Identification of two migratory colon ILC2 populations differentially expressing IL-17A and IL-5/IL-13

Group 2 innate lymphoid cells(ILC2s)play important tissue resident roles in anti-parasite immunity,allergic immune response,tissue homeostasis,and tumor immunity.ILC2s are considered tissue resident cells with little proliferation at steady state.Recent studies have shown that a subset of small intestinal ILC2s could leave their residing tissues,circulate and migrate to different organs,including lung,liver,mesenteric LN and spleen,upon activation.However,it remains unknown whether other ILC populations with migratory behavior exist.In this study,we find two major colon ILC2 populations with potential to migrate to the lung in response to IL-25 stimulation.One subset expresses IL-17A and resembles inflammatory ILC2s(iILC2s)but lacks CD27 expression,whereas the other expresses CD27 but not IL-17A.In addition,the IL-17A^(+)ILC2s express lower levels of CD127,CD25,and ST2 than CD27^(+)ILC2s,which express higher levels of IL-5 and IL-13.Surprisingly,we found that both colon ILC2 populations still maintained their colonic features of preferential expression of IL-17A and CD27,IL-5/IL-13,respectively.Together,our study identifies two migratory colon ILC2 subsets with unique surface markers and cytokine profiles which are critical in regulating lung and colon immunity and homeostasis.

A novel reporter mouse line for studying alveolar macrophages

Alveolar macrophages(AMs)are self-maintained immune cells that play vital roles in lung homeostasis and immunity.Although reporter mice and culture systems have been established for studying macrophages,an accurate and specific reporter line for alveolar macrophage study is still not available.Here we reported a novel Rspo1-tdTomato gene reporter mouse line that could specifically label mouse AMs in a cell-intrinsic manner.Using this reporter system,we visualized the dynamics of alveolar macrophages intravitally under steady state and characterized the alveolar macrophage differentiation under in vitro condition.By performing ATAC-seq,we found that insertion of the tdTomato cassette in the Rspo1 locus increased the accessibility of a PPARE motif within the Rspo1 locus and revealed a potential regulation by key transcription factor PPAR-γfor alveolar macrophage differentiation in vitro and in vivo.Consistently,perturbation of PPAR-γby its agonist rosiglitazone or inhibitor GW9662 resulted in corresponding alteration of tdTomato expression in alveolar macrophages together with the transcription of PPAR-γdownstream target genes.Furthermore,global transcriptomic analyses of AMs from the wild type mice and the Rspo1-tdTomato mice showed comparable gene expression profiles,especially those AM-specific genes,confirming that the insertion of the tdTomato cassette in the Rspo1 locus does not impact the cell identity and biological function of AMs under normal condition.Taken together,our study provides an alternative tool for in vivo and in vitro labeling of alveolar macrophages with high specificity which could also be utilized as an indicator of PPAR-γactivity for future development of PPAR-γspecific targeting drugs.

Regulation of CD8^(+)T memory and exhaustion by the mTOR signals

CD8^(+)T cells are the key executioners of the adaptive immune arm,which mediates antitumor and antiviral immunity.Naïve CD8^(+)T cells develop in the thymus and are quickly activated in the periphery after encountering a cognate antigen,which induces these cells to proliferate and differentiate into effector cells that fight the initial infection.Simultaneously,a fraction of these cells become long-lived memory CD8^(+)T cells that combat future infections.Notably,the generation and maintenance of memory cells is profoundly affected by various in vivo conditions,such as the mode of primary activation(e.g.,acute vs.chronic immunization)or fluctuations in host metabolic,inflammatory,or aging factors.Therefore,many T cells may be lost or become exhausted and no longer functional.Complicated intracellular signaling pathways,transcription factors,epigenetic modifications,and metabolic processes are involved in this process.Therefore,understanding the cellular and molecular basis for the generation and fate of memory and exhausted CD8^(+)cells is central for harnessing cellular immunity.In this review,we focus on mammalian target of rapamycin(mTOR),particularly signaling mediated by mTOR complex(mTORC)2 in memory and exhausted CD8^(+)T cells at the molecular level.

Author Correction:Regulation of CD8^(+)T memory and exhaustion by the mTOR signals

Correction to:Cellular&Molecular Immunology https://doi.org/10.1038/s41423-023-01064-3,published online 15 August 2023 In this article the author name Yuheng Han was incorrectly written as Yuhen Han.The original article has been corrected.

Metabolic regulation of T cell development by Sinl-mTORC2 is mediated by pyruvate kinase M2

Glucose metabolism plays a key role in thymocyte development. The mammalian target of rapamycin complex 2 (mT0RC2) is a critical regulator of cell growth and metabolism, but its role in early thymocyte development and metabolism has not been fully studied. We show here that genetic ablation of Sinl, an essential component of mTORC2, in T lineage cells results in severely impaired thymocyte development at the CD4^- CD8^- double negative (DN) stages but not at the CD4^+ CD8^+ double positive (DP) or later stages. Notably, Sinl-deficient DN thymocytes show markedly reduced proliferation and glycolysis.Importantly, we discover that the M2 isoform of pyruvate kinase (PKM2) is a novel and crucial Sinl effector in promoting DN thymocyte development and metabolism. At the molecular level, we show that Sinl-mTORC2 controls PKM2 expression through an AKT-dependent PPAR-y nuclear translocation. Together, our study unravels a novel mTORC2-PPAR-γ-PKM2 pathway in immune-metabolic regulation of early thymocyte development.

MAP3K2 augments Th1 cell differentiation via IL-18 to promote T cell-mediated colitis

T cell-mediated immunity in the intestine is stringently controlled to ensure proper immunity against pathogenic microbes and to prevent autoimmunity,a known cause of inflammatory bowel disease.However,precisely how T cells regulate intestine immunity remains to be fully understood.In this study,we found that mitogen-activated protein kinase kinase kinase 2(MAP3K2)is required for the CD4^(+)T cell-mediated inflammation in the intestine.Using a T cell transfer colitis model,we found that MAP3K2-deficient naïve CD4^(+)T cells had a dramatically reduced ability to induce colitis compared to wild type T cells.In addition,significantly fewer IFN-γ-but more IL-17A-producing CD4^(+)T cells in the intestines of mice receiving MAP3K2-deficient T cells than in those from mice receiving wild type T cells was observed.Interestingly,under well-defined in vitro differentiation conditions,MAP3K2-deficient naïve T cells were not impaired in their ability to differentiate into Th1,Th17 and Treg.Furthermore,the MAP3K2-regulated colitis severity was mediated by Th1 but not Th17 cells in the intestine.At the molecular level,we showed that MAP3K2-mediated Th1 cell differentiation in the intestine was regulated by IL-18 and required specific JNK activation.Together,our study reveals a novel regulatory role of MAP3K2 in intestinal T cell immunity via the IL-18-MAP3K2-JNK axis and may provide a novel target for intervention in T cell-mediated colitis.

Comments on‘MAP3K2-regulated intestinal stromal cells define a distinct stem cell niche’

For a long period of time,intestinal mesenchymal stromal cells(IMSC)have been considered as a relatively simple and homogeneous group of cells.These cells could effectively regulate intestinal homeostasis and epithelium integrity via producing growth factors and cytokines(Powell et al.,2011).With the help of single-cell transcriptomics studies,it has now been clear that IMSC are quite complex and heterogeneous(Kinchen et al.,2018).

scRNA-seq profiling of neonatal and adult thymus-derived CD4+ T cells by a T cell origin-time tracing model

It is well documented that the neonatal thymus-derived (neonatal-TD) regulatory T cells (Treg) are essential to prevent lethal autoimmune diseases and allergies, and neonatal and adult thymus possesses distinct output potentials for naïve T cells, including Treg. However, the molecular features and detailed functional differences between neonatal-TD and adult thymus-derived (adult-TD) T cells in terms of their ability to maintain immune homeostasis during long-term environmental influences are still largely unknown, partially due to the lack of appropriate animal models to precisely trace these cells at specific time points. In this study, neonatal-TD and adult-TD CD4+ T cells from the spleen and Peyer's patches were traced for 9 weeks by a T cell origin-time tracing mouse model and analysed by single-cell RNA sequencing. More Treg but fewer naïve T cells were found in neonatal-TD CD4+ T cells from both tissues than those from adult-TD counterparts. Interestingly, the neonatal-TD Treg in both the spleen and Peyer's patches exhibited augmented expression of Foxp3, Gata3, Ctla4, Icos, Il2ra, Tgfb1, and Nrp1, as well as enriched Gene Ontology terms like T cell activation and tolerance induction, indicating an enhanced immunosuppressive function. These results were further confirmed by flow cytometry analysis and in vitro immune suppression assays. Flow cytometry also revealed a significantly higher proportion of neonatal-TD Treg in total Treg than that of adult-TD counterparts, suggesting the longer lifespan of neonatal-TD Treg. To investigate the intrinsic features of neonatal-TD and adult-TD CD4+ T cells, a shortened tracing time was performed. Surprisingly, the neonatal-TD and adult-TD CD4+ T cells had similar proportions of Treg and did not exhibit significant differences in Foxp3, Gata3, Ctla4, Icos, Il2ra, and Tgfb1 expression levels after tracing for 12 days. On the other hand, neonatal-TD Treg present an increased Nrp1 expression level compared with adult-TD counterparts, indicating the enhanced stability. Together, our work reveals that the neonatal-TD Treg are more immunosuppressive, which is likely shaped primarily by environmental factors.