemic immune responses. However, a similar trend, albeit not a statistically significant one, was also observed in case of PF from women without endometriosis, thus suggesting that peritoneal milieu may in general display some immunoregulatory/immunosuppressive properties. It should be stressed, however, that our present observations were made on a relatively small number of PF samples and further studies are needed to reveal possible mechanism(s) responsible for this phenomenon.     

Hedgehog Signalling Modulates Immune Response and Protects against Experimental Autoimmune Encephalomyelitis

The Hedgehog (Hh) pathway is essential for the embryonic development and homeostatic maintenance of many adult tissues and organs. It has also been associated with some functions of the innate and adaptive immune system. However, its involvement in the immune response has not been well determined. Here we study the role of Hh signalling in the modulation of the immune response by using the Ptch-1-LacZ^+/− mouse model (hereinafter referred to as ptch^+/−), in which the hemizygous inactivation of Patched-1, the Hh receptor gene, causes the constitutive activation of Hh response genes. The in vitro TCR stimulation of spleen and lymph node (LN) T cells showed increased levels of Th2 cytokines (IL-4 and IL-10) in ptch^+/−cells compared to control cells from wild-type (wt) littermates, suggesting that the Th2 phenotype is favoured by Hh pathway activation. In addition, CD4⁺ cells secreted less IL-17, and the establishment of the Th1 phenotype was impaired in ptch^+/− mice. Consistently, in response to an inflammatory challenge by the induction of experimental autoimmune encephalomyelitis (EAE), ptch^+/− mice showed milder clinical scores and more minor spinal cord damage than wt mice. These results demonstrate a role for the Hh/ptch pathway in immune response modulation and highlight the usefulness of the ptch^+/− mouse model for the study of T-cell-mediated diseases and for the search for new therapeutic strategies in inflammatory diseases.     

Kurarinone Attenuates Collagen-Induced Arthritis in Mice by Inhibiting Th1/Th17 Cell Responses and Oxidative Stress

Kurarinone is a flavanone, extracted from Sophora flavescens Aiton, with multiple biological effects. Here, we determine the therapeutic potential of kurarinone and elucidate the interplay between kurarinone and the autoimmune disease rheumatoid arthritis (RA). Arthritis was recapitulated by induction of bovine collagen II (CII) in DBA/1 mice as a collagen-induced arthritis (CIA) model. After the establishment of the CIA, kurarinone was given orally from day 21 to 42 (100 mg/kg/day) followed by determination of the severity based on a symptom scoring scale and with histopathology. Levels of cytokines, anti-CII antibodies, and the proliferation and lineages of T cells from the draining lymph nodes were measured using ELISA and flow cytometry, respectively. The expressional changes, including STAT1, STAT3, Nrf2, KEAP-1, and heme oxygenase-1 (HO-1) changes in the paw tissues, were evaluated by Western blot assay. Oxidative stress featured with malondiadehyde (MDA) and hydrogen peroxide (H₂O₂) activities in paw tissues were also evaluated. Results showed that kurarinone treatment reduced arthritis severity of CIA mice, as well as their levels of proinflammatory cytokines, TNF-α, IL-6, IFN-γ, and IL-17A, in the serum and paw tissues. T cell proliferation was also reduced by kurarinone even under the stimulation of CII and anti-CD3 antibody. In addition, kurarinone reduced STAT1 and STAT3 phosphorylation and the proportions of Th1 and Th17 cells in lymph nodes. Moreover, kurarinone suppressed the production of MDA and H₂O_2. All while promoting enzymatic activities of key antioxidant enzymes, SOD and GSH-Px. In the paw tissues, upregulation of Nrf-2 and HO-1, and downregulation of KEAP-1 were observed. Overall, kurarinone showed an anti-inflammatory effect by inhibiting Th1 and Th17 cell differentiation and an antioxidant effect exerted in part through activating the Nrf-2/KEAP-1 pathway. These beneficial effects in CIA mice contributed to the amelioration of their arthritis, indicating that kurarinone might be an adjunct treatment option for rheumatoid arthritis.     

Sex-Based Selectivity of PPARγ Regulation in Th1, Th2, and Th17 Differentiation

Peroxisome proliferator-activated receptor gamma (PPARγ) has recently been recognized to regulate adaptive immunity through Th17 differentiation, Treg functions, and T_FH responses. However, its role in adaptive immunity and autoimmune disease is still not clear, possibly due to sexual differences. Here, we investigated in vitro treatment study with the PPARγ agonist pioglitazone to compare Th1, Th2, and Th17 differentiation in male and female mouse splenic T cells. Pioglitazone treatment significantly inhibited various effector T cell differentiations including Th1, Th2, and Th17 cells from female naïve T cells, but it selectively reduced IL-17 production in male Th17 differentiation. Interestingly, pioglitazone and estradiol (E2) co-treatment of T cells in males inhibited differentiation of Th1, Th2, and Th17 cells, suggesting a mechanism for the greater sensitivity of PPARγ to ligand treatment in the regulation of effector T cell differentiation in females. Collectively, these results demonstrate that PPARγ selectively inhibits Th17 differentiation only in male T cells and modulates Th1, Th2, and Th17 differentiation in female T cells based on different level of estrogen exposure. Accordingly, PPARγ could be an important immune regulator of sexual differences in adaptive immunity.     

Recruitment of M1 Macrophages May Not Be Critical for Protection against Colitis-Associated Tumorigenesis

A close connection between inflammation and the risk of developing colon cancer has been suggested in the last few years. It has been estimated that patients diagnosed with some types of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease, have up to a 30% increased risk of developing colon cancer. However, there is also evidence showing that the activation of anti-inflammatory pathways, such as the IL-4 receptor-mediated pathway, may favor the development of colon tumors. Using an experimental model of colitis-associated colon cancer (CAC), we found that the decrease in tumor development in global IL4Rα knockout mice (IL4RαKO) was apparently associated with an inflammatory response mediated by the infiltration of M1 macrophages (F480⁺TLR2⁺STAT1⁺) and iNOS expression in colon tissue. However, when we developed mice with a specific deletion of IL4Rα in macrophages (LysMcreIL4Rα^−/lox mice) and subjected them to CAC, it was found that despite presenting a large infiltration of M1 macrophages into the colon, these mice were as susceptible to colon-tumorigenesis as WT mice. These data suggest that in the tumor microenvironment the absence of IL4Rα expression on macrophages, as well as the recruitment of M1 macrophages, may not be directly associated with resistance to developing colon tumors. Therefore, it is possible that IL4Rα expression in other cell types, such as colonic epithelial cells, could have an important role in promoting the development of colitis-associated colon tumorigenesis.     

The Dual Role of the β2-Adrenoreceptor in the Modulation of IL-17 and IFN-γ Production by T Cells in Multiple Sclerosis

Norepinephrine is a neurotransmitter that also has an immunomodulatory effect and is involved in multiple sclerosis (MS) pathogenesis. This study aimed to clarify the role of the β₂-adrenoreceptor in the norepinephrine-mediated modulation of interleukin-17 (IL-17) and interferon-γ (IFN-γ) production, which play a critical pathogenetic role in MS. CD4⁺ T cells obtained from twenty-five relapsing-remitting MS patients and sixteen healthy subjects were cultured ex vivo with norepinephrine and/or β₂-adrenoreceptor antagonist or agonist, followed by a cytokine production analysis using ELISA. Norepinephrine suppressed IL-17 and IFN-γ production by the anti-CD3/anti-CD28-microbead-stimulated CD4⁺ T cells in both groups. Blockade of the β₂-adrenoreceptor with the specific antagonist ICI 118.551 enhanced norepinephrine-mediated IL-17 suppression but decreased its inhibitory effect on IFN-γ production in MS patients. In contrast, the β₂-adrenoreceptor agonist formoterol did not influence norepinephrine’s inhibitory effect on cytokine production in both groups. The blockade of the β₂-adrenoreceptor, even in the absence of exogenous norepinephrine, suppressed IL-17 production but did not influence IFN-γ production in both groups. Conversely, β₂-adrenoreceptor activation by formoterol decreased IFN-γ production and did not affect IL-17 production in both groups. These data illustrate the inhibitory effect of norepinephrine on IL-17 and IFN-γ production by CD4⁺ T cells in MS. The inhibitory effect of norepinephrine on IFN-γ production by CD4⁺ T cells in MS could be mediated via β₂-adrenoreceptor activation.     

Interferon Lambda Regulates Cellular and Humoral Immunity in Pristane-Induced Lupus

A pivotal role of type I interferons in systemic lupus erythematosus (SLE) is widely accepted. Type III interferons (IFN-λ) however, the most recently discovered cytokines grouped within the interferon family, have not been extensively studied in lupus disease models yet. Growing evidence suggests a role for IFN-λ in regulating both innate and adaptive immune responses, and increased serum concentrations have been described in multiple autoimmune diseases including SLE. Using the pristane-induced lupus model, we found that mice with defective IFN-λ receptors (Ifnlr1^−/−) showed increased survival rates, decreased lipogranuloma formation and reduced anti-dsDNA autoantibody titers in the early phase of autoimmunity development compared to pristane-treated wild-type mice. Moreover, Ifnlr1^−/− mice treated with pristane had reduced numbers of inflammatory mononuclear phagocytes and cNK cells in their kidneys, resembling untreated control mice. Systemically, circulating B cells and monocytes (CD115⁺Ly6C⁺) were reduced in pristane-treated Ifnlr1^−/− mice. The present study supports a significant role for type III interferons in the pathogenesis of pristane-induced murine autoimmunity as well as in systemic and renal inflammation. Although the absence of type III interferon receptors does not completely prevent the development of autoantibodies, type III interferon signaling accelerates the development of autoimmunity and promotes a pro-inflammatory environment in autoimmune-prone hosts.     

Role of iRhoms 1 and 2 in Endochondral Ossification

Growth of the axial and appendicular skeleton depends on endochondral ossification, which is controlled by tightly regulated cell–cell interactions in the developing growth plates. Previous studies have uncovered an important role of a disintegrin and metalloprotease 17 (ADAM17) in the normal development of the mineralized zone of hypertrophic chondrocytes during endochondral ossification. ADAM17 regulates EGF-receptor signaling by cleaving EGFR-ligands such as TGFα from their membrane-anchored precursor. The activity of ADAM17 is controlled by two regulatory binding partners, the inactive Rhomboids 1 and 2 (iRhom1, 2), raising questions about their role in endochondral ossification. To address this question, we generated mice lacking iRhom2 (iR2−/−) with floxed alleles of iRhom1 that were specifically deleted in chondrocytes by Col2a1-Cre (iR1∆Ch). The resulting iR2−/−iR1∆Ch mice had retarded bone growth compared to iR2−/− mice, caused by a significantly expanded zone of hypertrophic mineralizing chondrocytes in the growth plate. Primary iR2−/−iR1∆Ch chondrocytes had strongly reduced shedding of TGFα and other ADAM17-dependent EGFR-ligands. The enlarged zone of mineralized hypertrophic chondrocytes in iR2−/−iR1∆Ch mice closely resembled the abnormal growth plate in A17∆Ch mice and was similar to growth plates in Tgfα−/− mice or mice with EGFR mutations. These data support a model in which iRhom1 and 2 regulate bone growth by controlling the ADAM17/TGFα/EGFR signaling axis during endochondral ossification.     

Human CD4+CD45RA+ T Cells Behavior after In Vitro Activation: Modulatory Role of Vasoactive Intestinal Peptide

Naїve CD4⁺ T cells, which suffer different polarizing signals during T cell receptor activation, are responsible for an adequate immune response. In this study, we aimed to evaluate the behavior of human CD4⁺CD45RA⁺ T cells after in vitro activation by anti-CD3/CD28 bead stimulation for 14 days. We also wanted to check the role of the VIP system during this process. The metabolic biomarker Glut1 was increased, pointing to an increase in glucose requirement whereas Hif-1α expression was higher in resting than in activated cells. Expression of Th1 markers increased at the beginning of activation, whereas Th17-associated biomarkers augmented after that, showing a pathogenic Th17 profile with a possible plasticity to Th17/1. Foxp3 mRNA expression augmented from day 4, but no parallel increases were observed in IL-10, IL-2, or TGFβ mRNA expression, meaning that these potential differentiated Treg could not be functional. Both VIP receptors were located on the plasma membrane, and expression of VPAC₂ receptor increased significantly with respect to the VPAC₁ receptor from day 4 of CD4⁺CD45RA⁺ T activation, pointing to a shift in VPAC receptors. VIP decreased IFNγ and IL-23R expression during the activation, suggesting a feasible modulation of Th17/1 plasticity and Th17 stabilization through both VPAC receptors. These novel results show that, without polarizing conditions, CD4⁺CD45RA⁺ T cells differentiate mainly to a pathogenic Th17 subset and an unpaired Treg subset after several days of activation. Moreover, they confirm the important immunomodulatory role of VIP, also on naїve Th cells, stressing the importance of this neuropeptide on lymphocyte responses in different pathological or non-pathological situations.