Lisa A. Mielke

General Nature of the STAT3-Activated Anti-Inflammatory Response

Although many cytokine receptors generate their signals via the STAT3 pathway, the IL-10R appears unique in promoting a potent anti-inflammatory response (AIR) via STAT3 to antagonize proinflammatory signals that activate the innate immune response. We found that heterologous cytokine receptor systems that activate STAT3 but are naturally refractory (the IL-22R), or engineered to be refractory (the IL-6, leptin, and erythropoietin receptors), to suppressor of cytokine signaling-3-mediated inhibition activate an AIR indistinguishable from IL-10. We conclude that the AIR is a generic cytokine signaling pathway dependent on STAT3 but not unique to the IL-10R.

IL-17-producing γδ T cells and innate lymphoid cells

The inflammatory cytokine IL‐17 plays a critical role in immunity to infection and is involved in the inflammatory pathology associated with certain autoimmune diseases, such as psoriasis and rheumatoid arthritis. While CD4+ and CD8+ T cells are important sources of this cytokine, recent evidence has suggested that γδ T cells and a number of families of innate lymphoid cells (ILCs) can secrete IL‐17 and related cytokines. The production of IL‐17 by γδ T cells appears to be largely independent of T‐cell receptor act‐ivation and is promoted through cytokine signalling, in particular by IL‐23 in combination with IL‐1β or IL‐18. Therefore IL‐17‐secreting γδ T cells can be categorised as a family of cells similar to innate‐like lymphoid cells. IL‐17‐secreting γδ T cells function as a part of mucosal defence against infection, with most studies to date focusing on their response to bacterial pathogens. γδ T cells also play a pathological role in certain autoimmune diseases, where they provide an early source of IL‐17 and IL‐21, which initiate responses mediated by conventional IL‐17‐secreting CD4+ T cells (Th17 cells). ILCs lack an antigen receptor or other linage markers, and ILC subsets that express the transcriptional factor RORγt have been found to secrete IL‐17. Evidence is emerging that these newly recognised sources of IL‐17 play both pathological and protective roles in inflammatory diseases as discussed in this article.

T-box Transcription Factors Combine with the Cytokines TGF-β and IL-15 to Control Tissue-Resident Memory T Cell Fate

Tissue-resident memory T (Trm) cells contribute to local immune protection in non-lymphoid tissues such as skin and mucosa, but little is known about their transcriptional regulation. Here we showed that CD8(+)CD103(+) Trm cells, independent of circulating memory Txa0cells, were sufficient for protection against infection and described molecular elements that were crucial for their development in skin and lung. We demonstrated that the T-box transcription factors (TFs) Eomes and T-bet combined to control CD8(+)CD103(+) Trm cell formation, such that their coordinate downregulation was crucial for TGF-β cytokine signaling. TGF-β signaling, in turn, resulted in reciprocal T-box TF downregulation. However, whereas extinguishment of Eomes was necessary for CD8(+)CD103(+) Trm cell development, residual T-bet expression maintained cell surface interleukin-15 (IL-15) receptor β-chain (CD122) expression and thus IL-15 responsiveness. These findings indicate that the T-box TFs control the two cytokines, TGF-β and IL-15, which are pivotal for CD8(+)CD103(+) Trm cell development and survival.

TCF-1 Controls ILC2 and NKp46+RORγt+ Innate Lymphocyte Differentiation and Protection in Intestinal Inflammation

Innate lymphocyte populations play a central role in conferring protective immunity at the mucosal frontier. In this study, we demonstrate that T cell factor 1 (TCF-1; encoded by Tcf7), a transcription factor also important for NK and T cell differentiation, is expressed by multiple innate lymphoid cell (ILC) subsets, including GATA3+ nuocytes (ILC2) and NKp46+ ILCs (ILC3), which confer protection against lung and intestinal inflammation. TCF-1 was intrinsically required for the differentiation of both ILC2 and NKp46+ ILC3. Loss of TCF-1 expression impaired the capacity of these ILC subsets to produce IL-5, IL-13, and IL-22 and resulted in crippled responses to intestinal infection with Citrobacter rodentium. Furthermore, a reduction in T-bet expression required for Notch-2–dependent development of NKp46+ ILC3 showed a dose-dependent reduction in TCF-1 expression. Collectively, our findings demonstrate an essential requirement for TCF-1 in ILC2 differentiation and reveal a link among Tcf7, Notch, and Tbx21 in NKp46+ ILC3 development.

Socs3 maintains the specificity of biological responses to cytokine signals during granulocyte and macrophage differentiation

Granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) play key roles in regulating emergency granulopoiesis and inflammation, and are both negatively regulated by the inducible intracellular protein suppressor of cytokine signaling-3 (Socs3). Mice with Socs3 deleted specifically in hematopoietic cells succumb to severe neutrophil and macrophage-driven inflammation by 1 year of age, and responses to G-CSF are grossly exacerbated. In order to determine which elements of cellular responses to cytokines require Socs3, we have examined the differentiative and proliferative capacity of hematopoietic progenitor cells stimulated by G-CSF and IL-6. The differentiation of Socs3-deficient progenitor cells is skewed toward macrophage production in response to G-CSF or IL-6, whereas wild-type progenitor cells produce mainly neutrophils. The proliferative capacity of Socs3-deficient progenitor cells is greatly enhanced in response to G-CSF at all concentrations, but only at low concentrations for IL-6. Strikingly, synergistic responses to costimulation with stem cell factor and IL-6 (but not G-CSF) are lost at higher concentrations in Socs3-deficient progenitor cells. Cytokine-induced expression of transcriptional regulators including cebpb, Ets2, Bcl3, c-Myc, Jun, and Fosl2 are differentially regulated in Socs3-deficient cells. The tight regulation by Socs3 of signal transducer and activator of transcription 3 phosphorylation and gene transcription after cytokine receptor ligation significantly influences the fate of myeloid progenitor cells.

Abstract 1443: IL-18 is associated with the onset and progression of gastric cancer

INTRODUCTION: Gastric cancer (GC) is the fourth most prevalent, and the third most common cause of cancer-related death worldwide. The disease is generally asymptomatic, and consequently is often diagnosed at an advanced stage when metastasis is present, and limited treatment options are available. Chronic inflammation is recognized as an integral component in the development and progression of GC, and is associated with increased infiltration of immune cells into the tumor microenvironment. The production of pro-inflammatory cytokines by these cells may contribute to tumor progression through activation of pathways promoting tumor cell survival and proliferation. Previous work from our lab has shown that therapeutic inhibition of the inflammatory cytokine interleukin (IL)-11 is effective in ameliorating disease progression in gastrointestinal cancer, however, it is unclear what role other pro-inflammatory cytokines, such as IL-18, might have in disease progression. METHODS: To characterize the role of different pro-inflammatory cytokines in GC, we first analyzed microarray and qRT-PCR data of from human GC specimens and adjacent non-tumor tissue. Following the generation of a candidate list of cytokines deregulated in human GC, the role of individual cytokines in disease progression was examined using a validated mouse model of intestinal-type GC, referred to as gp130Y757F, by crossing into cytokine knock-out strains and monitoring tumor burden and the expression of genes and proteins classically associated with tumorigenesis. RESULTS: We found that the expression pro-inflammatory cytokines including IL-1β and IL-18 were significantly elevated in the tumors of human GC patients compared to non-tumor tissue. In gp130Y757F mice, genetic ablation of IL-18, but not of IL-1β significantly reduced gastric tumor burden, which was associated with a reduction in the number of intratumoral macrophages, but not lymphocytes. This observation correlated with decreased expression of pro-inflammatory (Ifng, Tgfb1), antimicrobial (Reg3b, Reg3g), and tissue remodeling (Mmp9) genes, and a reduction in apoptosis in the gastric lesions in these mice. CONCLUSION: Our results demonstrate that IL-18 has an important role in GC disease progression, and may serve as a potential therapeutic target. Citation Format: Paul Nguyen, Rita Busuttil, Lisa Mielke, Gabrielle Belz, Alex Boussioutas, Matthias Ernst, Tracy Putoczki. IL-18 is associated with the onset and progression of gastric cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1443.