Parasite-induced TH1 cells and intestinal dysbiosis cooperate in IFN-γ-dependent elimination of Paneth cells.

Activation of Toll-like receptors (TLRs) by pathogens triggers cytokine production and T cell activation, immune defense mechanisms that are linked to immunopathology. Here we show that IFN-γ production by CD4(+) T(H)1 cells during mucosal responses to the protozoan parasite Toxoplasma gondii resulted in dysbiosis and the elimination of Paneth cells. Paneth cell death led to loss of antimicrobial peptides and occurred in conjunction with uncontrolled expansion of the Enterobacteriaceae family of Gram-negative bacteria. The expanded intestinal bacteria were required for the parasite-induced intestinal pathology. The investigation of cell type-specific factors regulating T(H)1 polarization during T. gondii infection identified the T cell-intrinsic TLR pathway as a major regulator of IFN-γ production in CD4(+) T cells responsible for Paneth cell death, dysbiosis and intestinal immunopathology.

Exosomes facilitate intercellular communication between uterine perivascular adipose tissue and vascular smooth muscle cells in pregnant rats.

Perivascular adipose tissue (PVAT) is distinct from other adipose depots, as it has differential gene and protein profiles and vasoactive functions. We have shown that pregnancy affects the morphology of PVAT surrounding the uterine arteries (utPVAT) differentially than the morphology of nonperivascular reproductive adipose depots (i.e., periovarian adipose tissue, OVAT). Here, we hypothesized that pregnancy modifies the profile (size and molecular mass) of exosome-like extracellular vesicles released by utPVAT (Exo-utPVAT) compared with exosome-like extracellular vesicles released by OVAT (Exo-OVAT) and that primary uterine vascular smooth muscle cells (utVSMCs) can internalize Exo-utPVAT. Our findings indicate that utPVAT from pregnant and nonpregnant rats secrete exosome-like vesicles. Exo-utPVAT from pregnant rats were smaller (i.e., molecular size) and heavier (i.e., molecular mass) than those from nonpregnant rats, whereas pregnancy did not affect the size of Exo-OVAT. Immunocytochemistry and confocal microscopy showed that primary utVSMCs internalized Exo-utPVAT (both tissues from the same pregnant rat) labeled by the lipophilic tracer DiO. Treatment of isolated uterine arteries with Exo-utPVAT did not affect relaxation responses to acetylcholine in pregnant or nonpregnant rats. Collectively, these findings demonstrate a novel type of intercellular communication between Exo-utPVAT and utVSMCs and indicate pregnancy modulates the morphology and cargo of Exo-utPVAT.NEW & NOTEWORTHY Uterine perivascular adipose tissue secretes exosome-like vesicles, which are internalized by their adjacent uterine vascular smooth muscle cells. Consideration of the exosomal communication between adipose tissue and vascular smooth muscle cells in the uterine circulation in mathematical models and experimental designs may help us to improve understanding of mechanisms underlying uterine artery adaptive responses to a healthy pregnancy and during pregnancy complications.

Cutting Edge: Developmental Regulation of IFN-γ Production by Mouse Neutrophil Precursor Cells.

Neutrophils are an emerging cellular source of IFN-γ, a key cytokine that mediates host defense to intracellular pathogens. Production of IFN-γ by neutrophils, in contrast to lymphoid cells, is TLR- and IL-12-independent and the events associated with IFN-γ production by neutrophils are not understood. In this study, we show that mouse neutrophils express IFN-γ during their lineage development in the bone marrow niche at the promyelocyte stage independently of microbes. IFN-γ accumulates in primary neutrophilic granules and is released upon induction of degranulation. The developmental mechanism of IFN-γ production in neutrophils arms the innate immune cells prior to infection and assures the potential for rapid release of IFN-γ upon neutrophil activation, the first step during responses to many microbial infections.

TLR-independent neutrophil-derived IFN-γ is important for host resistance to intracellular pathogens.

IFN-γ is a major cytokine that is critical for host resistance to a broad range of intracellular pathogens. Production of IFN-γ by natural killer and T cells is initiated by the recognition of pathogens by Toll-like receptors (TLRs). In an experimental model of toxoplasmosis, we have identified the presence of a nonlymphoid source of IFN-γ that was particularly evident in the absence of TLR-mediated recognition of Toxoplasma gondii. Genetically altered mice lacking all lymphoid cells due to deficiencies in Recombination Activating Gene 2 and IL-2Rγc genes also produced IFN-γ in response to the protozoan parasite. Flow-cytometry and morphological examinations of non-NK/non-T IFN-γ(+) cells identified neutrophils as the cell type capable of producing IFN-γ. Selective elimination of neutrophils in TLR11(-/-) mice infected with the parasite resulted in acute susceptibility similar to that observed in IFN-γ-deficient mice. Similarly, Salmonella typhimurium infection of TLR-deficient mice induces the appearance of IFN-γ(+) neutrophils. Thus, neutrophils are a crucial source for IFN-γ that is required for TLR-independent host protection against intracellular pathogens.

Copper metabolism domain-containing 1 represses genes that promote inflammation and protects mice from colitis and colitis-associated cancer.

BACKGROUND & AIMS: Activation of the transcription factor nuclear factor-κB (NF-κB) has been associated with the development of inflammatory bowel disease (IBD). Copper metabolism MURR1 domain containing 1 (COMMD1), a regulator of various transport pathways, has been shown to limit NF-κB activation. We investigated the roles of COMMD1 in the pathogenesis of colitis in mice and IBD in human beings. METHODS: We created mice with a specific disruption of Commd1 in myeloid cells (Mye-knockout [K/O] mice); we analyzed immune cell populations and functions and expression of genes regulated by NF-κB. Sepsis was induced in Mye-K/O and wild-type mice by cecal ligation and puncture or intraperitoneal injection of lipopolysaccharide (LPS), colitis was induced by administration of dextran sodium sulfate, and colitis-associated cancer was induced by administration of dextran sodium sulfate and azoxymethane. We measured levels of COMMD1 messenger RNA in colon biopsy specimens from 29 patients with IBD and 16 patients without (controls), and validated findings in an independent cohort (17 patients with IBD and 22 controls). We searched for polymorphisms in or near COMMD1 that were associated with IBD using data from the International IBD Genetics Consortium and performed quantitative trait locus analysis. RESULTS: In comparing gene expression patterns between myeloid cells from Mye-K/O and wild-type mice, we found that COMMD1 represses expression of genes induced by LPS. Mye-K/O mice had more intense inflammatory responses to LPS and developed more severe sepsis and colitis, with greater mortality. More Mye-K/O mice with colitis developed colon dysplasia and tumors than wild-type mice. We observed a reduced expression of COMMD1 in colon biopsy specimens and circulating leukocytes from patients with IBD. We associated single-nucleotide variants near COMMD1 with reduced expression of the gene and linked them with increased risk for ulcerative colitis. CONCLUSIONS: Expression of COMMD1 by myeloid cells has anti-inflammatory effects. Reduced expression or function of COMMD1 could be involved in the pathogenesis of IBD.

Cooperation of TLR12 and TLR11 in the IRF8-dependent IL-12 response to Toxoplasma gondii profilin.

TLRs play a central role in the innate recognition of pathogens and the activation of dendritic cells (DCs). In this study, we establish that, in addition to TLR11, TLR12 recognizes the profilin protein of the protozoan parasite Toxoplasma gondii and regulates IL-12 production by DCs in response to the parasite. Similar to TLR11, TLR12 is an endolysosomal innate immune receptor that colocalizes and interacts with UNC93B1. Biochemical experiments revealed that TLR11 and TLR12 directly bind to T. gondii profilin and are capable of forming a heterodimer complex. We also establish that the transcription factor IFN regulatory factor 8, not NF-κB, plays a central role in the regulation of the TLR11- and TLR12-dependent IL-12 response of DCs. These results suggest a central role for IFN regulatory factor 8-expressing CD8(+) DCs in governing the TLR11- and TLR12-mediated host defense against T. gondii.

Maternal high-fat diet results in microbiota-dependent expansion of ILC3s in mice offspring.

Maternal obesity and a high-fat diet (HFD) during the perinatal period have documented short- and long-term adverse outcomes for offspring. However, the mechanisms of maternal HFD effects on neonatal offspring are unclear. While the effects of maternal HFD exposure during pregnancy on the offspring are increasingly being appreciated, we do not know if maternal HFD alters the microbiota or affects neonatal susceptibility to inflammatory conditions, nor the mechanisms involved. In this study, we show that the offspring of mothers exposed to HFD develop a unique microbiota, marked by expansion of Firmicutes, and an increase in IL-17-producing type 3 innate lymphoid cells (ILC3s). The expansion of ILC3s was recapitulated through neocolonization with HFD microbiota alone. Further, the HFD offspring were susceptible to a neonatal model of inflammation that was reversible with IL-17 blockade. Collectively, these data suggest a previously unknown and unique role for ILC3s in the promotion of an early inflammatory susceptibility in the offspring of mothers exposed to HFD.

Proteobacteria-specific IgA regulates maturation of the intestinal microbiota.

The intestinal microbiota changes dynamically from birth to adulthood. In this study we identified γ-Proteobacteria as a dominant phylum present in newborn mice that is suppressed in normal adult microbiota. The transition from a neonatal to a mature microbiota was in part regulated by induction of a γ-Proteobacteria-specific IgA response. Neocolonization experiments in germ-free mice further revealed a dominant Proteobacteria-specific IgA response triggered by the immature microbiota. Finally, a role for B cells in the regulation of microbiota maturation was confirmed in IgA-deficient mice. Mice lacking IgA had persistent intestinal colonization with γ-Proteobacteria that resulted in sustained intestinal inflammation and increased susceptibility to neonatal and adult models of intestinal injury. Collectively, these results identify an IgA-dependent mechanism responsible for the maturation of the intestinal microbiota.