Peyer's patch phagocytes acquire specific transcriptional programs that influence their maturation and activation profiles

Peyer's patches (PPs) are secondary lymphoid organs in contact with the external environment via the intestinal lumen, thus combining antigen sampling and immune response initiation sites. Therefore, they provide a unique opportunity to study the entire process of phagocyte differentiation and activation in vivo. Here, we deciphered the transcriptional and spatial landscape of PP phagocyte populations from their emergence in the tissue to their final maturation state at homeostasis and under stimulation. Activation of monocyte-derived Lysozyme-expressing dendritic cells (LysoDCs) differs from that of macrophages by their upregulation of conventional DC (cDC) signature genes such as Ccr7 and downregulation of typical monocyte-derived cell genes such as Cx3cr1. We identified gene sets that distinguish PP cDCs from the villus ones and from LysoDCs. We also identified key immature, early, intermediate, and late maturation markers of PP phagocytes. Finally, exploiting the ability of the PP interfollicular region to host both villous and subepithelial dome emigrated cDCs, we showed that the type of stimulus, the subset, but also the initial location of cDCs shape their activation profile and thus direct the immune response. Our study highlights the importance of targeting the right phagocyte subset at the right place and time to manipulate the immune response.

Intragranuloma Accumulation and Inflammatory Differentiation of Neutrophils Underlie Mycobacterial ESX-1-Dependent Immunopathology

The conserved ESX-1 type VII secretion system is a major virulence determinant of pathogenic mycobacteria, including Mycobacterium tuberculosis and Mycobacterium marinum. ESX-1 is known to interact with infected macrophages, but its potential roles in regulating other host cells and immunopathology have remained largely unexplored. Using a murine M. marinum infection model, we identify neutrophils and Ly6C⁺MHCII⁺ monocytes as the main cellular reservoirs for the bacteria. We show that ESX-1 promotes intragranuloma accumulation of neutrophils and that neutrophils have a previously unrecognized required role in executing ESX-1-mediated pathology. To explore if ESX-1 also regulates the function of recruited neutrophils, we performed a single-cell RNA-sequencing analysis that indicated that ESX-1 drives newly recruited uninfected neutrophils into an inflammatory phenotype via an extrinsic mechanism. In contrast, monocytes restricted the accumulation of neutrophils and immunopathology, demonstrating a major host-protective function for monocytes specifically by suppressing ESX-1-dependent neutrophilic inflammation. Inducible nitric oxide synthase (iNOS) activity was required for the suppressive mechanism, and we identified Ly6C⁺MHCII⁺ monocytes as the main iNOS-expressing cell type in the infected tissue. These results suggest that ESX-1 mediates immunopathology by promoting neutrophil accumulation and phenotypic differentiation in the infected tissue, and they demonstrate an antagonistic interplay between monocytes and neutrophils by which monocytes suppress host-detrimental neutrophilic inflammation. IMPORTANCE The ESX-1 type VII secretion system is required for virulence of pathogenic mycobacteria, including Mycobacterium tuberculosis. ESX-1 interacts with infected macrophages, but its potential roles in regulating other host cells and immunopathology have remained largely unexplored. We demonstrate that ESX-1 promotes immunopathology by driving intragranuloma accumulation of neutrophils, which upon arrival adopt an inflammatory phenotype in an ESX-1-dependent manner. In contrast, monocytes limited the accumulation of neutrophils and neutrophil-mediated pathology via an iNOS-dependent mechanism, suggesting a major host-protective function for monocytes specifically by restricting ESX-1-dependent neutrophilic inflammation. These findings provide insight into how ESX-1 promotes disease, and they reveal an antagonistic functional relationship between monocytes and neutrophils that might regulate immunopathology not only in mycobacterial infection but also in other infections as well as in inflammatory conditions and cancer.

IRF8 deficiency induces the transcriptional, functional, and epigenetic reprogramming of cDC1 into the cDC2 lineage

Conventional dendritic cells (cDCs) consist of two major functionally and phenotypically distinct subsets, cDC1 and cDC2, whose development is dependent on distinct sets of transcription factors. Interferon regulatory factor 8 (IRF8) is required at multiple stages of cDC1 development, but its role in committed cDC1 remains unclear. Here, we used Xcre-cre to delete Irf8 in committed cDC1 and demonstrate that Irf8 is required for maintaining the identity of cDC1. In the absence of Irf8, committed cDC1 acquired the transcriptional, functional, and chromatin accessibility properties of cDC2. This conversion was independent of Irf4 and was associated with the decreased accessibility of putative IRF8, Batf3, and composite AP-1-IRF (AICE)-binding elements, together with increased accessibility of cDC2-associated transcription-factor-binding elements. Thus, IRF8 expression by committed cDC1 is required for preventing their conversion into cDC2-like cells.

Immune Profiling of Human Gut-Associated Lymphoid Tissue Identifies a Role for Isolated Lymphoid Follicles in Priming of Region-Specific Immunity

The intestine contains some of the most diverse and complex immune compartments in the body. Here we describe a method for isolating human gut-associated lymphoid tissues (GALTs) that allows unprecedented profiling of the adaptive immune system in submucosal and mucosal isolated lymphoid follicles (SM-ILFs and M-ILFs, respectively) as well as in GALT-free intestinal lamina propria (LP). SM-ILF and M-ILF showed distinct patterns of distribution along the length of the intestine, were linked to the systemic circulation through MAdCAM-1⁺ high endothelial venules and efferent lymphatics, and had immune profiles consistent with immune-inductive sites. IgA sequencing analysis indicated that human ILFs are sites where intestinal adaptive immune responses are initiated in an anatomically restricted manner. Our findings position ILFs as key inductive hubs for regional immunity in the human intestine, and the methods presented will allow future assessment of these compartments in health and disease.

The Peyer's Patch Mononuclear Phagocyte System at Steady State and during Infection

The gut represents a potential entry site for a wide range of pathogens including protozoa, bacteria, viruses, or fungi. Consequently, it is protected by one of the largest and most diversified population of immune cells of the body. Its surveillance requires the constant sampling of its encounters by dedicated sentinels composed of follicles and their associated epithelium located in specialized area. In the small intestine, Peyer’s patches (PPs) are the most important of these mucosal immune response inductive sites. Through several mechanisms including transcytosis by specialized epithelial cells called M-cells, access to the gut lumen is facilitated in PPs. Although antigen sampling is critical to the initiation of the mucosal immune response, pathogens have evolved strategies to take advantage of this permissive gateway to enter the host and disseminate. It is, therefore, critical to decipher the mechanisms that underlie both host defense and pathogen subversive strategies in order to develop new mucosal-based therapeutic approaches. Whereas penetration of pathogens through M cells has been well described, their fate once they have reached the subepithelial dome (SED) remains less well understood. Nevertheless, it is clear that the mononuclear phagocyte system (MPS) plays a critical role in handling these pathogens. MPS members, including both dendritic cells and macrophages, are indeed strongly enriched in the SED, interact with M cells, and are necessary for antigen presentation to immune effector cells. This review focuses on recent advances, which have allowed distinguishing the different PP mononuclear phagocyte subsets. It gives an overview of their diversity, specificity, location, and functions. Interaction of PP phagocytes with the microbiota and the follicle-associated epithelium as well as PP infection studies are described in the light of these new criteria of PP phagocyte identification. Finally, known alterations affecting the different phagocyte subsets during PP stimulation or infection are discussed.

Gene expression profiling of the Peyer's patch mononuclear phagocyte system

Peyer's patches (PPs) are primary inductive sites of mucosal immunity. The PP mononuclear phagocyte system, which encompasses both dendritic cells (DCs) and macrophages, is essential for the initiation of the mucosal immune response. We recently developed a method to isolate each mononuclear phagocyte subset of PP (Bonnardel et al., 2015). We performed a transcriptional analysis of three of these subsets: the CD11b(+) conventional DC, the lysozyme-expressing monocyte-derived DC termed LysoDC and the CD11c(hi) lysozyme-expressing macrophages. Here, we provide details of the gating strategy we used to isolate each phagocyte subset and show the quality controls and analysis associated with our gene array data deposited into Gene Expression Omnibus (GEO) under GSE65514.

Simultaneous removal of 2-chlorophenol, phenol, p-cresol and p-hydroxybenzaldehyde under nitrifying conditions: kinetic study

The kinetic behavior of a stable nitrifying consortium exposed to 2-chlorophenol (2-CP), phenol, p-cresol and p-hydroxybenzaldehyde (p-OHB) was evaluated in batch assays. Phenolic compounds were evaluated either individually or in mixture. In individual assays, 2-CP inhibited stronger the nitrification, diminishing the ammonium consumption efficiency (16%) and the nitrate production rate (at 91%). Nonetheless, the consumption efficiencies for all phenolics were of 100%. On the other hand, in mixture, the inhibitory effect of 2-CP diminished significantly, since ammonium consumption efficiency and nitrate production rate were improved. Consumption efficiencies for most of the phenolic compounds were high. Furthermore, the kinetic of 2-CP oxidation was 2.4-fold-faster than the individual assays. Finally, the experimental results showed the potential of nitrifying consortium for removing 2-CP, phenol, p-cresol and p-OHB. This is the first work showing the simultaneous removal of these pollutants and also this information might be useful for treating wastewaters of chemical complexity.

p-Cresol biotransformation by a nitrifying consortium

The oxidizing ability of a nitrifying consortium exposed to p-cresol (25 mg CL(-1)) was evaluated in batch cultures. Biotransformation of the phenolic compound was investigated by identifying the different intermediates formed. p-Cresol inhibited the ammonia-oxidizing process with a decrease of 83% in the specific rate of ammonium consumption. After 48 h, ammonium consumption efficiency was 96+/-9% while nitrate yield reached 0.95+/-0.06 g NO(3)(-)-Ng(-1)NH(4)(+)-N consumed. High value for nitrate production yield showed that the nitrifying metabolic pathway was only affected at the specific rate level being nitrate the main end product. The consortium was able to totally oxidize p-cresol at a specific rate of 0.17+/-0.06 mg p-cresol-Cmg(-1) microbial protein h(-1). p-Cresol was first transformed to p-hydroxybenzaldehyde and p-hydroxybenzoate, which were later completely mineralized. In the presence of allylthiourea, a specific inhibitor of ammonia monooxygenase (AMO), p-cresol was oxidized to the same intermediates and in a similar pattern as obtained without the AMO inhibitor. AMO seemed not to be involved in the p-cresol oxidation process. When p-hydroxybenzaldehyde was added (25 mg CL(-1)), the nitrifying process was inhibited in the same way as observed with p-cresol, indicating that p-hydroxybenzaldehyde could be the main compound responsible for nitrification inhibition. p-Hydroxybenzaldehyde was accumulated during 15 h before complete consumption at a specific rate value eight times lower than the p-cresol consumption rate. Results showed that p-hydroxybenzaldehyde oxidation was the limiting step in p-cresol mineralization by the nitrifying consortium.

Altering the time of the second gonadotropin-releasing hormone injection and artificial insemination (AI) during Ovsynch affects pregnancies per AI in lactating dairy cows

Based on previous research, we hypothesized that Cosynch at 72 h [GnRH-7 d-PGF(2alpha)-72 h-GnRH + artificial insemination (AI)] would result in a greater number of pregnancies per AI (P/AI) than Cosynch at 48 h. Further, we hypothesized that P/AI would be improved to a greater extent when GnRH was administered at 56 h after PGF(2alpha) before AI at 72 h due to a more optimal interval between the LH surge and AI. Nine hundred twenty-seven lactating dairy cows (n = 1,507 AI) were blocked by pen, and pens rotated through treatments. All cows received GnRH followed 7 d later by PGF(2alpha) and then received one of the following: 1) GnRH + timed AI 48 h after PGF(2alpha) (Cosynch-48); 2) GnRH 56 h after PGF(2alpha) + timed AI 72 h after PGF(2alpha) (Ovsynch-56); or 3) GnRH + timed AI 72 h after PGF(2alpha) (Cosynch-72). Pregnancy diagnoses were performed by ultrasound at 31 to 33 d post-AI and again at 52 to 54 d post-AI. Overall P/AI were similar for the Cosynch-48 (29.2%) and Cosynch-72 (25.4%) groups. The Ovsynch-56 group had a greater P/AI (38.6%) than Cosynch-48 or Cosynch-72. Presynchronized first-service animals had greater P/AI than cows at later services in Cosynch-48 (36.2 vs. 23.0%) and Ovsynch-56 (44.8 vs. 32.7%) but not in Cosynch-72 (24.6 vs. 26.2%). Similarly, primiparous cows had greater P/AI than multiparous cows in Cosynch-48 (34.1 vs. 22.9%) and Ovsynch-56 (41.3 vs. 32.6%), but not Cosynch-72 (29.8 vs. 25.3%). In conclusion, we found no advantage to Cosynch at 72 h vs. 48 h. In contrast, we found a clear advantage to treating with GnRH at 56 h, 16 h before a 72-h AI, probably because of more-optimal timing of AI before ovulation.

Acetylcholinesterase activities in marine snail (Cronia contracta) as a biomarker of neurotoxic contaminants along the Goa coast, West coast of India

The measurement of acetylcholinesterase (AChE) activity is used worldwide as a biomarker of environmental contamination due to neurotoxic substances. In the present study the AChE activities was measured in marine snails (Cronia contracta) collected seasonally from six sampling sites (viz. Arambol, Anjuna, Dona Paula, Vasco, Velsao and Palolem) along the Goa coast during the pre-monsoon (April, 2004), monsoon (September, 2004) and post-monsoon (November, 2004) periods. The AChE activities in C. contracta showed wide variation along the Goa coast. It was found to be quite high at the reference site, Palolem (23.97, 21.72 and 24.85) throughout the sampling period (April-November, 2004). The AChE activities in C. contracta decreased significantly at Vasco (44.6-52.4% reduction) followed by Dona Paula (24.9-36.2% reduction), Velasao (10.8-35.9% reduction), Arambol (12.6-37.3% reduction) and Anjuna (0-12.7% reduction). Such a significant variation of AChE activities in the marine snail along the Goa coast can be attributed to neurotoxic substances prevalent in those regions. The high concentration of different neurotoxic metals (lead, cadmium, copper, manganese and iron) and petroleum hydrocarbons in the tissues of the marine snails at Dona Paula, Vasco and Velsao clearly substantiate reduction of AChE activities in C. contracta. The in vitro studies on the inhibition of AChE by different metals and PHC indicated that lead, cadmium and copper are the most predominant inhibitor. Based on the AChE activities in C. contracta the sampling sites along the Goa coast can be classified into three major clusters such as highly contaminated sites (Dona Paula, Vasco and Velsao), moderately contaminated sites (Arambol, Anjuna) and least contaminated site (Palolem).

Central nervous system effects of the crude extract of Erythrina velutina on rodents

The aqueous extract (AE) of Erythrina velutina prolonged the sleep duration induced by sodium pentobarbital (control: 6.4 +/- 1.2 min; extract 10 mg/kg, 47.1 +/- 3.9 min; extract 100 mg/kg, 109.4 +/- 7.2 min; F = 243, P < 0.001). In the open field, the extract at the doses of 10 and 50 mg/kg did not changed the number of crossings, rearings nor groomings. On the other hand, at the dose of 200 mg/kg it reduced the number of crossings (q = 6.25, P < 0.05) and groomings (q = 3.91, P < 0.05). When exposed during three consecutive days to the open field, the control animals showed habituation for crossings (F = 17.56, P < 0.001) and rearings (F = 14.01, P < 0.001). The same was not true for animals treated with 10 mg/kg of the extract (crossings: F = 3.59, P > 0.05; rearings: F = 3.62, P > 0.05). At the same dose, the extract blocked the acquisition of foot shock memory (P = 0.9219) when compared to the control values (P = 0.0078). Our data showed that the crude extract of Erythrina velutina at lower doses interferes with mnemonic process for different tasks, while at higher doses, the sedative and neuromuscular blocking actions are the main effects.

Biochemical studies on leukocyte and fibroblast human beta-galactosidase

OBJECTIVES

Some biochemical characteristics of the human leukocyte and fibroblast beta-galactosidase were studied.

DESIGN AND METHODS

Leukocyte and fibroblast enzyme activity was determined fluorometricaly using 4-methylumbelliferyl-beta-D-galactoside as artificial substrate. Optimum pH, Km, Vmax and thermostability of the enzyme at 42 degrees C were determined.

RESULTS

The leukocyte and fibroblast enzyme has an optimum pH at 4.2, which is in agreement with the lysosomal origin of the enzyme. The Km of the enzyme was 0.62 in leukocytes and 0.67 in fibroblasts, and Vmax was 289.9 nmol/h/mg of protein and 1779.2 nmol/h/mg of protein in the two tissues, respectively. When fibroblast or leukocyte beta-galactosidase was pre-incubated at 42 degrees C, it did not retain its activity because the residual activity after 80 minutes of pre-incubation at this temperature was lower than 30% of the initial activity both in leukocytes and fibroblasts.

CONCLUSIONS

This was the first study of Km, Vmax and thermostability of beta-galactosidase performed on leukocytes and provided data for a better characterization of the enzyme beta-galactosidase, allowing the improvement of the analytical conditions.