Distinctive pattern of cytokine production and adhesion molecule expression in peripheral blood memory CD4+ T cells from patients with active Crohn's disease

[The characterization analysis of pathogenic T cells in immune-mediated aplastic anemia mouse model]

Objective: This study aims, in addition to characterizing pathogenic T cells trafficking to bone marrow (BM) and other organs, to establish immune-mediated AA C.B10 mouse model by DsRed mouse (B6 background) lymph nodes (LN) cells infusion after a total body irradiation (TBI) . Methods: The C.B10 mice received a 5 Gy TBI and then were infused with DsRed mouse (B6 background) LN cells at 5×10(6)/mouse via a tail vein injection. The severity of bone marrow failure (BMF) was observed by mononuclear cell count in bone marrow and peripheral blood cell count. On days 3, 6, 9, and 12, mice were sacrificed and collected BM, spleens, LN, or thymus to analyze the dynamic change and activation status of donor T cells in these organs by a flow cytometry. At day 12, the donor-derived T cells from BM, spleens, and LN were sorted to collect the DsRed(+)CD3(+)CD4(+) T cells and DsRed(+)CD3(+)CD8(+) T cells for RNA isolation and gene expression analyses by PCR array. Results: Relative to control animals that received 5 Gy TBI without LN cell infusion, AA mice developed severe BMF with dramatic decrease in total BM cells, hemoglobin, white blood cells, and platelets in peripheral blood on days 9 and 12 after the LN cell infusion. The frequencies of DsRed(+) T cells trafficking to BM, LN, and spleens increased with time. Surprisingly, although the DsRed(+) T cells in BM increased dramatically at a level much higher than those in the spleens and LN on day 12, there were very few DsRed(+) T cells in BM on days three and six, which was significantly lower than those in spleens or LN. The frequency of DsRed(+) T cells in thymus was the lowest during the whole process. On day 12, the DsRed(+)CD3(+)CD4(+) T cells of BM, LN, and spleens from AA mice were (91.38±2.10) %, (39.78±6.98) %, and (67.87±12.77) %, respectively. On the contrary, the DsRed(+)CD3(+)CD8(+)T cells of BM, LN, and spleens were (98.21±1.49) %, (94.06±4.20) %, and (96.29±1.23) %, respectively. We assessed the donor T cell phenotypes using the CD44 and CD62L markers and found that almost all of the DsRed(+)CD4(+) or DsRed(+)CD8(+) T cells in BM were effector memory T cell phenotype from day 9 to day 12. Meanwhile, transcriptome analyses showed higher expression in CD38, IFN-γ, LAG3, CSF1, SPP1, and TNFSF13B in BM DsRed(+)CD4(+) and DsRed(+)CD8(+) T cells. However, there was a lower expression in FOXP3 and CTLA4 in BM DsRed(+)CD4(+) T cells than those in spleens and LN. Conclusions: The DsRed LN cells infusion to induce BMF in CB10 mice enabled to track the donor-derived pathogenic T cells. Besides previously published findings in this model, we demonstrated that donor CD4(+) and CD8(+) T cells primarily homed to spleens and LN, expanded and differentiated, then infiltrated in BM with a terminal effector memory phenotype. The T cells infiltrated in BM showed more activation and less immunosuppression characteristics compared to those homing to spleens and LN during the BMF development.

Mesenchymal Stem Cells Improve Rheumatoid Arthritis Progression by Controlling Memory T Cell Response

In the last years, mesenchymal stem cell (MSC)-based therapies have become an interesting therapeutic opportunity for the treatment of rheumatoid arthritis (RA) due to their capacity to potently modulate the immune response. RA is a chronic autoimmune inflammatory disorder with an incompletely understood etiology. However, it has been well described that peripheral tolerance defects and the subsequent abnormal infiltration and activation of diverse immune cells into the synovial membrane, are critical for RA development and progression. Moreover, the imbalance between the immune response of pro-inflammatory and anti-inflammatory cells, in particular between memory Th17 and memory regulatory T cells (Treg), respectively, is well admitted to be associated to RA immunopathogenesis. In this context, MSCs, which are able to alter the frequency and function of memory lymphocytes including Th17, follicular helper T (Tfh) cells and gamma delta (γδ) T cells while promoting Treg cell generation, have been proposed as a candidate of choice for RA cell therapy. Indeed, given the plasticity of memory CD4⁺ T cells, it is reasonable to think that MSCs will restore the balance between pro-inflammatory and anti-inflammatory memory T cells populations deregulated in RA leading to prompt their therapeutic function. In the present review, we will discuss the role of memory T cells implicated in RA pathogenesis and the beneficial effects exerted by MSCs on the phenotype and functions of these immune cells abnormally regulated in RA and how this regulation could impact RA progression.

Mechanisms of T cell organotropism

Protective immunity relies upon T cell differentiation and subsequent migration to target tissues. Similarly, immune homeostasis requires the localization of regulatory T cells (Tregs) to the sites where immunity takes place. While naïve T lymphocytes recirculate predominantly in secondary lymphoid tissue, primed T cells and activated Tregs must traffic to the antigen rich non-lymphoid tissue to exert effector and regulatory responses, respectively. Following priming in draining lymph nodes, T cells acquire the 'homing receptors' to facilitate their access to specific tissues and organs. An additional level of topographic specificity is provided by T cells receptor recognition of antigen displayed by the endothelium. Furthermore, co-stimulatory signals (such as those induced by CD28) have been shown not only to regulate T cell activation and differentiation, but also to orchestrate the anatomy of the ensuing T cell response. We here review the molecular mechanisms supporting trafficking of both effector and regulatory T cells to specific antigen-rich tissues.

Interleukin-19 impairment in active Crohn's disease patients

The exact function of interleukin-19 (IL-19) on immune response is poorly understood. In mice, IL-19 up-regulates TNFα and IL-6 expression and its deficiency increases susceptibility to DSS-induced colitis. In humans, IL-19 favors a Th2 response and is elevated in several diseases. We here investigate the expression and effects of IL-19 on cells from active Crohn’s disease (CD) patient. Twenty-three active CD patients and 20 healthy controls (HC) were included. mRNA and protein IL-19 levels were analyzed in monocytes. IL-19 effects were determined in vitro on the T cell phenotype and in the production of cytokines by immune cells. We observed that unstimulated and TLR-activated monocytes expressed significantly lower IL-19 mRNA in active CD patients than in HC (logFC = −1.97 unstimulated; −1.88 with Pam3CSK4; and −1.91 with FSL-1; p<0.001). These results were confirmed at protein level. Exogenous IL-19 had an anti-inflammatory effect on HC but not on CD patients. IL-19 decreased TNFα production in PBMC (850.7±75.29 pg/ml vs 2626.0±350 pg/ml; p<0.01) and increased CTLA4 expression (22.04±1.55% vs 13.98±2.05%; p<0.05) and IL-4 production (32.5±8.9 pg/ml vs 13.5±2.9 pg/ml; p<0.05) in T cells from HC. IL-10 regulated IL-19 production in both active CD patients and HC. We observed that three of the miRNAs that can modulate IL-19 mRNA expression, were up-regulated in monocytes from active CD patients. These results suggested that IL-19 had an anti-inflammatory role in this study. Defects in IL-19 expression and the lack of response to this cytokine could contribute to inflammatory mechanisms in active CD patients.

Increased prevalence of circulating novel IL-17 secreting Foxp3 expressing CD4+ T cells and defective suppressive function of circulating Foxp3+ regulatory cells support plasticity between Th17 and regulatory T cells in inflammatory bowel disease patients

BACKGROUND

IL-17 and Foxp3 double-expressing (DE) CD4(+) T lymphocytes are novel crossover immune cell population, but the presence and role of these cells in human intestinal inflammation is unclear. The aim of this study was to investigate the circulating IL-17 and Foxp3 DE CD4(+) T lymphocytes in patients with inflammatory bowel disease (IBD).

METHODS

The entire cohort consisted of 79 subjects: 31 patients with Crohn's disease, 28 patients with ulcerative colitis, and 20 healthy control subjects (HC). IBD patients with evidence of active disease at endoscopy were entered into the study. Peripheral blood mononuclear cells were used for ex vivo and in vitro studies to assess the characteristics and generation of these novel cells and the function of circulating Foxp3 CD4(+) regulatory T lymphocytes (Treg) in patients with IBD compared with HC.

RESULTS

Patients with IBD had significantly higher prevalence of IL-17 and Foxp3 DE CD4(+) T lymphocytes compared with age- and gender-matched HC. These cells expressed RORγt. The ability of Treg cells to suppress autologous T-cell proliferation was reduced by approximately 60% in patients with IBD compared with HC. Increased generation of these DE cells was demonstrated by the modulation of cytokine environment of CD4(+) lymphocytes in vitro in patients with Crohn's disease.

CONCLUSIONS

Prevalence of circulating IL-17 and Foxp3 DE CD4(+) T cells is increased in patients with IBD. Coexpression of RORγt and Foxp3 in these cells implies conversion from Treg cells to Th17 cells. This is associated with a decreased suppressive function of Foxp3 CD4(+) T lymphocytes in patients with IBD.

Cytokine profiles in peripheral blood of children and adults with Crohn disease

BACKGROUND

Increasing evidence suggests that cytokine dysregulation in T-helper 1 and T-helper 2 (TH1/TH2) subsets contributes to the pathogenesis of Crohn disease (CD). The present pilot study examines the hypothesis that cytokine profiles differ between pediatric and adult patients with CD.

METHODS

Production of TH1 cytokines interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) and of TH2 cytokines interleukin-4 (IL-4) and IL-6 was analyzed in peripheral blood of patients with CD and healthy controls (n=20) using flow cytometry after in vitro stimulation.

RESULTS

In both pediatric and adult subjects, frequencies of TNF-α CD4+ T cells were higher in patients with CD than in controls (P=0.009 and P=0.047, respectively). Percentages of cells expressing IL-4 were slightly increased (P=0.036), whereas those for IFN-γ were decreased (P=0.009) in pediatric patients with CD compared with controls. As expected, the overall production of TH1 cytokines was higher in adults compared with pediatric subjects. When memory CD4+CD45RO+ T cells were considered, lower IFN-γ expression was observed in pediatric subjects with CD compared with controls (P=0.009), matching the trend seen in the general CD4+ T cell population. The percentage of CD4+CD45RO+ T cells was increased in adult patients with CD compared with pediatric patients with CD (P=0.016).

CONCLUSIONS

The present study describes a peripheral blood TH1/TH2 cytokine imbalance in CD and suggests different immunological mechanisms in children and adults for disease pathogenesis.

T-cell autoreactivity to citrullinated autoantigenic peptides in rheumatoid arthritis patients carrying HLA-DRB1 shared epitope alleles

Introduction

Anti-citrullinated peptide antibodies are found in rheumatoid arthritis (RA) patients with HLA-DRβ chains encoding the shared epitope (SE) sequence. Citrullination increases self-antigen immunogenicity, through increased binding affinity to SE-containing HLA-DR molecules. To characterise T-cell autoreactivity towards citrullinated self-epitopes, we profiled responses of SE⁺ healthy controls and RA patients to citrullinated and unmodified epitopes of four autoantigens.

Methods

We compared T-cell proliferative and cytokine responses to citrullinated and native type II collagen 1,237 to 1,249, vimentin 66 to 78, aggrecan 84 to 103 and fibrinogen 79 to 91 in six SE⁺ healthy controls and in 21 RA patients with varying disease duration. Cytokine-producing cells were stained after incubation with peptide in the presence of Brefeldin-A.

Results

Although proliferative responses were low, IL-6, IL-17 and TNF were secreted by CD4⁺ T cells of SE⁺ RA patients and healthy controls, as well as IFNγ and IL-10 secreted by RA patients, in response to citrullinated peptides. Of the epitopes tested, citrullinated aggrecan was most immunogenic. Patients with early RA were more likely to produce IL-6 in response to no epitope or to citrullinated aggrecan, while patients with longstanding RA were more likely to produce IL-6 to more than one epitope. Cytokine-producing CD4⁺ T cells included the CD45RO⁺ and CD45RO^- and the CD28⁺ and CD28^- subsets in RA patients.

Conclusion

Proinflammatory cytokines were produced by CD4⁺ T cells in SE⁺ individuals in response to citrullinated self-epitopes, of which citrullinated aggrecan was most immunogenic. Our data suggest that the T-cell response to citrullinated self-epitopes matures and diversifies with development of RA.

Molecular mechanism of interleukin-2-induced mucosal homeostasis

Sustained damage to the mucosal lining in patients with inflammatory bowel disease (IBD) facilitates translocation of intestinal microbes to submucosal immune cells leading to chronic inflammation. Previously, we demonstrated the role of Jak3 in IL-2-induced intestinal epithelial cell (IEC) migration, one of the early events during intestinal wound repair. In this study, we demonstrate that IL-2 also plays a role in IEC homeostasis through concentration-dependent regulation of IEC proliferation and cell death. At lower concentrations (≤50 U/ml), IL-2 promoted proliferation, while at higher concentrations (100 U/ml), it promoted apoptosis. Activation by IL-2 led to tyrosine phosphorylation-dependent interactions between Jak3 and p52ShcA only at lower concentrations. Phosphatase SHP1 dephosphorylated IL-2-induced phosphorylated p52ShcA. Higher concentrations of IL-2 decreased the phosphorylation of Jak3 and p52ShcA, disrupted their interactions, redistributed Jak3 to the nucleus, and induced apoptosis in IEC. IL-2 also induced dose-dependent upregulation of p52shcA and downregulation of jak3-mRNA. Constitutive overexpression and mir-shRNA-mediated knockdown studies showed that expression of both Jak3 and p52ShcA were necessary for IL-2-induced proliferation of IEC. Doxycycline-regulated sh-RNA expression demonstrated that IL-2-induced downregulation of jak3-mRNA was responsible for higher IL-2-induced apoptosis in IEC. Collectively, these data demonstrate a novel mechanism of IL-2-induced mucosal homeostasis through posttranslational and transcriptional regulation of Jak3 and p52ShcA.

Monocytes differentiated with GM-CSF and IL-15 initiate Th17 and Th1 responses that are contact-dependent and mediated by IL-15

Distinct types of DCs are generated from monocytes using GM-CSF with IL-4 (IL4-DC) or IL-15 (IL15-DC). IL15-DCs are potent inducers of antigen-specific CD8(+) T cells, display a phenotype similar to CD14(+) cells commonly described in chronically inflamed tissues, and produce high levels of IL-1β and IL-15 in response to TLR4 stimulation. As these cytokines promote Th17 responses, which are also associated with inflammatory diseases, I hypothesized that TLR-primed IL15-DCs favor Th17 activation over IL4-DCs. Compared with IL4-DCs, IL15-DCs stimulated with TLR agonists secreted significantly higher concentrations of the Th17-promoting factors, IL-1β, IL-6, IL-23, and CCL20, and lower levels of the Th1 cytokine, IL-12. In addition, IL15-DCs and not IL4-DCs up-regulated IL-15 on the cell surface in response to TLR agonists. IL15-DCs primed with TLR3 or TLR4 agonists triggered Th17 (IL-17, IL-22, and/or IFN-γ) and Th1 (IFN-γ) responses, whereas IL4-DCs primed with the same TLR agonists activated Th1 (IFN-γ) responses. Secretion of IL-17 and IFN-γ required contact with TLR-primed IL15-DC, and IFN-γ production was mediated by membrane-bound IL-15. These findings identify key differences in monocyte-derived DCs, which impact adaptive immunity, and provide primary evidence that IL-15 promotes Th17 and Th1 responses by skewing monocytes into IL15-DC.

CD44v7 ligation downregulates the inflammatory immune response in Crohn's disease patients by apoptosis induction in mononuclear cells from the lamina propria

Deletion of exon CD44v7 abrogates experimental colitis by apoptosis induction in intestinal mononuclear cells. Here we show that CD44v7 expression was upregulated upon CD40 ligation in human mononuclear cells, and examined whether ligation of CD44v7 also affects activation and apoptosis in lamina propria mononuclear cells (LPMC) from Crohn's disease (CD) patients. Thirty five patients with chronic inflammatory bowel disease (IBD), fourteen controls and four patients with diverticulitis were evaluated. CD44v7 was upregulated predominantly in the inflamed mucosa of CD patients. Furthermore, incubation with an anti-CD44v7 antibody induced apoptosis in LPMC isolated from inflamed mucosa of CD patients, but not from non-inflamed mucosa, from patients with ulcerative colitis (UC) or from normal controls. CD40 ligation and simultaneous incubation with anti-CD44v7 significantly downregulated CD80 in dendritic cells, thus inhibiting a critical second signal for naive T-cell activation. The apoptotic signal was mediated via the intrinsic mitochondrial pathway with decreased Bcl-2 and increased 7A6 (a mitochondrial membrane protein) expression. It was Fas independent and required caspases-3 and -9 activation. The process is highly specific for macrophage activation via CD40. These findings point to a novel mechanism of apoptosis induction in CD patients mediated by CD44v7 ligation.