Interleukin-17B Antagonizes Interleukin-25-Mediated Mucosal Inflammation.

The interleukin-17 (IL-17) family of cytokines has emerged as a critical player in inflammatory diseases. Among them, IL-25 has been shown to be important in allergic inflammation and protection against parasitic infection. Here we have demonstrated that IL-17B, a poorly understood cytokine, functions to inhibit IL-25-driven inflammation. IL-17B and IL-25, both binding to the interleukin-17 receptor B (IL-17RB), were upregulated in their expression after acute colonic inflammation. Individual inhibition of these cytokines revealed opposing functions in colon inflammation: IL-25 was pathogenic but IL-17B was protective. Similarly opposing phenotypes were observed in Citrobacter rodentium infection and allergic asthma. Moreover, IL-25 was found to promote IL-6 production from colon epithelial cells, which was inhibited by IL-17B. Therefore, our data demonstrate that IL-17B is an anti-inflammatory cytokine in the IL-17 family.

MAPK phosphatase 7 regulates T cell differentiation via inhibiting ERK-mediated IL-2 expression.

Members of the MAPK phosphatase (MKP) protein family play critical roles in immune responses through differential regulation of MAPK activation. In this study, we show that MKP7, also known as dual-specificity phosphatase 16, was required for CD4(+) T cell responses in vivo. Mkp7(-/-) CD4(+) T cells exhibited enhanced ERK and JNK activation, and produced increased amount of IL-2 compared with Mkp7(+/+) cells upon activation. Mkp7(-/-) CD4(+) T cells were selectively defective in Th17 differentiation in vitro, which was rescued by blocking IL-2 or inhibition of ERK activation. Furthermore, mice carrying Mkp7(-/-) T cells were deficient in generation of Th17 and T follicular helper cells in vivo, and were resistant to autoimmune experimental encephalomyelitis. Our results thus demonstrate an essential role of MKP7 in effector T cell function.

The signal transducers STAT5 and STAT3 control expression of Id2 and E2-2 during dendritic cell development.

Cytokines and transcription factors play key roles in dendritic cell (DC) development, yet information about regulatory interactions between these signals remains limited. Here we show that the cytokines GM-CSF and Flt3L induce the transcriptional mediators Id2 and E2-2 and control DC lineage diversification by STAT-dependent pathways. We found that STAT5 is required for tissue CD103(+) DC generation and plasmacytoid DC (pDC) suppression in steady state or response to GM-CSF. STAT5 stimulates GM-CSF-dependent expression of Id2, which controls CD103(+) DC production and pDC inhibition. By contrast, pDCs, but not CD103(+) DCs, are dependent on STAT3. Consistently, STAT3 stimulates Flt3L-responsive expression of the pDC regulator Tcf4 (E2-2). These data suggest that STATs contribute to DC development by controlling transcription factors involved in lineage differentiation.

Cutting edge: regulation of intestinal inflammation and barrier function by IL-17C.

In the IL-17 family of cytokines, much is known about the sources and functions of IL-17, IL-17F, and IL-25 in the host defense against infection and in inflammatory diseases; however, the physiological function of IL-17C remains poorly understood. Using mice deficient in IL-17C, we demonstrate that this cytokine is crucial for the regulation of an acute experimental colitis elicited by dextran sulfate sodium. In this model, mice lacking IL-17C exhibited exacerbated disease that was associated with increased IL-17 expression by γδ T cells and Th17 cells. Moreover, IL-17C directly regulated the expression of the tight junction molecule occludin by colonic epithelial cells. Thus, our data suggest that IL-17C plays a critical role in maintaining mucosal barrier integrity.

Dual A2A/ A2B adenosine receptor antagonist M1069 counteracts immuno-suppressive mechanisms of adenosine and reduces tumor growth in vivo.

While A2A adenosine receptor (AR) was considered as a major contributor to adenosine-mediated immunosuppression, A2B, having the lowest affinity to adenosine, has also emerged as a potential contributor to tumor promotion. Therefore, in adenosine-rich tumor microenvironment (TME), where A2B could be complementary and/or compensatory to A2A, simultaneous targeting of A2A and A2B ARs can provide higher potential for cancer immunotherapy. We developed M1069 - a highly selective dual antagonist of the A2A and A2B AR. In assays with primary human and murine immune cells, M1069 rescued IL 2 production from T cells (A2A dependent) and inhibited VEGF production by myeloid cells (A2B dependent) in adenosine-high settings. M1069 also demonstrated superior suppression of secretion of pro tumorigenic cytokines CXCL1, CXCL5, and rescue of IL 12 secretion from adenosine differentiated dendritic cells compared to an A2A selective antagonist (A2Ai). In a one-way mixed lymphocyte reaction (MLR) assay, adenosine differentiated human and murine dendritic cells treated with M1069 demonstrated superior T cell stimulatory activity compared to dendritic cells differentiated in presence of A2Ai. In vivo, M1069 decreased tumor growth as a monotherapy and enhanced anti-tumor activity of bintrafusp alfa (BA) or cisplatin in syngeneic adenosinehi/CD73hi 4T1 breast tumor model, but not in the CD73 knockout (KO) 4T1 tumor model or in adenosinelow/CD73low MC38 murine colon carcinoma model. In summary, our dual A2A/A2B AR antagonist M1069 may counteract immune-suppressive mechanisms of high concentrations of adenosine in vitro and in vivo and enhance the anti-tumor activity of other agents, including BA and cisplatin.

Genome-wide Analysis Identifies Bcl6-Controlled Regulatory Networks during T Follicular Helper Cell Differentiation.

T follicular helper (Tfh) cell is a unique T cell subset specialized in promoting humoral immunity. B-cell lymphoma 6 protein (Bcl6) has been identified as an obligatory transcription factor in Tfh cells; however, the molecular mechanism underlying Bcl6 function remains largely unknown. Here, we defined Bcl6 target genes in Tfh cells by analyzing genome-wide Bcl6 occupancy together with transcriptome profiling. With consensus sequences being different from those in Th9, B cells, and macrophages, Bcl6 binding in Tfh cell was closely associated with a decrease in 5-hydroxymethylcytosine (5hmC). Importantly, Bcl6 promoted Tfh cell differentiation through antagonizing IL-7R (CD127)/signal transducer and activator of transcription (STAT) 5 axis; deletion of the Bcl6 gene in T cells resulted in enhanced IL-7R-STAT5 signaling and substantial expansion of CD127(hi) non-Tfh cells. Thus, our study systemically examines Bcl6-controlled regulatory networks and provides important insights into Bcl6's biological functions in Tfh cells.

Evasion of IFN-γ signaling by Francisella novicida is dependent upon Francisella outer membrane protein C.

BACKGROUND: Francisella tularensis is a Gram-negative facultative intracellular bacterium and the causative agent of the lethal disease tularemia. An outer membrane protein (FTT0918) of F. tularensis subsp. tularensis has been identified as a virulence factor. We generated a F. novicida (F. tularensis subsp. novicida) FTN_0444 (homolog of FTT0918) fopC mutant to study the virulence-associated mechanism(s) of FTT0918. METHODS AND FINDINGS: The ΔfopC strain phenotype was characterized using immunological and biochemical assays. Attenuated virulence via the pulmonary route in wildtype C57BL/6 and BALB/c mice, as well as in knockout (KO) mice, including MHC I, MHC II, and µmT (B cell deficient), but not in IFN-γ or IFN-γR KO mice was observed. Primary bone marrow derived macrophages (BMDM) prepared from C57BL/6 mice treated with rIFN-γ exhibited greater inhibition of intracellular ΔfopC than wildtype U112 strain replication; whereas, IFN-γR KO macrophages showed no IFN-γ-dependent inhibition of ΔfopC replication. Moreover, phosphorylation of STAT1 was downregulated by the wildtype strain, but not the fopC mutant, in rIFN-γ treated macrophages. Addition of NG-monomethyl-L-arginine, an NOS inhibitor, led to an increase of ΔfopC replication to that seen in the BMDM unstimulated with rIFN-γ. Enzymatic screening of ΔfopC revealed aberrant acid phosphatase activity and localization. Furthermore, a greater abundance of different proteins in the culture supernatants of ΔfopC than that in the wildtype U112 strain was observed. CONCLUSIONS: F. novicida FopC protein facilitates evasion of IFN-γ-mediated immune defense(s) by down-regulation of STAT1 phosphorylation and nitric oxide production, thereby promoting virulence. Additionally, the FopC protein also may play a role in maintaining outer membrane stability (integrity) facilitating the activity and localization of acid phosphatases and other F. novicida cell components.