Regulatory B10 cells play a protective role in severe acute pancreatitis

Intestinal Mucosal Immune Barrier: A Powerful Firewall Against Severe Acute Pancreatitis-Associated Acute Lung Injury via the Gut-Lung Axis

The pathogenesis of severe acute pancreatitis-associated acute lung injury (SAP-ALI), which is the leading cause of mortality among hospitalized patients in the intensive care unit, remains incompletely elucidated. The intestinal mucosal immune barrier is a crucial component of the intestinal epithelial barrier, and its aberrant activation contributes to the induction of sustained pro-inflammatory immune responses, paradoxical intercellular communication, and bacterial translocation. In this review, we firstly provide a comprehensive overview of the composition of the intestinal mucosal immune barrier and its pivotal roles in the pathogenesis of SAP-ALI. Secondly, the mechanisms of its crosstalk with gut microbiota, which is called gut-lung axis, and its effect on SAP-ALI were summarized. Finally, a number of drugs that could enhance the intestinal mucosal immune barrier and exhibit potential anti-SAP-ALI activities were presented, including probiotics, glutamine, enteral nutrition, and traditional Chinese medicine (TCM). The aim is to offer a theoretical framework based on the perspective of the intestinal mucosal immune barrier to protect against SAP-ALI.

Circulating Blood Lymphocytes and Acute Pancreatitis Severity: A Systematic Review

Acute pancreatitis is an acute inflammatory process of the pancreas with high prevalence and varying degrees of severity that can be potentially life-threatening. Much is still unknown about which mechanisms determine the course and severity of acute pancreatitis. The primary objective of this review is to identify the potential association between circulating lymphocytes and the severity of acute pancreatitis. A systematic search was performed in Medline, Web of Science, Cochrane Central Register of Controlled Trials and ClinicalTrails.gov. The authors independently did the selection process as well as data extraction that was recorded into a flow diagram following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). Our initial search identified 27,783 studies which were narrowed down to 13 by applying strict inclusion and exclusion algorithms. The consistent findings across the studies indicated that peripheral blood lymphocytes are related to acute pancreatitis severity.

Repeated Stimulation of Toll-Like Receptor 2 and Dectin-1 Induces Chronic Pancreatitis in Mice Through the Participation of Acquired Immunity

BACKGROUND

Stimulation of Toll-like receptor 3 (TLR3) induces autoimmune-mediated pancreatitis in susceptible mice, whereas stimulation of TLR4 causes nonautoimmune-mediated pancreatitis. However, the effects of TLR2 stimulation on the pancreas are unknown.

AIMS

We investigated the role of TLR2 stimulation on pancreatic damage by repeatedly stimulating mice with TLR2 ligands.

METHODS

Wild-type (WT) and interleukin 10-deficient (IL-10-knockout (KO)) mice were administered zymosan and lipoteichoic acid (LTA) intraperitoneally at various doses twice weekly for 4 weeks. Syngeneic T-cell-deficient mice, B-cell-deficient mice, recombination activating gene 2-deficient (RAG2-KO) mice and RAG2-KO mice that had been reconstituted with CD4⁺ or CD8⁺ T cells isolated from WT mice were treated with zymosan similarly. Mice were killed, the severity of pancreatitis was graded histologically, and serum cytokine levels were measured.

RESULTS

Repeated administration of zymosan induced pancreatitis dose dependently in both WT and IL-10-KO mice. Administration of LTA induced pancreatitis only in IL-10-KO mice. Adoptive transfer of splenocytes obtained from IL-10-KO mice with pancreatitis did not cause pancreatitis in recipient RAG2-KO mice. Pancreatitis was scarcely observed in RAG2-KO mice and was attenuated in T-cell-deficient and B-cell-deficient mice compared with WT mice. A single administration of zymosan significantly increased the serum level of monocyte chemoattractant protein 1 (MCP-1) in WT mice.

CONCLUSIONS

Repeated stimulation of TLR2 and dectin-1 induced nonautoimmune-mediated pancreatitis in mice. Participation of acquired immunity seems to play an important role in the pathogenesis of pancreatitis in association with the increase in serum MCP-1 level.

The role of B regulatory (B10) cells in inflammatory disorders and their potential as therapeutic targets

Over the past decade, studies have identified subset of B cells, which play suppressive functions in additions to the conventional functions of B cells: antigen processing and presentation, activation of T cells and antibody productions. Because of their regulatory function, they were named as B regulatory cells (Bregs). Bregs restrict the severity of autoimmune disorders in animal disease models such as experimental autoimmune myocarditis (EAM), experimental autoimmune encephalitis (EAE), and collagen-induced arthritis (CIA) but can contribute to the development of infection and cancer. In humans, the roles of B regulatory cells in autoimmune diseases have not been clearly established because of the inconsistent findings from many researchers. This is believed to arise from the speculated fact that Bregs lack specific marker, which can be used to identify and characterize them in human diseases. The CD19⁺CD24^hiCD38^hiCD1d^hiB cells have been associated with the regulatory function. Available evidences highlight the relevance of increasing IL-10-producing B cells in autoimmune diseases and the possibility of serving as new therapeutic targets in inflammatory disorders. This review empanels the functions of Bregs in autoimmune diseases in both human and animal models, and further evaluates the possibility of Bregs as therapeutic targets in inflammatory disorders. Consequently, this might help identify possible research gaps, which need to be clarified as researchers speculate the possibility of targeting some subsets of Bregs in the treatment of inflammatory disorders.

Isolation of B-cells using Miltenyi MACS bead isolation kits

This article describes the procedures used to isolate pure B-cell populations from whole blood using various Miltenyi magnetic-activated cell sorting (MACS) bead Isolation kits. Such populations are vital for studies investigating the functional capacity of B-cells, as the presence of other cell types may have indirect effects on B-cell function through cell-cell interactions or by secretion of several soluble molecules. B-cells can be isolated by two main approaches: 1) Negative selection—in which B-cells remain “untouched” in their native state; this is advantageous as it is likely that B-cells remain functionally unaltered by this process. 2) Positive selection–in which B-cells are labelled and actively removed from the sample. We used three Negative B-cell isolation kits as well as the Positive B-cell isolation kit from Miltenyi and compared the purity of each of the resulting B-cells fractions. Contamination of isolated B-cell fractions with platelets was the conclusive finding for all of the isolation techniques tested. These results illustrate the inefficiency of current available MACS B-cell isolation kits to produce pure B-cell populations, from which concrete findings can be made. As such we suggest cell sorting as the preferred method for isolating pure B-cells to be used for downstream functional assays.

Cancer Stem Cells and Immunosuppressive Microenvironment in Glioma

Glioma is one of the most common malignant tumors of the central nervous system and is characterized by extensive infiltrative growth, neovascularization, and resistance to various combined therapies. In addition to heterogenous populations of tumor cells, the glioma stem cells (GSCs) and other nontumor cells present in the glioma microenvironment serve as critical regulators of tumor progression and recurrence. In this review, we discuss the role of several resident or peripheral factors with distinct tumor-promoting features and their dynamic interactions in the development of glioma. Localized antitumor factors could be silenced or even converted to suppressive phenotypes, due to stemness-related cell reprogramming and immunosuppressive mediators in glioma-derived microenvironment. Furthermore, we summarize the latest knowledge on GSCs and key microenvironment components, and discuss the emerging immunotherapeutic strategies to cure this disease.

Decreased levels of regulatory B cells in patients with acute pancreatitis: association with the severity of the disease

Early stratification of the severity of acute pancreatitis (AP) is clinically important. Regulatory B cells have been found to be associated with disease activity of autoimmune diseases. However, the role of Regulatory B cells in AP remains unknown. We investigate the dynamic longitudinal changes in circulating IL-10-producing B cells (B10) and memory CD19+CD24hiCD27hi cells in patients with AP to evaluate their prediction utility for AP severity. B10, CD19+CD24hiCD27hi cells, inflammatory markers and cytokines were detected in patients with AP immediately after admission to the hospital (day 1), then on the third and seventh days. We observed decreases in lymphocytes, CD19+, B10, CD19+CD24hiCD27hi cells and lower mean fluorescence intensity (MFI) of CD80 and CD86 on B10 or CD19+CD24hiCD27hi cells in patients with AP, especially in those with severe acute pancreatitis (SAP). CD19+CD24hiCD27hi cells from patients with AP suppressed the cytokine productions of CD4+ T cells and CD14+ monocytes, but had impaired ability to induce regulatory T cells response. B10 and CD19+CD24hiCD27hi cells significantly increased in patients with mild acute pancreatitis (MAP) from day 1 to day 7, whereas these indexes remained stable in patients with SAP. B10 or CD19+CD24hiCD27hi cells were negatively correlated with the severity index (APACHE II score), inflammatory markers (C-reactive protein, CD64 index), and cytokines (IL-6, IL-17, TNF-α). Furthermore, receiver operating characteristic (ROC) curve analysis revealed that B10 and CD19+CD24hiCD27hi cells could predict the development of SAP. Thus, the detection of B10 and CD19+CD24hiCD27hi cells may be a practical way to improve the early assessment of AP severity.

Effect of Endotoxemia in Suckling Rats on Pancreatic Integrity and Exocrine Function in Adults: A Review Report

Background. Endotoxin (LPS), the component of Gram-negative bacteria, is responsible for sepsis and neonatal mortality, but low concentrations of LPS produced tissue protection in experimental studies. The effects of LPS applied to the suckling rats on the pancreas of adult animals have not been previously explored. We present the impact of neonatal endotoxemia on the pancreatic exocrine function and on the acute pancreatitis which has been investigated in the adult animals. Endotoxemia was induced in suckling rats by intraperitoneal application of LPS from Escherichia coli or Salmonella typhi. In the adult rats, pretreated in the early period of life with LPS, histological manifestations of acute pancreatitis have been reduced. Pancreatic weight and plasma lipase activity were decreased, and SOD concentration was reversed and accompanied by a significant reduction of lipid peroxidation products (MDA + 4 HNE) in the pancreatic tissue. In the pancreatic acini, the significant increases in protein signals for toll-like receptor 4 and for heat shock protein 60 were found. Signal for the CCK1 receptor was reduced and pancreatic secretory responses to caerulein were diminished, whereas basal enzyme secretion was unaffected. These pioneer studies have shown that exposition of suckling rats to endotoxin has an impact on the pancreas in the adult organism.

Dysbiosis of intestinal microbiota and decrease in paneth cell antimicrobial peptide level during acute necrotizing pancreatitis in rats

OBJECTIVES

Intestinal barrier dysfunction plays an important role in acute necrotizing pancreatitis (ANP) and intestinal microbiota dysbiosis was involved in intestinal barrier failure. Paneth cells protect intestinal barrier and are associated with intestinal microbiota. Here, we investigated changes in intestinal microbiota and antimicrobial peptides of Paneth cells in ileum during ANP.

METHODS

Rats with ANP were established by retrograde injection of 3.5% sodium taurocholate into biliopancreatic duct and sacrificed at 24h and 48h, respectively. Injuries of pancreas and distal ileum were evaluated by histopathological score. Intestinal barrier function was assessed by plasma diamine oxidase activity (DAO) and D-lactate. Systemic and intestinal inflammation was evaluated by TNFα, IL-1β and IL-17A concentration by ELISA, respectively. 16S rRNA high throughput sequencing on fecal samples was used to investigate the changes in intestinal microbiota in the ANP group at 48h. Lysozyme and α-defensin5 were measured by real-time PCR, western blot and immunofluoresence.

RESULTS

ANP rats had more severe histopathological injuries in pancreas and distal ileum, injured intestinal barrier and increased expression of TNFα, IL-1β and IL-17A in plasma and distal ileum compared with those of the sham-operated (SO) group. Principal component analysis (PCA) showed structural segregation between the SO and ANP groups. Operational taxonomic unit (OTU) number and ACE index revealed decreased microbiota diversity in the ANP group. Taxonomic analysis showed dysbiosis of intestinal microbiota structure. At phyla level, Saccharibacteria and Tenericutes decreased significantly. At genus level, Escherichia-Shigella and Phascolarctobacterium increased significantly, while Candidatus_Saccharimonas, Prevotellaceae_UCG-001, Lachnospiraceae_UCG-001, Ruminiclostridium_5 and Ruminococcaceae_UCG-008 decreased significantly. Lysozyme and α-defensin5 mRNA expression levels decreased significantly in ANP group at 48h. Protein expression of lysozyme decreased in ANP groups at 24h and 48h. Meanwhile, the relative abundance of Escherichia-Shigella correlated inversely with the decrease in lysozyme.

CONCLUSION

The disorder in intestinal microbiota and decreases of Paneth cell antimicrobial peptides might participate in the pathogenesis of intestinal barrier dysfunction during ANP.

Different phenotypes of monocytes in patients with new-onset mild acute pancreatitis

AIM

To evaluate the numbers of different subsets of monocytes and their associations with the values of clinical measures in mild acute pancreatitis (MAP) patients.

METHODS

The study included one group of 13 healthy controls and another group of 24 patients with new-onset MAP. The numbers of different subsets of monocytes were examined in these two groups of subjects by flow cytometry. The concentrations of plasma interleukin (IL)-10 and IL-12 were determined by cytometric bead array. The acute physiology and chronic health evaluation (APACHE) II scores of individual patients were evaluated, and the levels of plasma C-reactive protein (CRP) as well as the activities of amylase and lipase were measured.

RESULTS

In comparison with that in the controls, significantly increased numbers of CD14+CD163-, CD14+CD163-MAC387+ M1 monocytes, but significantly reduced numbers of CD14+CD163+IL-10+ M2 monocytes were detected in the MAP patients (P < 0.01 or P < 0.05). Furthermore, significantly higher levels of plasma IL-10 and IL-12 were observed in the MAP patients (P < 0.01 for all). More importantly, the levels of plasma CRP were positively correlated with the numbers of CD14+CD163- (R = 0.5009, P = 0.0127) and CD14+CD163-MAC387+ (R = 0.5079, P = 0.0113) M1 monocytes and CD14+CD163+CD115+ M2 monocytes (R = 0.4565, P = 0.0249) in the patients. The APACHE II scores correlated with the numbers of CD14+CD163+CD115+ (R = 0.4581, P = 0.0244) monocytes and the levels of plasma IL-10 (R = 0.4178, P = 0.0422) in the MAP patients. However, there was no significant association among other measures tested in this population.

CONCLUSION

Increased numbers of CD14+CD163- and CD14+ CD163-MAC387+ monocytes may contribute to the pathogenesis of MAP, and increased numbers of CD14+CD163+CD115+ monocytes may be a biomarker for evaluating the severity of MAP.

B cell regulation of the anti-tumor response and role in carcinogenesis

The balance between immune effector cells such as T cells and natural killer cells, and immunosuppressive Treg cells, dendritic, myeloid and monocytic sub-populations in the tumor microenvironment acts to calibrate the immune response to malignant cells. Accumulating evidence is pointing to a role for B cells in modulating the immune response to both solid tumors and hematologic cancer. Evidence from murine autoimmune models has defined B regulatory cell (Breg) subsets that express cytokines such as IL-10, TGF-β, and/or express immune regulatory ligands such as PD-L1, which can suppress T cell and/or natural killer cell responses. Multiple murine tumor models exhibit decreased tumor growth in B cell deficient or B cell depleted mice. In several of these models, B cells inhibit T cell mediated tumor immunity and/or facilitate conversion of T cells to CD4⁺CD25⁺FoxP3⁺ T regs, which act to attenuate the innate and/or adaptive antitumor immune response.

Mechanisms of suppression include the acquisition of inhibitory ligand expression, and phosphorylation of Stat3, and induction of IL-10 and TGF-β, resulting in a Breg phenotype. Breg suppressive activity may affect diverse cell subtypes, including T effector cells, NK cells, myeloid derived suppressor cells (MDSC) and/or tumor associated macrophages. B cells may also directly promote tumorigenesis through recruitment of inflammatory cells, and upregulation of pro-angiogenic genes and pro-metastatic collagenases.

Breg infiltration has now been identified in a variety of solid tumor malignancies including but not limited to ovarian, gastric, non-small cell lung cancer, pancreatic, esophageal, head and neck, and hepatocellular carcinomas. Increasing evidence suggests that recruitment of B cells and acquisition of suppressive activity within the tumor bed may be an important mechanism through which B cells may modulate innate and/or adaptive anti-tumor immunity. B cell depletion in the clinic using anti-CD20 antibodies and/or inhibitors of BTK and/or other signaling pathways, may be a useful strategy for augmenting the anti-tumor immune response.