In vivo studies fail to reveal a role for IL-4 or STAT6 signaling in Th2 lymphocyte differentiation

The expression of interleukin-4 (IL-4) is viewed as the hallmark of a Th2 lymphocyte, whereas the subsequent action of IL-4 and IL-13, mediated through the STAT6 signaling pathway, is seen as a prerequisite for the full development of Th2 immune responses to parasites and allergens. G4 mice, whose IL-4 gene locus contains the fluorescent reporter eGFP, were used to quantify the number of Th2 cells that develop during Nippostrongylus brasiliensis- or allergen-induced immune responses under conditions where IL-4 or STAT6 was absent. Here, we show that deletion of IL-4 or STAT6 had little impact on the number or timing of appearance of IL-4-producing Th2 cells. These data indicate that in vivo differentiation of naïve CD4 T cells to Th2 status often occurs independently of IL-4 and STAT6 and that recently described pathways of Th2 cell differentiation may explain how allergens and parasites selectively induce Th2-mediated immunity.     

不同临床类型的HBV感染者外周血T淋巴细胞STAT信号表达的研究

目的研究不同临床类型HBV感染者外周血T细胞表达细胞因子水平与细胞因子受体信号蛋白（STATs）活性间的关系。方法检测慢性乙肝（CHB）、慢性重型肝炎（CSH）、健康携带者（AsC）以及健康者T细胞表达IFN-γ、IL-12、IL-10、IL-4含量及细胞内STAT-1、3、4、5、6活性。结果 CHB、CSH及AsC细胞因子水平普遍上升（P〈0.001或0.01）。IL-10、IL-12受体信号STAT3和STAT4活性与细胞因子水平一致;IFN-γ、IL-4受体信号STAT1、STAT6活性与细胞因子水平不一致,不同个体间差异较大。结论不同临床类型的HBV感染者T细胞表达Th1型和Th2型细胞因子普遍增强,细胞内STATs活性与细胞因子含量不完全一致,细胞内STATs活性存在个体差距。     

TLR agonists induce regulatory dendritic cells to recruit Th1 cells via preferential IP-10 secretion and inhibit Th1 proliferation

Dendritic cells (DCs) and chemokines are important mediators linking innate and adaptive immunity on activation by Toll-like receptor (TLR) agonists. We previously identified a kind of regulatory DC subset (diffDCs) that differentiated from mature DCs under splenic stroma and that inhibited T-cell proliferation. The responsiveness of such regulatory DCs to TLR agonists and their pattern of chemokine production remain to be determined. Here, we report that the regulatory DCs secrete a higher level of CXCR3 chemokine IFN-gamma-induced protein-10 (IP-10) than immature DCs (imDCs), and more IP-10 is produced after stimulation with TLR-2, -4, -3, and -9 ligands. Blockade of IFN-alpha/beta inhibits IP-10 production by TLR agonist-activated regulatory DCs. We show that the increased IRF-3 and IFN-beta-induced STAT1 activation are responsible for the autocrine IFN-beta-dependent preferential production of IP-10 by regulatory DCs. In addition, stimulation with recombinant mouse IFN-alpha/beta induces more IP-10 production in regulatory DCs than that in imDCs. Moreover, the regulatory DCs selectively recruit more Th1 cells through IP-10 and inhibit Th1 proliferation. Our results demonstrate a new manner for regulatory DCs to down-regulate T-cell response by preferential IP-10 production and inhibition of recruited Th1 cell proliferation.     

Experimental Leishmania major infection in mice: role of IL-10

L. major infection of mice induces polarized Th1 and Th2 responses that are correlated with healing of the infection (Th1) or a fatal disease (Th2). The Th subset specific cytokines, IFNgamma and IL-4, themselves were shown to be important factors for the differentiation into the Th1 and Th2 pathways during infection. We studied the role of the Th2 cytokine IL-10 during leishmania infection: removal of endogenous IL-10 by anti-IL-10 treatment did not alter the Th2 cytokine pattern in non-healer mice nor did it modulate DTH reactivity, IgE production or fatal disease progression, but partially blocked the IFNgamma inhibiting effect of rIL-4 in healer mice. During chronic infection similar amounts of IL-10 were produced in both healer and non-healer mice. However, at early time-points during infection IL-10 production was significantly higher in the non-healer Th2 responder animals. IL-10 production in vitro caused significant inhibition of in vitro IFNgamma production. In conclusion IL-10, unlike IL-4 and IFNgamma, does not seem to play a readily detectable role in the Th subset differentiation during L. major infection. However, the high production of IL-10 early during infection in non-healer mice and inhibition of leishmania-specific IFNgamma production may contribute to drive the immune response towards a Th2 response.     

Interleukin-21 enhances T-helper cell type I signaling and interferon-gamma production in Crohn's disease

BACKGROUND & AIMS: T-helper (Th)1 cells play a central role in the pathogenesis of tissue damage in Crohn's disease (CD). Interleukin (IL)-12/STAT4 signaling promotes Th1 cell commitment in CD, but other cytokines are needed to maintain activated Th1 cells in the mucosa. In this study, we examined the expression and role of IL-21, a T-cell-derived cytokine of the IL-2 family; in tissues and cells isolated from patients with inflammatory bowel disease. METHODS: IL-21 was examined by Western blotting in whole mucosa and lamina propria mononuclear cells (LPMCs) from patients with CD, ulcerative colitis (UC), and controls. We also examined the effects of exogenous IL-12 on IL-21 production, as well as the effects of blocking IL-21 with an IL-21-receptor Ig fusion protein. Interferon (IFN)-gamma was measured in the culture supernatants by enzyme-linked immunosorbent assay, and phosphorylated STAT4 and T-bet were examined by Western blotting. RESULTS: IL-21 was detected in all samples, but its expression was higher at the site of disease in CD in comparison with UC and controls. Enhanced IL-21 was seen in both ileal and colonic CD and in fibrostenosing and nonfibrostenosing disease. IL-12 enhanced IL-21 in normal lamina propria lymphocytes through an IFN-gamma-independent mechanism, and blocking IL-12 in CD LPMCs decreased anti-CD3-stimulated IL-21 expression. Neutralization of IL-21 in CD LPMC cultures decreased phosphorylated STAT4 and T-bet expression, thereby inhibiting IFN-gamma production. CONCLUSIONS: Our data suggest that IL-21 contributes to the ongoing Th1 mucosal response in CD.     

Suppressive oligodeoxynucleotides inhibit atherosclerosis in ApoE(-/-) mice through modulation of Th1/Th2 balance

Atherosclerosis is a chronic inflammatory disease, which is positively and negatively regulated by T helper (Th) 1 and Th2 lymphocytes, respectively. Recent findings indicate that suppressive oligodeoxynucleotides (ODNs) expressing TTAGGG motifs selectively reduce Th1 cytokine production and have been proven effective at blocking the development of organ-specific autoimmune diseases. In the current research, we hypothesized that suppressive ODNs may alter the development of atherosclerosis. Eight-week-old homozygous ApoE^−/− male mice were injected with 300 μg ODNs A151 (TTAGGG) or nonspecific ODNs 1612. Atherosclerotic lesion sizes were dramatically reduced by ODNs A151, but not by nonspecific ODNs. MCP-1 and VCAM-1, which are the key inflammatory factors in atherogenesis, were significantly attenuated by the suppressive ODNs A151. In the splenic lymphocytes, FACS analysis showed ODNs A151 reduced the percentage of IFN-γ-producing Th1 cells and slightly increased the percentage of IL-4-producing Th2 cells, indicating that suppressive ODNs skewed the Th1/Th2 balance toward Th2 inflammation in vivo. Furthermore, ODNs A151 down-regulated the phosphorylation of STAT1 and STAT4 and suppressed up-regulation of T-bet, a signal modulator for Th1, and didn't impact GATA-3 and STAT6, which are associated with a Th2 phenotype. Consistent with this in vivo observation, ELISA analysis demonstrated that ODNs A151 suppressed Th1 cytokines IFN-γ and TNF-α, and augmented Th2 cytokines IL-4 and IL-10 in vitro. This study provides the first experimental evidence that suppressive ODNs inhibit the development of atherosclerosis through inhibition of the STAT1/4 and T-bet pathways, which further modulate the Th1/Th2 balance in vivo.     

Type 1/Type 2 immunity in infectious diseases.

T helper type 1 (Th1) lymphocytes secrete secrete interleukin (IL)-2, interferon-gamma, and lymphotoxin-alpha and stimulate type 1 immunity, which is characterized by intense phagocytic activity. Conversely, Th2 cells secrete IL-4, IL-5, IL-9, IL-10, and IL-13 and stimulate type 2 immunity, which is characterized by high antibody titers. Type 1 and type 2 immunity are not strictly synonymous with cell-mediated and humoral immunity, because Th1 cells also stimulate moderate levels of antibody production, whereas Th2 cells actively suppress phagocytosis. For most infections, save those caused by large eukaryotic pathogens, type 1 immunity is protective, whereas type 2 responses assist with the resolution of cell-mediated inflammation. Severe systemic stress, immunosuppression, or overwhelming microbial inoculation causes the immune system to mount a type 2 response to an infection normally controlled by type 1 immunity. In such cases, administration of antimicrobial chemotherapy and exogenous cytokines restores systemic balance, which allows successful immune responses to clear the infection.     

IL-1 family members and STAT activators induce cytokine production by Th2, Th17, and Th1 cells

Expression of T1ST2, the IL-33R, by Th2 cells requires GATA3. Resting Th2 cells express little GATA3, which is increased by IL-33 and a STAT5 activator, in turn increasing T1ST2 from its low-level expression on resting Th2 cells. Th2 cells that have upregulated T1ST2 produce IL-13, but not IL-4, in response to IL-33 plus a STAT5 activator in an antigen-independent, NF-κB-dependent, cyclosporin A (CsA)-resistant manner. Similarly, Th17 cells produce IL-17A in response to IL-1β and a STAT3 activator and Th1 cells produce IFNγ in response to IL-18 and a STAT4 inducer. Thus, each effector Th cell produces cytokines without antigenic stimulation in response to an IL-1 family member and a specific STAT activator, implying an innate mechanism through which memory CD4 T cells are recruited by an induced cytokine environment.