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T helper (Th) 17 cells represent a novel subset of CD4+ T cells that are protective against extracellular microbes, but are responsible for autoimmune disorders in mice. However, their properties in humans are only partially known. We demonstrate the presence of Th17 cells, some of which produce both interleukin (IL)-17 and interferon (IFN)-gamma (Th17/Th1), in the gut of patients with Crohn's disease. Both Th17 and Th17/Th1 clones showed selective expression of IL-23R, CCR6, and the transcription factor ROR gamma t, and they exhibited similar functional features, such as the ability to help B cells, low cytotoxicity, and poor susceptibility to regulation by autologous regulatory T cells. Interestingly, these subsets also expressed the Th1-transcription factor T-bet, and stimulation of these cells in the presence of IL-12 down-regulated the expression of ROR gamma t and the production of IL-17, but induced IFN-gamma. These effects were partially inhibited in presence of IL-23. Similar receptor expression and functional capabilities were observed in freshly derived IL-17-producing peripheral blood and tonsillar CD4+ T cells. The demonstration of selective markers for human Th17 cells may help us to understand their pathogenic role. Moreover, the identification of a subset of cells sharing features of both Th1 and Th17, which can arise from the modulation of Th17 cells by IL-12, may raise new issues concerning developmental and/or functional relationships between Th17 and Th1.

Background The clinical efficacy and safety of sublingual immunotherapy (SLIT) for aeroallergens has been demonstrated in several trials, whereas the immunological changes induced by this treatment, which may account for the clinical improvement, are still unclear. Objective To investigate the effects of a successful SLIT on the in vitro allergen-driven T cell response and cytokine secretion as well as on the serum levels of chemokines and of IgE, IgG1 and IgG4 antibodies (Abs). Materials and methods Twenty-five Dermatophagoides pteronyssinus (Dp)-sensitive patients with perennial rhinitic and/or rhinitic and asthmatic symptoms were randomized into two groups (13 untreated (UT) and 12 SLIT-treated) for a 1 year and half study. The proliferative response of peripheral blood mononuclear cell (PBMC) to purified Der p1 allergen, their cytokines (IFN-gamma, IL-4, IL-10 and TGF-beta) production and serum levels of chemokines associated with T helper type 1 (Th1) (CXCL10) or T helper type 2 (Th2) (CCL22) responses and of Dp-specific IgE, IgG1 and IgG4 Abs were evaluated before and after 6 months of treatment. Results SLIT induced a significant reduction of symptom medication scores after 6, 12 and 18 months of treatment in comparison with UT patients. SLIT-treated patients showed a significant decrease in serum levels of DP-specific IgE Abs, whereas total IgE, and specific IgG1 and IgG4 Abs remained unchanged. The proliferative response of allergen-specific T cells to Der p1 in vitro after 6 months of treatment was reduced, while no effect was observed on T cell proliferation to recall antigen (streptokinase). Moreover, Der p1-driven IFN-gamma and IL-10 were significantly increased in culture supernatants of PBMC from 6 month-treated patients in comparison with those detected at the beginning of therapy. Conclusions These data suggest that the allergen-driven enhancement of IL-10- and IFN-gamma-producing T cells precedes and associates with SLIT-induced down-regulation of specific IgE, thus providing a rationale to explain the clinical benefit of SLIT in allergic patients.

Human Th17 clones and circulating Th17 cells showed lower susceptibility to the anti-proliferative effect of TGF-beta than Th1 and Th2 clones or circulating Th1-oriented T cells, respectively. Accordingly, human Th17 cells exhibited lower expression of clusterin, and higher Bcl-2 expression and reduced apoptosis in the presence of TGF-beta, in comparison with Th1 cells. Umbilical cord blood naïve CD161(+)CD4(+) T cells, which contain the precursors of human Th17 cells, differentiated into IL-17A-producing cells only in response to IL-1beta plus IL-23, even in serum-free cultures. TGF-beta had no effect on constitutive RORgamma t expression by umbilical cord blood CD161(+) T cells but it increased the relative proportions of CD161(+) T cells differentiating into Th17 cells in response to IL-1beta plus IL-23, whereas under the same conditions it inhibited both T-bet expression and Th1 development. These data suggest that TGF-beta is not critical for the differentiation of human Th17 cells, but indirectly favors their expansion because Th17 cells are poorly susceptible to its suppressive effects.

Objective To investigate the phenotype and function of CD4+ T cells in synovial fluid (SF) from the affected joints of children with oligoarticular-onset juvenile idiopathic arthritis (JIA), and to establish a possible link with disease activity. Methods CD4+ T cells were obtained from the peripheral blood (PB) and SF of 23 children with oligoarticular-onset JIA, as well as from the PB of 15 healthy children. The cells were analyzed for the expression of CXCR3, CCR6, and CD161 and for the production of interferon-Î and interleukin-17A (IL-17A). Spectratyping and clonotype analyses were performed to assess different T cell subsets. Results The numbers of CD4+CD161+ cells showing either the Th1 or the Th17/Th1 phenotype were higher in the SF than in the PB of children with JIA. The few Th17 cells from JIA SF underwent a spontaneous shift to the Th1 phenotype in vitro, whereas Th17 cells from the PB of healthy children shifted only in the presence of JIA SF; this effect was neutralized by antibody blockade of IL-12 activity. Spectratyping and clonotype analyses showed a similar skewing of the T cell receptor V β repertoire in both CD161+ Th17 cells and CD161+ Th1 cells derived from the SF of the same JIA patient. The frequencies of CD4+CD161+ cells, particularly the Th17/Th1 cells, in the JIA SF positively correlated with the erythrocyte sedimentation rate and levels of C-reactive protein. Conclusion These findings suggest that a shifting of CD4+CD161+ T cells from Th17 to the Th17/Th1 or Th1 phenotype can occur in the SF of children with oligoarticular-onset JIA, and indicate that the accumulation of these cells is correlated with parameters of inflammation. Thus, the results support the hypothesis that these cells may play a role in JIA disease activity. Copyright © 2011 by the American College of Rheumatology.

We have previously shown that human Th17 lymphocytes are characterized by the selective expression of IL-23 receptor (IL-23R), CCR6, CD161, and the transcription factor retinoic acid-related orphan receptor C (RORC), and originate from a CD161(+)CD4(+) naive T-cell precursor in response to the combined activity of IL-1β and IL-23. We show here that not only CD4(+)TCRαβ(+), but also CD8(+)TCRαβ(+), CD4(-)CD8(-) TCRαβ(+), and CD4(-)CD8(-) TCRγδ(+) circulating lymphocytes that produce IL-17 express the distinctive marker CD161 on their surface. In addition, we demonstrate that CD161 expression identifies CD8(+) and CD4(-)CD8(-) umbilical cord blood T cells that already express RORC and IL-23R mRNA and that can be induced to differentiate into IL-17-producing cells in the presence of IL-1β and IL-23. Finally, we provide evidence that umbilical cord blood naive CD4(+)CD161(-) T cells, upon lentivirus-mediated transduction with RORC2 can acquire the ability to express IL-23R, IL-1RI, and CD161, as well as to produce IL-17. Taken together, these data allow to conclude that T-cell subsets able to produce IL-17, as well as precursors of IL-17-producing T cells, exhibit surface expression of CD161, and that this feature is at least in part RORC2-dependent.

Background IL-17A has been suggested to play a pathogenic role in bronchial asthma and other allergic disorders. Objective Study of the relationship between human IL-17A–producing CD4 + T H cells (T H 17) and IL-4–producing CD4 + T H (T H 2) cells. Methods T-cell clones generated from the CCR6 + CD161 + fraction of human circulating CD4 + T cells, which contains virtually all T H 17 cells, as well as circulating CD4 + T cells from both healthy subjects and patients with asthma, were assessed by flow cytometry for their cytokine production profile. Results A small proportion of CCR6 + CD161 + CD4 + T-cell clones showed the ability to produce both IL-17A and IL-4 (T H 17/T H 2). T H 17/T H 2 clones also produced IL-5, IL-8, IL-9, IL-13, IL-21, and IL-22 and displayed the ability to induce the in vitro secretion of IgE. A very few T H 17/T H 2 cells were found among circulating CD4 + T cells from normal subjects, but their proportions were significantly increased in the circulation of patients with chronic asthma. T H 17/T H 2 cells could not be derived from naive umbilical cord blood CD4 + T cells under any experimental condition. However, when circulating memory CCR6 + CD161 + CD4 + T cells were cloned under appropriate polarizing conditions, T H 17/T H 2 clones originated in the presence of IL-4, suggesting that an IL-4–rich microenvironment may induce the shifting of memory T H 17 cells into T H 17/T H 2 cells. Conclusion Because of its peculiar functional properties and the increased numbers in the circulation of patients with bronchial asthma, this previously unknown population of T H 17/T H 2 cells may play some role in the pathogenesis of this disease.

We demonstrate that CD161 is a highly up-regulated gene in human interleukin (IL) 17 T helper cell (Th17) clones and that all IL-17–producing cells are contained in the CD161+ fraction of CD4+ T cells present in the circulation or in inflamed tissues, although they are not CD1-restricted natural killer T cells. More importantly, we show that all IL-17–producing cells originate from CD161+ naive CD4+ T cells of umbilical cord blood, as well as of the postnatal thymus, in response to the combined activity of IL-1β and IL-23. These findings implicate CD161 as a novel surface marker for human Th17 cells and demonstrate the exclusive origin of these cells from a CD161+CD4+ T cell progenitor.

Background CD4 + CD25 + Foxp3 + T-regulatory (Treg) cells play a fundamental role in the control of autoimmunity. Whether human CD4 + CD25 + Foxp3 + Treg cells that recognize foreign antigens also exist is less clear. Objective To investigate the existence in humans of circulating Treg cells able to recognize exogenous antigens, including allergens. Methods CD4 + CD25 high Foxp3 + and CD4 + CD25 - Foxp3 - cells were purified from human peripheral blood and cultured for 15 days with autologous dendritic cells (DCs), unloaded, or loaded with Der p 1 allergen or the bacterial antigen streptokinase (SK). Results CD4 + CD25 high Foxp3 + circulating T cells obtained from healthy nonatopic subjects and cultured with Der p 1–loaded DCs, but not those cultured with either unloaded or SK-loaded DCs, suppressed the proliferative response to Der p 1 of autologous Der p 1–specific T cells generated from the CD4 + CD25 - Foxp3 - subset. The antigen specificity of either Der p 1–CD4 + CD25 high Foxp3 + or SK–CD4 + CD25 high Foxp3 + T cells was confirmed even at clonal level. Finally, under the same experimental conditions, functionally active Der p 1–specific Treg cells were obtained from the pool of circulating CD4 + CD25 high Foxp3 + T cells of Der p 1–sensitive, atopic individuals. Conclusion These data provide undoubted demonstration of the existence of human CD4 + CD25 high Foxp3 + circulating Treg cells specific for exogenous antigens, including the Der p 1 allergen, and indicate that CD4 + CD25 high Foxp3 + Treg cells specific for Der p 1 are present and functionally active in both nonatopic and Der p 1–sensitive, atopic individuals. Clinical implications Caution should be advised in interpreting allergic disorders as simply resulting from defective Treg cell activity.

Background: The identification of mycobacteria represents the gold standard in the diagnosis of tuberculosis (TB), but it is not applicable in all patients, and immunological tests, such as the tuberculin skin test (TST), are not specific and sensitive enough. Methods: By flow cytometry, we measured the CD4 T-cell response to purified protein derivative (PPD) and early secretory antigenic target-6 (ESAT-6) protein using the intracellular cytokine staining technique on whole blood samples obtained from active TB (n = 16), latent TB (n = 17), Bacille Calmette-Guérin (BCG)-vaccinated (n = 11) and healthy (n = 10) donors. All the patients were also tested with conventional TST. Results: The identification by flow cytometry of PPD-specific T lymphocytes upon antigen stimulation of whole blood enables the discrimination of active TB, latent TB and BCG-vaccinated subjects from healthy individuals, whereas the ESAT-6 response discriminated active TB from healthy and BCG-vaccinated individuals. Moreover, this test enables identification of active TB patients who were negative on TST and to distinguish between TB and non-typical mycobacteria TB infections. Conclusions: The identification by flow cytometry of antigen-specific T lymphocytes upon antigen stimulation of whole blood has a better positive predictive value than TST, and could represent a further tool in the diagnosis of TB infection.

Background The mechanisms by which human dendritic cells (DCs) activate a T H 1-polarizing or T H 2-polarizing program are still partially unclear. Objective Study of the mechanisms responsible for the T H 1/T H 2-polarizing activity of human circulating myeloid DCs before and after ligation of their Toll-like receptors (TLRs). Methods IL-4 and IFN-γ production by CD4 + T cells was assessed in cocultures with myeloid DCs before or after TLR triggering. Expression of Jagged-1 and Delta-4 Notch ligands and of GATA-3 and T-box expressed in T cells transcription factors was evaluated by real-time quantitative PCR. Signal transducer and activator of transcription 4 and 6 phosphorylation was assessed by flow cytometry. Knockdown of Jagged-1 or Delta-4 was performed by transfection of DCs with appropriate silencing mRNAs. Results Myeloid immature DCs constitutively expressed Jagged-1, which induces in CD4 + T cells a T H 2 polarization, as shown by Jagged-1 gene silencing. The T H 2 polarization associated with high GATA-3/T-box expressed in T cells ratio and was at least partially dependent on the early induction of IL-4. Maturation of DCs by TLR ligation resulted in the reduction of Jagged-1 and upregulation of Delta-4, which was at least in part responsible for the polarization of CD4 + T cells to the T H 1 phenotype. Conclusion CD4 + T-cell responses are usually characterized by a prevalent T H 2 phenotype unless TLRs are triggered on DCs by microbial components.