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The murine serous cavities contain a rare and enigmatic population of short-lived F4/80 loMHCII + macrophages but what regulates their development, survival, and fate is unclear. Here, we show that mature F4/80 loMHCII + peritoneal macrophages arise after birth, but that this occurs largely independently of colonization by microbiota. Rather, microbiota specifically regulate development of a subpopulation of CD11c + cells that express the immunoregulatory cytokine RELM-α, are reliant on the transcription factor EGR2, and develop independently of the growth factor CSF1. Furthermore, we demonstrate that intrinsic expression of RELM-α, a signature marker shared by CD11c + and CD11c – F4/80 loMHCII + cavity macrophages, regulates survival and differentiation of these cells in the peritoneal cavity in a sex-specific manner. Thus, we identify a previously unappreciated diversity in serous cavity F4/80 loMHCII + macrophages that is regulated by microbiota, and describe a novel sex and site-specific function for RELM-α in regulating macrophage endurance that reveals the unique survival challenge presented to monocyte-derived macrophages by the female peritoneal environment.

The murine serous cavities contain a rare and enigmatic population of short-lived F4/80

The use of bacteria as an alternative cancer therapy has been reinvestigated in recent years. SL7207: an auxotrophic Salmonella enterica serovar Typhimurium aroA mutant with immune-stimulatory potential has proven a promising strain for this purpose. Here, we show that systemic administration of SL7207 induces melanoma tumor growth arrest in vivo, with greater survival of the SL7207-treated group compared to control PBS-treated mice. Administration of SL7207 is accompanied by a change in the immune phenotype of the tumor-infiltrating cells toward pro-inflammatory, with expression of the TH1 cytokines IFN-γ, TNF-α, and IL-12 significantly increased. Interestingly, Ly6C+MHCII+ monocytes were recruited to the tumors following SL7207 treatment and were pro-inflammatory. Accordingly, the abrogation of these infiltrating monocytes using clodronate liposomes prevented SL7207-induced tumor growth inhibition. These data demonstrate a previously unappreciated role for infiltrating inflammatory monocytes underlying bacterial-mediated tumor growth inhibition. This information highlights a possible novel role for monocytes in controlling tumor growth, contributing to our understanding of the immune responses required for successful immunotherapy of cancer.

To understand the contribution of mononuclear phagocytes (MNP), which include monocyte-derived intestinal macrophages, to the pathogenesis of inflammatory bowel disease (IBD), it is necessary to identify functionally-different MNP populations. We aimed to characterise intestinal macrophage populations in patients with IBD. We developed 12-parameter flow cytometry protocols to identify and human intestinal MNPs. We used these protocols to purify and characterize colonic macrophages from colonic tissue from patients with Crohn’s disease (CD), ulcerative colitis (UC), or non-inflamed controls, in a cross-sectional study. We identify macrophage populations (CD45+CD64+ HLA-DR+) and describe two distinct subsets, differentiated by their expression of the mannose receptor, CD206. CD206+ macrophages expressed markers consistent with a mature phenotype: high levels of CD68 and CD163, higher transcription of IL-10 and lower expression of TREM1. CD206− macrophages appear to be less mature, with features more similar to their monocytic precursors. We identified and purified macrophage populations from human colon. These appear to be derived from a monocytic precursor with high CCR2 and low CD206 expression. As these cells mature, they acquire expression of IL-10, CD206, CD63, and CD168. Targeting the newly recruited monocyte-derived cells may represent a fruitful avenue to ameliorate chronic inflammation in IBD.

While immune responses have been rigorously examined after intravenous Listeria monocytogenes (Lm) infection, less is understood about its dissemination from the intestines or the induction of adaptive immunity after more physiologic models of foodborne infection. Consequently, this study focused on early events in the intestinal mucosa and draining mesenteric lymph nodes (MLN) using foodborne infection of mice with Lm modified to invade murine intestinal epithelium (InlAM Lm). InlAM Lm trafficked intracellularly from the intestines to the MLN and were associated with Batf3-independent dendritic cells (DC) in the lymphatics. Consistent with this, InlAM Lm initially disseminated from the gut to the MLN normally in Batf3–/– mice. Activated migratory DC accumulated in the MLN by 3 days post-infection and surrounded foci of InlAM Lm. At this time Batf3–/– mice displayed reduced InlAM Lm burdens, implicating cDC1 in maximal bacterial accumulation in the MLN. Batf3–/– mice also exhibited profound defects in the induction and gut-homing of InlAM Lm-specific effector CD8 T cells. Restoration of pathogen burden did not rescue antigen-specific CD8 T cell responses in Batf3–/– mice, indicating a critical role for Batf3 in generating anti-InlAM Lm immunity following foodborne infection. Collectively, these data suggest that DC play diverse, dynamic roles in the early events following foodborne InlAM Lm infection and in driving the establishment of intestinal Lm-specific effector T cells. Fil: Imperato, Jessica Nancy. Stony Brook University Renaissance School Of Medicine; Estados Unidos Fil: Xu, Daqi. Uconn Health; Estados Unidos Fil: Romagnoli, Pablo Alberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigacion Medica Mercedes y Martin Ferreyra. Grupo Vinculado Centro de Investigacion En Medicina Traslacional Severo R. Amuchastegui - Cimetsa | Universidad Nacional de Cordoba. Instituto de Investigacion Medica Mercedes y Martin Ferreyra. Grupo Vinculado Centro de Investigacion En Medicina Traslacional Severo R. Amuchastegui - Cimetsa | Instituto de Investigacion Medica Mercedes y Martin Ferreyra. Instituto de Investigacion Medica Mercedes y Martin Ferreyra. Grupo Vinculado Centro de Investigacion En Medicina Traslacional Severo R. Amuchastegui - Cimetsa.; Argentina Fil: Qiu, Zhijuan. Stony Brook University Renaissance School Of Medicine; Estados Unidos Fil: Perez, Pedro. Stony Brook University Renaissance School Of Medicine; Estados Unidos Fil: Khairallah, Camille. Stony Brook University Renaissance School Of Medicine; Estados Unidos Fil: Pham, Quynh Mai. Uconn Health; Estados Unidos Fil: Andrusaite, Anna. University of Glasgow; Reino Unido Fil: Bravo Blas, Alberto. The Beatson Institute For Cancer Research; Reino Unido Fil: Milling, Simon W. F.. University of Glasgow; Reino Unido Fil: Lefrancois, Leo. Uconn Health; Estados Unidos Fil: Khanna, Kamal M.. University of New York; Estados Unidos Fil: Puddington, Lynn. Uconn Health; Estados Unidos Fil: Sheridan, Brian S.. Stony Brook University Renaissance School Of Medicine; Estados Unidos

The use of bacteria as an alternative cancer therapy has been re-investigated in recent years. A number of bacterial strains for this purpose have been generated, one of which is SL7207: an auxotrophic Salmonella enterica serovar Typhimurium aroA mutant with immune-stimulatory potential. Here we show that systemic administration of SL7207 induces melanoma tumour growth arrest in vivo, with greater survival of the SL7207-treated group compared to control PBS-treated mice. Administration of SL7207 is accompanied by a change in the immune phenotype of the tumour-infiltrating cells towards pro-inflammatory, with expression of the TH1 cytokines IFN-γ, TNF-α, and IL-12 significantly increased. Interestingly, Ly6C+MHCII+ monocytes were recruited to the tumours following SL7207 treatment and were pro-inflammatory. Accordingly, the abrogation of these infiltrating monocytes using clodronate liposomes prevented SL7207-induced tumour growth inhibition. These data demonstrate a previously unappreciated role for infiltrating inflammatory monocytes underlying bacterial-mediated tumour growth inhibition. This information highlights a novel role for monocytes in controlling tumour growth, contributing to our understanding of the immune responses required for successful immunotherapy of cancer.

Salmonella infection is a globally important cause of gastroenteritis and systemic disease and is a useful tool to study immune responses in the intestine. Although mechanisms leading to immune responses against Salmonella have been extensively studied, questions remain about how bacteria travel from the intestinal mucosa to the mesenteric lymph nodes (MLN), a key site for Ag presentation. In this study, we used a mouse model of infection with Salmonella enterica serovar Typhimurium (STM) to identify changes in intestinal immune cells induced during early infection. We then used fluorescently labeled STM to identify interactions with immune cells from the site of infection through migration in lymph to the MLN. We show that viable STM can be carried in the lymph by any subset of migrating dendritic cells but not by macrophages. Moreover, approximately half of the STM in lymph are not associated with cells at all and travel autonomously. Within the MLN, STM associates with dendritic cells and B cells but predominantly with MLN-resident macrophages. In conclusion, we describe the routes used by STM to spread systemically in the period immediately postinfection. This deeper understanding of the infection process could open new avenues for controlling it.

FoxP3 + regulatory T cells (Tregs) control inflammation and maintain mucosal homeostasis, but their functions during infection are less well understood. Th1, Th2 and Th17 cells can be identified by their master transcription factors (TFs) T-bet, GATA3 and RORγT; Tregs also express these TFs. While T-bet + Tregs can selectively supress Th1 cells, it is unclear whether this is true of Tregs expressing other TFs, or whether such selective suppression can alter the balance of the Th cell response. To address these questions, we used Salmonella enterica serotype Typhimurium (STM) to induce non-lethal colitis. Following infection, we observed an early colonic Th17 response, followed by a Th1-dominated response. The early Th17 response parallels an increase in T-bet + Tregs. Later, Th1 cells and RORγT + Tregs dominate. This reciprocal dynamic between Th cells and Tregs expressing the same TF indicates that Tregs may selectively suppress Th subsets. To test this, Treg depletion experiments were performed. These demonstrated that Tregs enable both the early colonic Th17 response and the later Th1 response. Thus, Tregs can shape the tissue CD4 T cell response in a fine-tuned manner. This highlights the potential for subpopulations of Tregs to be used in targeted therapeutic approaches.

Macrophages in the healthy intestine are highly specialized and usually respond to the gut microbiota without provoking an inflammatory response. A breakdown in this tolerance leads to inflammatory bowel disease (IBD), but the mechanisms by which intestinal macrophages normally become conditioned to promote microbial tolerance are unclear. Strong epidemiological evidence linking disruption of the gut microbiota by antibiotic use early in life to IBD indicates an important role for the gut microbiota in modulating intestinal immunity. Here, we show that antibiotic use causes intestinal macrophages to become hyperresponsive to bacterial stimulation, producing excess inflammatory cytokines. Re-exposure of antibiotic-treated mice to conventional microbiota induced a long-term, macrophage-dependent increase in inflammatory T helper 1 (TH1) responses in the colon and sustained dysbiosis. The consequences of this dysregulated macrophage activity for T cell function were demonstrated by increased susceptibility to infections requiring TH17 and TH2 responses for clearance (bacterial Citrobacter rodentium and helminth Trichuris muris infections), corresponding with increased inflammation. Short-chain fatty acids (SCFAs) were depleted during antibiotic administration; supplementation of antibiotics with the SCFA butyrate restored the characteristic hyporesponsiveness of intestinal macrophages and prevented T cell dysfunction. Butyrate altered the metabolic behavior of macrophages to increase oxidative phosphorylation and also promoted alternative macrophage activation. In summary, the gut microbiota is essential to maintain macrophage-dependent intestinal immune homeostasis, mediated by SCFA-dependent pathways. Oral antibiotics disrupt this process to promote sustained T cell-mediated dysfunction and increased susceptibility to infections, highlighting important implications of repeated broad-spectrum antibiotic use.

Purpose of review The microorganisms that colonise our bodies, the commensal 'microbiota', respond to changes in our behaviour and environment, and can also profoundly affect our health. We can now investigate these organisms with unprecedented depth and precision, revealing that they may contribute to the pathogenesis of diseases including arthritis. Here we discuss the changes occurring in the microbiota in people with arthritis, and how manipulation of the microbiota may provide an additional pathway for therapy. Recent findings We highlight two important aspects of the recent literature. First we describe changes in the microbiota identified in people with arthritis; these correlations give insights into the microbial changes that may contribute to symptoms of arthritis. We then discuss attempts to ameliorate arthritis by manipulating the microbiota. This is a rapidly developing area of research. There are tantalising hints that interventions targeting the microbiota may become therapeutically viable for some types of inflammatory arthritis. Summary Our commensal microbial communities respond to changes in our health, and are altered in people with arthritis. Understanding the complex relationships between the microbiota and the body may enable us to deliberately manipulate these organisms and provide additional therapeutic options for people with arthritis.

International audience; The paradigm that macrophages that reside in steady-state tissues are derived from embryonic precursors has never been investigated in the intestine, which contains the largest pool of macrophages. Using fate-mapping models and monocytopenic mice, together with bone marrow chimera and parabiotic models, we found that embryonic precursor cells seeded the intestinal mucosa and demonstrated extensive in situ proliferation during the neonatal period. However, these cells did not persist in the intestine of adult mice. Instead, they were replaced around the time of weaning by the chemokine receptor CCR2-dependent influx of Ly6C(hi) monocytes that differentiated locally into mature, anti-inflammatory macrophages. This process was driven largely by the microbiota and had to be continued throughout adult life to maintain a normal intestinal macrophage pool.

Avian influenza is a disease of paramount economical importance for the poultry industry. In Mexico, only low pathogenicity H5N2 strain has been reported and it is controlled through inactivated-virus inoculation. This emulsified vaccine reduces clinical signs indeed, but not viral shedding. Over the last 50 years Transfer Factor (TF) has shown to be an efficient immunomodulator and has been used successfully in human clinical cases, and less commonly in animal models. The aim of this work was to establish an avian influenza-specific TF dose able to produce the highest percentage of mRNA expression of the following cytokines: IL-2 and IFN-γ. An experiment to show the mRNA expression of these cytokines in chicken previously inoculated with avian influenza-specific TF was set up. In the first experiment 0.1, 1 and 10 TF units were inoculated into 3 different groups of chickens; PCR for cytokines from splenic tissue was performed. For the second experiment, a second TF inoculation in combination with the vaccine was carried out using 3 new groups of chicken. Experiment 1: Only IL-2 expression was achieved in 58.33% of chickens using 1 TF unit (P < 0.05). In experiment 2, 75% of chickens showed IL-2 with 1 TF unit (P < 0.05) and all of them (100%) expressed IFN-γ(P < 0.01). From these results it can be concluded that IFN-γand IL-2 expression can be induced by the inoculation of 1 TF unit (equivalent to 7.3μg of protein) at the beginning of the experiment procedure and after a second inoculation of TF (10 days after) together with the inactivated virus vaccine. &nbsp, La influenza aviar es una enfermedad de gran importancia económica para la industria avícola. En México sólo se ha reportado la cepa H5N2 de baja patogenicidad y ésta se controla mediante la vacunación con virus inactivado. Esta vacuna en emulsión reduce la presencia de signos, pero no la eliminación viral. Desde hace más de 50 años se ha informado acerca de la eficacia del Factor de Transferencia (FT) como inmunomodulador en casos clínicos humanos y en menor cantidad en modelos animales. El objetivo de este trabajo fue el de establecer la dosis que produce un mayor porcentaje de expresión del RNAm de dos citocinas: IL-2 y de IFN-γ. Se diseñó un experimento para evidenciar la expresión del RNAm de estas dos citocinas en pollos previamente inoculados con FT específico para influenza aviar. En la primera fase se aplicaron 0,1, 1, y 10 unidades de FT a diferentes grupos de pollos, posteriormente se realizó la PCR a partir de tejido esplénico. En la segunda fase se aplicó el FT junto con la vacuna a tres nuevos grupos de pollos. Del experimento 1 solamente IL-2 tuvo un porcentaje mayor de positivos (58,33%) con 1 unidad (P < 0,05). En cambio, en el experimento 2, con 1 unidad se obtuvo 75% de positivos para IL-2 (P < 0,05) y 100% para IFN-γ(P < 0,01). De estos resultados su puede concluir que al aplicar una unidad de FT (equivalente a 7,3μg de proteína) al inicio del experimento y 10 días después otra unidad de FT junto con la vacuna inactivada de IA se indujo la expresión del RNAm de IFN-γe IL-2. &nbsp

La influenza aviar es una enfermedad de gran importancia economica para la industria avicola. En Mexico solo se ha reportado la cepa H5N2 de baja patogenicidad y esta se controla mediante la vacunacion con virus inactivado. Esta vacuna en emulsion reduce la presencia de signos, pero no la eliminacion viral. Desde hace mas de 50 anos se ha informado acerca de la eficacia del Factor de Transferencia (FT) como inmunomodulador en casos clinicos humanos y en menor cantidad en modelos animales. El objetivo de este trabajo fue el de establecer la dosis que produce un mayor porcentaje de expresion del RNAm de dos citocinas: IL-2 y de IFN- γ . Se diseno un experimento para evidenciar la expresion del RNAm de estas dos citocinas en pollos previamente inoculados con FT especifico para influenza aviar. En la primera fase se aplicaron 0,1, 1, y 10 unidades de FT a diferentes grupos de pollos, posteriormente se realizo la PCR a partir de tejido esplenico. En la segunda fase se aplico el FT junto con la vacuna a tres nuevos grupos de pollos. Del experimento 1 solamente IL-2 tuvo un porcentaje mayor de positivos (58,33%) con 1 unidad (P < 0,05). En cambio, en el experimento 2, con 1 unidad se obtuvo 75% de positivos para IL-2 (P < 0,05) y 100% para IFN- γ (P < 0,01). De estos resultados su puede concluir que al aplicar una unidad de FT (equivalente a 7,3 μg de proteina) al inicio del experimento y 10 dias despues otra unidad de FT junto con la vacuna inactivada de IA se indujo la expresion del RNAm de IFN- γ e IL-2

Nat. Immunol. doi:10.1038/ni.2967 corrected online 8 September 2014 In the version of this article initially published online, the vertical axis of the bottom right graph in Figure 3h was incorrect. It should read “F4/80loCD11b+ cells (×105).” Also, in the Online Methods, the first sentence of the third subsection (“Generation of bone marrow chimeras”) identifies the donor mice incorrectly.