Mesenteric lymph node stroma cells in the generation of intestinal immune responses

Effect of feeding fermented distiller's grains diets on immune status and metabolomics of spleen and mesenteric lymph nodes in finishing cattle

To explore the effect of feeding fermented distiller's grains (FDG) diets on spleen and mesenteric lymph nodes (MLN) immune status and metabolomics in finishing cattle, eighteen Guanling crossbred cattle (18 months old, 250.0 ± 25 kg) were randomly divided into 3 groups: a basal diet (Control) group, an FDG-15% group, and an FDG-30% group (containing 0%, 15% and 30% FDG to partially replace the concentrates, respectively). After 75 days, the spleens and MLN were collected for detection of relative spleen weight, immune parameters, and metabolomic analysis. Compared with the Control group, FDG-30% group significantly increased (P<0.05) the relative spleen weight. In addition, the level of IL-17A in the spleen of the FDG-30% group was significantly higher than that of the FDG-15% group. Metabolomic analysis showed that differential metabolites (VIP＞1, P＜0.05) of spleen and MLN in FDG-15% and FDG-30% groups are mostly lipids and lipid molecules. KEGG analysis illustrated that choline metabolism in cancer, glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids and insulin resistance were metabolic pathways in spleen shared by FDG-15% group vs.Control group and FDG-30% group vs.Control group, and choline metabolism in cancer was a metabolic pathway in MLN shared by FDG-15% group vs.Control group and FDG-30% group vs.Control group. These results suggest that feeding FDG may promote spleen development by regulating choline metabolism in cancer, glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids and insulin resistance. Additionally, it may affect MLN development by regulating choline metabolism in cancer. SIGNIFICANCE: Fermented distiller's grains (FDG) is a high quality alternative to feed because it is rich in beneficial microorganisms and nutrients. The spleen and mesenteric lymph nodes (MLN) are important peripheral immune organs in animals, whose status reflects the health of the animal. However, there are few reports on the effect of feeding FDG diets on spleen and MLN immune status and metabolomics in domestic animals. In this study, we found that feeding FDG may promote spleen development by regulating choline metabolism in cancer, glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids and insulin resistance metabolic pathways, and may affect MLN development by regulating choline metabolism in cancer. This study extends our understanding of the metabolomics of the spleen and MLN in FDG and helps to further understand of the immunomodulatory effects of the FDG diet.

Mild heat stress-induced adaptive immune response in blood mononuclear cells and leukocytes from mesenteric lymph nodes of primiparous lactating Holstein cows

Heat stress negatively affects the metabolism and physiology of the bovine gut. However, it is not known whether heat stress induces an inflammatory response in mesenteric lymph nodes (MLN), the primary origin of gut immune cells, and thus contributes to inflammatory processes in the circulation. Therefore, our objective was to elucidate the effects of chronic heat stress on the systemic activation of acute-phase response in blood, proinflammatory cytokine production in peripheral blood mononuclear cells (PBMC), and the activation of the toll-like receptor signaling (TLR) 2/4 pathway in MLN leucocytes and their chemokines and chemokine receptor profiles in Holstein cows. Primiparous Holstein cows (n = 30; 169 ± 9 d in milk) were exposed to a temperature-humidity index (THI) of 60 [16°C, 63% relative humidity (RH)] for 6 d. Thereafter, cows were evenly assigned to 3 groups: heat-stressed (HS; 28°C, 50% RH, THI = 76), control (CON; 16°C, 69% RH, THI = 60), or pair-feeding (PF; 16°C, 69% RH, THI = 60) for 7 d. On d 6, PBMC were isolated and on d 7 MLN. Plasma haptoglobin, TNFα, and IFNγ concentrations increased more in HS than CON cows. Concomitantly, TNFA mRNA abundance was higher in PBMC and MLN leucocytes of HS than PF cows, whereas IFNG mRNA abundance tended to be higher in MLN leucocytes of HS than PF cows, but not for chemokines (CCL20, CCL25) or chemokine receptors (ITGB7, CCR6, CCR7, CCR9). Furthermore, the TLR2 protein expression tended to be more abundant in MLN leucocytes of HS than PF cows. These results suggest that heat stress induced an adaptive immune response in blood, PBMC, and MLN leukocytes involving the acute-phase protein haptoglobin, proinflammatory cytokine production, and TLR2 signaling in MLN leucocytes. However, chemokines regulating the leucocyte trafficking between MLN and gut seem not to be involved in the adaptive immune response to heat stress.

Time-restricted feeding ameliorates dextran sulfate sodium-induced colitis via reducing intestinal inflammation

Time-restricted feeding (TRF) is an emerging dietary intervention that improves metabolic disorders such as obesity, insulin resistance and dyslipidemia. Inflammatory bowel disease (IBD) is a chronic inflammatory disorder affecting the gastrointestinal tract, where nutrition plays an important role in its pathogenesis. Although numerous strategies of nutritional intervention have been reported, whether TRF can improve IBD has been elusive. In this study, we investigated the effect of two cycles of 7-day TRF intervention in a dextran sulfate sodium-induced IBD mouse model. We found that TRF was able to reduce the disease activity index and ameliorate the IBD-associated symptoms, as well as increase the number of colonic crypts and decrease the histological score in the colon. Furthermore, TRF lowered the percentage of CD4⁺ T cells in the peripheral blood and mesenteric lymph node, and increased the number of CD4⁺CD25⁺ T cells in the mesenteric lymph nodes. Additionally, TRF reduced the infiltration of leukocytes and macrophages around the crypt base in the colon. However, unlike the intermittent caloric restriction with fasting-mimicking diet, TRF was not able to increase the markers of progenitor and cell proliferation in the colon. Collectively, these results demonstrated that TRF is able to improve IBD in mice via reduction in intestinal inflammation.

Co-Expression of the B-Cell Key Transcription Factors Blimp-1 and IRF4 Identifies Plasma Cells in the Pig

Antibody-secreting plasma cells (PCs) have remained largely uncharacterized for years in the field of porcine immunology. For an in-depth study of porcine PCs, we identified cross-reactive antibodies against three key transcription factors: PR domain zinc finger protein-1 (Blimp-1), interferon regulatory factor 4 (IRF4), and paired box 5 (Pax5). A distinct Blimp-1⁺IRF4⁺ cell population was found in cells isolated from blood, spleen, lymph nodes, bone marrow, and lung of healthy pigs. These cells showed a downregulation of Pax5 compared to other B cells. Within Blimp-1⁺IRF4⁺ B cells, IgM-, IgG-, and IgA-expressing cells were identified and immunoglobulin-class distribution was clearly different between the anatomical locations, with IgA⁺ PCs dominating in lung tissue and IgM⁺ PCs dominating in the spleen. Expression patterns of Ki-67, MHC-II, CD9, and CD28 were investigated in the different organs. A high expression of Ki-67 was observed in blood, suggesting a plasmablast stage. Blimp-1⁺IRF4⁺ cells showed an overall lower expression of MHC-II compared to regular B cells, confirming a progressive loss in B-cell differentiation toward the PC stage. CD28 showed slightly elevated expression levels in Blimp-1⁺IRF4⁺ cells in most organs, a phenotype that is also described for PCs in mice and humans. This was not seen for CD9. We further developed a FACS-sorting strategy for live porcine PCs for functional assays. CD3^-CD16^-CD172a^– sorted cells with a CD49d^highFSC-A^high phenotype contained Blimp-1⁺IRF4⁺ cells and were capable of spontaneous IgG production, thus confirming PC identity. These results reveal fundamental phenotypes of porcine PCs and will facilitate the study of this specific B-cell subset in the future.

Complementary Lipidomic, Proteomic, and Mass Spectrometry Imaging Approach to the Characterization of the Acute Effects of Radiation in the Non-human Primate Mesenteric Lymph Node after Partial-body Irradiation with Minimal Bone Marrow Sparing

ABSTRACT

Radiation sequelae is complex and characterized by multiple pathologies, which occur over time and nonuniformly throughout different organs. The study of the mesenteric lymph node (MLN) due to its importance in the gastrointestinal system is of particular interest. Other studies have shown an immediate post-irradiation reduction in cellularity due to the known effects of irradiation on lymphoid cell populations, but the molecular and functional mechanisms that lead to these cellular alterations remain limited. In this work, we show the use of lipidomic, proteomic, and mass spectrometry imaging in the characterization of the effects of acute radiation exposure on the MLN at different time points after ionizing radiation (IR) from 4 d to 21 d after 12 Gy partial body irradiation with 2.5% bone marrow sparing. The combined analyses showed a dysregulation of the lipid and protein composition in the MLN after IR. Protein expression was affected in numerous pathways, including pathways regulating lipids such as LXR/RXR activation and acute phase response. Lipid distribution and abundance was also affected by IR in the MLN, including an accumulation of triacylglycerides, a decrease in polyunsaturated glycerophospholipids, and changes in polyunsaturated fatty acids. Those changes were observed as early as 4 d after IR and were more pronounced for lipids with a higher concentration in the nodules and the medulla of the MLN. These results provide molecular insight into the MLN that can inform on injury mechanism in a non-human primate model of the acute radiation syndrome of the gastrointestinal tract. Those findings may contribute to the identification of therapeutic targets and the development of new medical countermeasures.

Interplay between Gut Lymphatic Vessels and Microbiota

Lymphatic vessels play a distinctive role in draining fluid, molecules and even cells from interstitial and serosal spaces back to the blood circulation. Lymph vessels of the gut, and especially those located in the villi (called lacteals), not only serve this primary function, but are also responsible for the transport of lipid moieties absorbed by the intestinal mucosa and serve as a second line of defence against possible bacterial infections. Here, we briefly review the current knowledge of the general mechanisms allowing lymph drainage and propulsion and will focus on the most recent findings on the mutual relationship between lacteals and intestinal microbiota.

Mesenteric Lymph Node Transplantation in Mice to Study Immune Responses of the Gastrointestinal Tract

Mesenteric lymph nodes (mLNs) are sentinel sites of enteral immunosurveillance and immune homeostasis. Immune cells from the gastrointestinal tract (GIT) are constantly recruited to the mLNs in steady-state and under inflammatory conditions resulting in the induction of tolerance and immune cells activation, respectively. Surgical dissection and transplantation of lymph nodes (LN) is a technique that has supported seminal work to study LN function and is useful to investigate resident stromal and endothelial cell biology and their cellular interactions in experimental disease models. Here, we provide a detailed protocol of syngeneic mLN transplantation and report assays to analyze effective mLN engraftment in congenic recipients. Transplanted mLNs allow to study T cell activation and proliferation in preclinical mouse models. Donor mLNs proved viable and functional after surgical transplantation and regenerated blood and lymphatic vessels. Immune cells from the host completely colonized the transplanted mLNs within 7-8 weeks after the surgical intervention. After allogeneic hematopoietic cell transplantation (allo-HCT), adoptively transferred allogeneic CD4+ T cells from FVB/N (H-2q) mice homed to the transplanted mLNs in C57BL/6 (H-2b) recipients during the initiation phase of acute graft-versus-host disease (aGvHD). These CD4+ T cells retained full proliferative capacity and upregulated effector and gut homing molecules comparable to those in mLNs from unmanipulated wild-type recipients. Wild type mLNs transplanted into MHCII deficient syngeneic hosts sufficed to activate alloreactive T cells upon allogeneic hematopoietic cell transplantation, even in the absence of MHCII+ CD11c+ myeloid cells. These data support that orthotopically transplanted mLNs maintain physiological functions after transplantation. The technique of LN transplantation can be applied to study migratory and resident cell compartment interactions in mLNs as well as immune reactions from and to the gut under inflammatory and non-inflammatory conditions.

Estrogen-induced neuroimmunomodulation as facilitator of and barrier to reproductive aging in brain and lymphoid organs

Reproductive aging in females is marked by alterations in gonadal hormones, estrogen and progesterone, that facilitate cessation of reproductive cycles and onset of female-specific diseases such as autoimmune and neurodegenerative diseases, hormone-dependent cancers, and osteoporosis. Bidirectional communication between the three homeostatic systems, nervous system, endocrine system, and immune system, is essential for the maintenance of health and any dysfunction in the cross-talk promotes the development of diseases and cancer. The pleiotropic effects of estrogen on neural-immune interactions may promote either neuroprotection or inflammatory conditions depending on the site of action, dose and duration of treatment, type of estrogen receptors and its influence on intracellular signaling pathways, etc. Our studies involving treatment of early middle-aged female rats with low and high doses of estrogen and examining the brain areas, thymus, spleen, and lymph nodes revealed that estrogen-induced changes in neural-immune interactions are markedly affected in thymus followed by spleen and lymph nodes while it confers neuroprotection in the brain areas. These alterations are determined by antioxidant enzyme status, growth factors, intracellular signaling pathways involved in cell survival and inflammation, and metabolic enzymes and thus, may regulate the various stages in female reproductive aging. It is imperative that detailed longitudinal studies are carried out to understand the mechanisms of neuroendocrine-immune interactions in reproductive aging to facilitate healthy aging and for the development of better treatment strategies for female-specific diseases.

Environmental-mediated intestinal homeostasis in neonatal mice

BACKGROUND

Immunoglobulin A (IgA) plays a key role in coating luminal antigens and preventing translocation of harmful bacteria. The aryl hydrocarbon receptor (AhR) is a basic helix-loop-helix transcription factor that when stimulated activates factors important for barrier function and intestinal homeostasis. We hypothesize that AhR signaling is critical for establishment of intestinal homeostasis in neonates.

MATERIAL AND METHODS

Mice: C57BL/6 (B6) AhR+/+ wild type (WT), B6.AhR-/- Aryl-hydrocarbon receptor knockout (KO), and B6.AhR+/+ raised on an AhR ligand-free diet (AhR LF). Enzyme-linked immunosorbent assay was used to measure fecal and serum IgA levels. Bacterial translocation was measured by culturing the mesenteric lymph nodes.

RESULTS

Two week old KO mice had significantly less fecal IgA compared with WT (and AhR LF, P value = 0.0393. The amount of IgA from the gastric contents of 2-wk-old mice was not significantly different. At age 8 wk, AhR LF mice had significantly less fecal IgA than WT and KO P value = 0.0077. At 2 wk, KO mice had significantly higher levels of bacterial translocation and at 8 wk AhR LF had significantly higher levels of bacterial translocation compared with WT.

CONCLUSIONS

In neonatal mice, the lack of AhR signaling is associated with loss of intestinal homeostasis, evidenced by decreased levels of IgA and increased bacterial translocation. In adult mice, exogenous AhR ligand and not receptor signaling is necessary for maintenance of intestinal integrity.

Cytokine, antibody and proliferative cellular responses elicited by Taenia solium calreticulin upon experimental infection in hamsters

Taenia solium causes two diseases in humans, cysticercosis and taeniosis. Tapeworm carriers are the main risk factor for neurocysticercosis. Limited information is available about the immune response elicited by the adult parasite, particularly the induction of Th2 responses, frequently associated to helminth infections. Calreticulin is a ubiquitous, multifunctional protein involved in cellular calcium homeostasis, which has been suggested to play a role in the regulation of immune responses. In this work, we assessed the effect of recombinant T. solium calreticulin (rTsCRT) on the cytokine, humoral and cellular responses upon experimental infection in Syrian Golden hamsters (Mesocricetus auratus). Animals were infected with T. solium cysticerci and euthanized at different times after infection. Specific serum antibodies, proliferative responses in mesenteric lymph nodes and spleen cells, as well as cytokines messenger RNA (mRNA) were analyzed. The results showed that one third of the infected animals elicited anti-rTsCRT IgG antibodies. Interestingly, mesenteric lymph node (MLN) cells from either infected or non-infected animals did not proliferate upon in vitro stimulation with rTsCRT. Additionally, stimulation with a tapeworm crude extract resulted in increased expression of IL-4 and IL-5 mRNA. Upon stimulation, rTsCRT increased the expression levels of IL-10 in spleen and MLN cells from uninfected and infected hamsters. The results showed that rTsCRT favors a Th2-biased immune response characterized by the induction of IL-10 in mucosal and systemic lymphoid organs. Here we provide the first data on the cytokine, antibody and cellular responses to rTsCRT upon in vitro stimulation during taeniasis.

Native adipose stromal cells egress from adipose tissue in vivo: evidence during lymph node activation

Adipose tissue (AT) has become accepted as a source of multipotent progenitor cells, the adipose stromal cells (ASCs). In this regard, considerable work has been performed to harvest and characterize this cell population as well as to investigate the mechanisms by which transplanted ASCs mediate tissue regeneration. In contrast the endogenous release of native ASCs by AT has been poorly investigated. In this work, we show that native ASCs egress from murine AT. Indeed, we demonstrated that the release of native ASCs from AT can be evidenced both using an ex vivo perfusion model that we set up and in vivo. Such a mobilization process is controlled by CXCR4 chemokine receptor. In addition, once mobilized from AT, circulating ASCs were found to navigate through lymph fluid and to home into lymph nodes (LN). Therefore, we demonstrated that, during the LN activation, the fat depot encapsulating the activated LN releases native ASCs, which in turn invade the activated LN. Moreover, the ASCs invading the LN were visualized in close physical interaction with podoplanin and ER-TR7 positive structures corresponding to the stromal network composing the LN. This dynamic was impaired with CXCR4 neutralizing antibody. Taken together, these data provide robust evidences that native ASCs can traffic in vivo and that AT might provide stromal cells to activated LNs.

Human immunity in vitro - solving immunogenicity and more

It has been widely recognised that the phylogenetic distance between laboratory animals and humans limits the former's predictive value for immunogenicity testing of biopharmaceuticals and nanostructure-based drug delivery and adjuvant systems. 2D in vitro assays have been established in conventional culture plates with little success so far. Here, we detail the status of various 3D approaches to emulate innate immunity in non-lymphoid organs and adaptive immune response in human professional lymphoid immune organs in vitro. We stress the tight relationship between the necessarily changing architecture of professional lymphoid organs at rest and when activated by pathogens, and match it with the immunity identified in vitro. Recommendations for further improvements of lymphoid tissue architecture relevant to the development of a sustainable adaptive immune response in vitro are summarized. In the end, we sketch a forecast of translational innovations in the field to model systemic innate and adaptive immunity in vitro.

Mucosal and systemic T cell response in mice intragastrically infected with Neospora caninum tachyzoites

The murine model has been widely used to study the host immune response to Neospora caninum. However, in most studies, the intraperitoneal route was preferentially used to establish infection. Here, C57BL/6 mice were infected with N. caninum tachyzoites by the intragastric route, as it more closely resembles the natural route of infection through the gastrointestinal tract. The elicited T-cell mediated immune response was evaluated in the intestinal epithelium and mesenteric lymph nodes (MLN). Early upon the parasitic challenge, IL-12 production by conventional and plasmacytoid dendritic cells was increased in MLN. Accordingly, increased proportions and numbers of TCRαβ+CD8+IFN-γ+ lymphocytes were detected, not only in the intestinal epithelium and MLN, but also in the spleen of the infected mice. In this organ, IFN-γ-producing TCRαβ+CD4+ T cells were also found to increase in the infected mice, however later than CD8+ T cells. Interestingly, splenic and MLN CD4+CD25+ T cells sorted from infected mice presented a suppressive activity on in vitro T cell proliferation and cytokine production above that of control counterparts. These results altogether indicate that, by producing IFN-γ, TCRαβ+CD8+ cells contribute for local and systemic host protection in the earliest days upon infection established through the gastrointestinal tract. Nevertheless, they also provide substantial evidence for a parasite-driven reinforcement of T regulatory cell function which may contribute for parasite persistence in the host and might represent an additional barrier to overcome towards effective vaccination.

On the road to tolerance--generation and migration of gut regulatory T cells

The intestinal immune system potently supports the generation of induced Treg (iTreg) cells. Within intestinal lymphoid compartments iTreg cells receive homing cues, which direct these cells to the gut lamina propria where they expand and locally suppress immune responses. Yet iTreg cells are but one side of a coin, the other side of which comprises natural Treg (nTreg) cells generated in the thymus. nTreg cells, which act in concert with iTreg cells, also acquire a diversified pattern of homing receptors. Thus iTreg and nTreg cells can enter the gut, and draining lymph nodes to cooperatively ensure intestinal homeostasis.

Stromal regulation of human gastric dendritic cells restricts the Th1 response to Helicobacter pylori

BACKGROUND & AIMS

Mucosal dendritic cells (DCs) play a key role in initiating the T-helper (Th)1 response to Helicobacter pylori. To further elucidate the mucosal response to H pylori, we examined whether gastric stromal factors condition DCs to support tolerance to H pylori, analogous to intestinal stromal factor-driven macrophage tolerance to commensal bacteria.

METHODS

To model mucosal DC development, we isolated and cultured cell-depleted human stroma/extracellular matrix from fresh gastric and intestinal mucosa to generate stroma-conditioned media. We then analyzed the capacity of stroma-conditioned media-treated monocyte-derived DCs and primary human gastric and intestinal DCs pulsed in vitro with H pylori to induce T-cell proliferation and interferon gamma secretion.

RESULTS

Stromal factors in gastric mucosa suppressed H pylori-stimulated DC activation and the ability of DCs to drive a Th1 proliferative and cytokine response to H pylori. The ability of gastric stromal factors to down-regulate DC function was similar to that of intestinal stromal factors and was independent of transforming growth factor β, prostaglandin E₂, interleukin (IL)-10, and thymic stromal lymphopoietin. Stroma-conditioned media-induced reduction in DC-stimulated Th1 responses was associated with reduced DC release of IL-12.

CONCLUSIONS

Gastric stromal factors down-regulate DC responsiveness to H pylori, resulting in a dampened gastric Th1 response. We speculate that stroma-induced down-regulation of DC function contributes to the permissiveness of both gastric and intestinal mucosa to colonization by persistent residential microbes.

Role of lymphatic vessels in tumor immunity: passive conduits or active participants?

Research in lymphatic biology and cancer immunology may soon intersect as emerging evidence implicates the lymphatics in the progression of chronic inflammation and autoimmunity as well as in tumor metastasis and immune escape. Like the blood vasculature, the lymphatic system comprises a highly dynamic conduit system that regulates fluid homeostasis, antigen transport and immune cell trafficking, which all play important roles in the progression and resolution of inflammation, autoimmune diseases, and cancer. This review presents emerging evidence that lymphatic vessels are active modulators of immunity, perhaps fine-tuning the response to adjust the balance between peripheral tolerance and immunity. This suggests that the tumor-associated lymphatic vessels and draining lymph node may be important in tumor immunity which in turn governs metastasis.