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Interleukin-10 (IL-10) promotes the formation and development of malignant pleural effusion (MPE). Previous studies have elucidated the pathogenesis from the view of the immune-regulation function of CD4 + T-cells. However, the underlying mechanism is still not fully understood. In this study, our results showed that IL-10 deficiency reduced the percentage of macrophages in mouse MPE and regulated M1/M2 polarization in vivo and in vitro . The migration capacity of tumor cells was suppressed, and apoptosis was promoted when tumor cells were cocultured with MPE macrophages in the absence of IL-10. Messenger RNA sequencing of MPE macrophages showed that S100A9 was downregulated in IL-10 -/- mice. Bone marrow-derived macrophages obtained from wild-type mice transfected with S100A9-specific small interfering RNAs (siRNAs) also showed less M2 and more M1 polarization than those from the siRNA control group. Furthermore, downregulation of S100A9 using S100A9-specific siRNA suppressed MPE development, decreased macrophages, and modulated macrophage polarization in MPE in vivo . In conclusion, S100A9 plays a vital role in the process of IL-10 deficiency-mediated MPE suppression by regulating M1/M2 polarization, thus influencing the tumor-migration capacity and apoptosis. This could result in clinically applicable strategies to inhibit the formation of MPE by regulating the polarization of MPE macrophages., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2023 Xue-Bin Pei et al.)

Background: Lung cancer is the second most commonly diagnosed cancer and the leading cause of cancer-related death. Malignant pleural effusion (MPE) is a special microenvironment for lung cancer metastasis. Alternative splicing, which is regulated by splicing factors, affects the expression of most genes and influences carcinogenesis and metastasis., Methods: mRNA-seq data and alternative splicing events in lung adenocarcinoma (LUAD) were obtained from The Cancer Genome Atlas (TCGA). A risk model was generated by Cox regression analyses and LASSO regression. Cell isolation and flow cytometry were used to identify B cells., Results: We systematically analyzed the splicing factors, alternative splicing events, clinical characteristics, and immunologic features of LUAD in the TCGA cohort. A risk signature based on 23 alternative splicing events was established and identified as an independent prognosis factor in LUAD. Among all patients, the risk signature showed a better prognostic value in metastatic patients. By single-sample gene set enrichment analysis, we found that among tumor-infiltrating lymphocytes, B cells were most significantly correlated to the risk score. Furthermore, we investigated the classification and function of B cells in MPE, a metastatic microenvironment of LUAD, and found that regulatory B cells might participate in the regulation of the immune microenvironment of MPE through antigen presentation and promotion of regulatory T cell differentiation., Conclusions: We evaluated the prognostic value of alternative splicing events in LUAD and metastatic LUAD. We found that regulatory B cells had the function of antigen presentation, inhibited naïve T cells from differentiating into Th1 cells, and promoted Treg differentiation in LUAD patients with MPE., Competing Interests: The authors have declared that no conflict of interest exists., (Copyright: © 2023 Shao et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Accurate differential diagnosis is the key to choosing the correct treatment for pleural effusion. The present study aimed to assess whether interleukin 32 (IL-32) could be a new biomarker of tuberculous pleural effusion (TPE) and to explore the biological role of IL-32 in TPE. IL-32 levels were evaluated in the pleural effusions of 131 patients with undetermined pleural effusion from Wuhan and Beijing cohorts using an enzyme-linked immunosorbent assay method. Macrophages from TPE patients were transfected with IL-32-specific small interfering RNA (siRNA), and adenosine deaminase (ADA) expression was determined by real-time PCR and colorimetric methods. With a cutoff value of 247.9 ng/mL, the area under the curve of the receiver operating characteristic (ROC) curve for IL-32 was 0.933 for TPE, and the sensitivity and specificity were 88.4% and 93.4%, respectively. A multivariate logistic regression model with relatively good diagnostic performance was established. IL-32-specific siRNA downregulated ADA expression in macrophages, and IL-32γ treatment significantly induced ADA expression. Our results indicate that IL-32 in pleural effusion may be a novel biomarker for identifying patients with TPE. In addition, our multivariate model is acceptable to rule in or rule out TPE across diverse prevalence settings. Furthermore, IL-32 may modulate ADA expression in the tuberculosis microenvironment. (This study has been registered at ChiCTR under registration number ChiCTR2100051112 [https://www.chictr.org.cn/index.aspx].) IMPORTANCE Tuberculous pleural effusion (TPE) is a common form of extrapulmonary tuberculosis, with manifestations ranging from benign effusion with spontaneous absorption to effusion with pleural thickening, empyema, and even fibrosis, which can lead to a lasting impairment of lung function. Therefore, it is of great significance to find a rapid method to establish early diagnosis and apply antituberculosis therapy in the early stage. This study indicates that interleukin 32 (IL-32) in pleural effusion is a new high-potency marker to distinguish TPE from pleural effusions with other etiologies. A multivariate model combining age, adenosine deaminase (ADA), lactic dehydrogenase, and IL-32 may reliably rule in TPE in intermediate- or high-prevalence areas. Additionally, we observed that IL-32 might regulate ADA expression in macrophages in the tuberculosis microenvironment. Therefore, this study provides new insights into the role of IL-32 in the tuberculosis microenvironment.

Background: Malignant pleural mesothelioma (MPM) is one of the most aggressive tumors with few effective treatments worldwide. It has been suggested that alternative splicing at the transcriptome level plays an indispensable role in MPM., Methods: We analyzed the splicing profile of 84 MPM patients from the TCGA cohort by using seven typical splicing types. We classified MPM patients based on their splicing status and conducted a comprehensive analysis of the correlation between the splicing classification and clinical characteristics, genetic variation, pathway changes, immune heterogeneity, and potential therapeutic targets., Results: The expression of the alternative splicing regulator SRPK1 is significantly higher in MPM tissues than in normal tissues, and correlates with poor survival. SRPK1 deficiency promotes MPM cell apoptosis and inhibits cell migration in vitro. We divided the MPM patients into four clusters based on their splicing profile and identified two clusters associated with the shortest (cluster 3) and longest (cluster 4) survival time. We present the different gene signatures of each cluster that are related to survival and splicing. Comprehensive analysis of data from the GDSC and TCGA databases revealed that cluster 3 MPM patients could respond well to the small-molecule inhibitor CHIR-99021, a small-molecule inhibitor of GSK-3., Conclusion: We performed unsupervised clustering of alternative splicing data from 84 MPM patients from the TCGA database and identified a cluster associated with the worst prognosis that was sensitive to a GSK-3 inhibitor., (© 2022 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.)

Abnormal function of immune cells is one of the key mechanisms leading to severe clinical symptoms in coronavirus disease 2019 patients, and metabolic pathways can destroy the function of the immune system by affecting innate and adaptive immune responses. However, the metabolic characteristics of the immune cells of the SARS-CoV-2 infected organs in situ remaining elusive. We reanalyzed the metabolic-related gene profiles in single-cell RNA sequencing data, drew the metabolic landscape in bronchoalveolar lavage fluid immune cells, and elucidated the metabolic remodeling mechanism that might lead to the progression of COVID-19 and the cytokine storm. Enhanced glycolysis is the most important common metabolic feature of all immune cells in COVID-19 patients. CCL2 + T cells, Group 2 macrophages with high SPP1 expression and myeloid dendritic cells are among the main contributors to the cytokine storm produced by infected lung tissue. Two metabolic analysis methods, including Compass, showed that glycolysis, fatty acid metabolism, bile acid synthesis and purine and pyrimidine metabolism levels of CCL2 + T cells, Group 2 macrophages and myeloid dendritic cells were upregulated and correlated with cytokine storms of COVID-19 patients. This might be the key metabolic regulatory factor for immune cells to produce large quantities of cytokines., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Shao, Shi, Du, Pei, Gu and Yi.)

Characterization of T cell receptor (TCR) repertoires is essential for understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection involving T cell adaptive immunity. The characteristics of TCR sequences and distinctive signatures of T cell subsets in tuberculous patients are still unclear. By combining single-cell TCR sequencing (sc-TCR seq) with single-cell RNA sequencing (sc-RNA seq) and flow cytometry to characterize T cells in tuberculous pleural effusions (TPEs), we identified 41,718 CD3 + T cells in TPEs and paired blood samples, including 30,515 CD4 + T cells and 11,203 CD8 + T cells. Compared with controls, no differences in length and profile of length distribution were observed in complementarity determining region 3 (CDR3) in both CD4 + and CD8 + T cells in TPE. Altered hydrophobicity was demonstrated in CDR3 in CD8 + T cells and a significant imbalance in the TCR usage pattern of T cells with preferential expression of TRBV4-1 in TPE. A significant increase in clonality was observed in TCR repertoires in CD4 + T cells, but not in CD8 + T cells, although both enriched CD4 + and CD8 + T cells showed T H 1 and cytotoxic signatures. Furthermore, we identified a new subset of polyfunctional CD4 + T cells with CD1-restricted, T H 1, and cytotoxic characteristics, and this subset might provide protective immunity against Mtb ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Shao, Yi, Huang, Peng, Wu, Shi and Zhai.)

Objective: Pre-treatment biomarkers to estimate overall survival (OS) for malignant pleural effusion (MPE) are unidentified, especially those in pleural fluid. We evaluated the relationship between OS and total protein-chloride ratio in malignant pleural effusion (PE TPClR)., Materials and Methods: A retrospective study was undertaken to identify patients from 2006 to 2018 who had pathologically or cytologically confirmed MPE and received no tumor-targeted therapy. We recorded the pre-treatment clinicopathologic characteristics and follow-up status. OS was estimated by the Kaplan-Meier method, and the association between variables and OS was evaluated by Cox proportional hazards models., Results: We screened 214 patients who met the eligibility criteria. The optimal cutoff value for the PE TPClR was set at 0.53. The univariate analysis showed that there was a significant correlation between PE TPClR and OS ( P < 0.001). The multivariate analysis between OS and the variables selected from the univariate analysis showed that the levels of neutrophil, alkaline phosphatase, neuron-specific enolase, platelets, albumin in peripheral blood, and white blood cells in pleural effusion were also independent predictors of OS., Conclusion: In patients with MPE, pre-treatment PE TPClR independently predicts OS. Although further research is necessary to generalize our results, this information will help clinicians and patients to determine the most appropriate treatment for MPE patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Qiao, Zhang, Shi and Yi.)

The complex interactions among different immune cells have important functions in the development of malignant pleural effusion (MPE). Here we perform single-cell RNA sequencing on 62,382 cells from MPE patients induced by non-small cell lung cancer to describe the composition, lineage, and functional states of infiltrating immune cells in MPE. Immune cells in MPE display a number of transcriptional signatures enriched for regulatory T cells, B cells, macrophages, and dendritic cells compared to corresponding counterparts in blood. Helper T, cytotoxic T, regulatory T, and T follicular helper cells express multiple immune checkpoints or costimulatory molecules. Cell-cell interaction analysis identifies regulatory B cells with more interactions with CD4 + T cells compared to CD8 + T cells. Macrophages are transcriptionally heterogeneous and conform to M2 polarization characteristics. In addition, immune cells in MPE show the general up-regulation of glycolytic pathways associated with the hypoxic microenvironment. These findings show a detailed atlas of immune cells in human MPE and enhance the understanding of potential diagnostic and therapeutic targets in advanced non-small cell lung cancer., (© 2021. The Author(s).)

Background and Objective: The accurate differential diagnosis of tuberculous pleural effusion (TPE) from other exudative pleural effusions is often challenging. We aimed to validate the accuracy of complement component C1q in pleural fluid (PF) in diagnosing TPE. Methods: The level of C1q protein in the PF from 49 patients with TPE and 61 patients with non-tuberculous pleural effusion (non-TPE) was quantified by enzyme-linked immunosorbent assay, and the diagnostic performance was assessed by receiver operating characteristic (ROC) curves based on the age and gender of the patients. Results: The statistics showed that C1q could accurately diagnose TPE. Regardless of age and gender, with a cutoff of 6,883.9 ng/mL, the area under the curve (AUC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of C1q for discriminating TPE were 0.898 (95% confidence interval: 0.825-0.947), 91.8 (80.4-97.7), 80.3 (68.2-89.4), 78.9 (69.2-86.2), and 92.5 (82.6-96.9), respectively. In subgroup analysis, the greatest diagnostic accuracy was achieved in the younger group (≤ 50 years of age) with an AUC of 0.981 (95% confidence interval: 0.899-0.999) at the cutoff of 6,098.0 ng/mL. The sensitivity, specificity, PLR, NLR, PPV, and NPV of C1q were 95.0 (83.1-99.4), 92.3 (64.0-99.8), 97.4 (85.2-99.6), and 85.7 (60.6-95.9), respectively. Conclusion: Complement component C1q protein was validated by this study to be a promising biomarker for diagnosing TPE with high diagnostic accuracy, especially among younger patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Qiao, Shao, Yi and Shi.)

Background: The detection of interleukin 33 (IL-33) in pleural effusion may be more sensitive in diagnosing tuberculous pleural effusion (TPE). The present study aimed to assess the accuracy of pleural IL-33 for the diagnosis of TPE by means of meta-analysis and systematic review of relevant studies., Method: After retrieving the published studies, the sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and a summary receiver operating characteristic curve were assessed to estimate the usefulness of pleural IL-33 in diagnosing TPE using meta-analysis with a random-effects model. We also performed meta-regression and subgroup analysis., Results: A total of 639 patients from 6 studies were analyzed. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 0.87 (95% confidence interval [CI], 0.82-0.91), 0.76 (95% CI, 0.72-0.80), 6.54 (95% CI, 2.65-16.15), 0.17 (95% CI, 0.10-1.27), and 45.40 (95% CI, 12.83-160.70) respectively. The area under the curve was 0.94. The composition of the included population was the main cause of heterogeneity and subgroup analysis showed that pleural IL-33 had a higher specificity (0.93, 95% CI 0.87-0.96) when used for differential diagnosis between TPE and malignant pleural effusion., Conclusion: The detection of IL-33 alone in pleural effusion seems to not be an efficient diagnostic marker for TPE but may serve as a novel biomarker to differentiate between TPE and malignant pleural effusion., Competing Interests: No potential conflicts of interest relevant to this article were reported. The authors have no conflicts of interest to disclose., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Malignant pleural effusion (MPE) is a frequent complication of advanced malignancies that leads to a poor quality of life and limits treatment options., Objective: The objective of this study was to identify biomarkers of survival in patients with MPE, which will greatly facilitate the clinical management of this complication., Methods: This retrospective study recruited patients who had been pathologically diagnosed with MPE, regardless of the type of primary cancer, at Beijing Chao-Yang Hospital over 158 months. Demographic, clinical, hematological, and pleural fluid data were collected and analyzed as potential predictors of survival, and a new predictive model was developed based on Cox and logistic regression analyses., Results: In our alternative prognostic model (n = 281), four routinely detected variables, namely, carcinoembryonic antigen (CEA) level, monocyte count, N-terminal pro B-type natriuretic peptide (NT-pro-BNP) level, and pleural effusion chloride level on admission, were identified as predictors (the CONCH prognostic score). Patients were divided into three prognosis subgroups based on risk stratification, with median survival periods of 17, 11, and 5 months, respectively. In comparison with the low-risk group, patients in the medium- and high-risk groups showed significantly poorer survival (medium-risk group: hazard ratio [HR], 1.586; 95% confidence interval [CI], 1.047-2.402; P = 0.029; high-risk group: HR, 4.389; 95% CI, 2.432-7.921; P < 0.001)., Conclusion: Four routinely detected variables were used to develop the CONCH scoring system, which was confirmed to be an accurate prognostic score for patients with MPE. This system can guide the selection of interventions and management for MPE., Competing Interests: The authors have no financial or other conflicts of interest., (© 2021 Zhang et al.)

Malignant pleural effusion (MPE) is a frequent complication of malignancies and poses a clinical problem. CD4 + T lymphocytes are the most frequent cell population in MPE. Traditionally, CD4 + T cells are classified into two subsets based on cytokine production profiles, type 1 (Th1) and type 2 (Th2) helper T cells, which exhibit distinct functions. Recently, other T-cell subsets have been added to the Th-cell "portfolio", including regulatory T, Th17, Th9, and Th22 cells. The current review focuses on summarizing the Th-cell phenotypic characteristics, mechanism of Th-cell differentiation, and their pleural space recruitment, based on recent research. We also describe the interplay in MPE among different Th cells, as well as Th cells and lung cancer cells or mesothelial cells. Future research should expand the landscape map of human MPE immune cells, explore the immuno-regulation of B cells, and investigate the communication between macrophages and Th cells in MPE, which may facilitate meaningful advancements in the diagnoses and therapeutics of MPE., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Emerging evidence indicates that Myo9b is a cancer metastasis-related protein and functions in a variety of immune-related diseases. However, it is not clear whether and how Myo9b functions in malignant pleural effusion (MPE). In this study, our data showed that Myo9b expression levels correlated with lung cancer pleural metastasis, and nucleated cells in MPE from either patients or mice expressed a lower level of Myo9b than those in the corresponding blood. Myo9b deficiency in cancer cells suppressed MPE development via inhibition of migration. Myo9b deficiency in mice suppressed MPE development by decreasing T H 1 cells and increasing T H 17 cells. CD4 + naive T cells isolated from Myo9b -/- mouse spleens exhibited less T H 1 cell differentiation and more T H 17 cell differentiation in vitro. mRNA sequencing of nucleated cells showed that T cell-specific adaptor protein (TSAd) was downregulated in Myo9b -/- mouse MPE, and enrichment of the H3K27me3 mark in the TSAd promoter region was found in the Myo9b -/- group. Naive T cells purified from wild type mouse spleens transfected with TSAd-specific small interfering RNAs (siRNAs) also showed less T H 1 cell differentiation and more T H 17 cell differentiation than those from the siRNA control group. Furthermore, downregulation of TSAd in mice using cholesterol-conjugated TSAd-specific siRNA suppressed MPE development, decreased T H 1 cells, and increased T H 17 cells in MPE in vivo. Taken together, Myo9b deficiency suppresses MPE development not only by suppressing pleural cancer metastasis but also by regulating T H 1/T H 17 cell response via a TSAd-dependent pathway. This work suggests Myo9b and TSAd as novel candidates for future basic and clinical investigations of cancer., (Copyright © 2020 by The American Association of Immunologists, Inc.)

IL-10, produced by a wide variety of cells, is a highly pleiotropic cytokine that plays a critical role in the control of immune responses. However, its regulatory activity in tumor immunity remains poorly understood. In this study, we report that IL-10 deficiency robustly suppressed the formation of malignant pleural effusion (MPE) and significantly enhanced miR-7116-5p expression in pleural CD4 + T cells. We demonstrated that miR-7116-5p suppressed IL-10-mediated MPE formation by inhibiting pleural vascular permeability as well as tumor angiogenesis and tumor growth. IL-10 promoted MPE formation by suppressing miR-7116-5p that enhances T H 1 response. We identified G protein-coupled receptor 55 (GPR55) as a potential target of miR-7116-5p, and miR-7116-5p promoted T H 1 cell function by downregulating GPR55. Moreover, GPR55 promoted MPE formation by inhibiting T H 1 cell expansion through the ERK phosphorylation pathway. These results uncover an IL-10-mediated pathway controlling T H 1 cells and demonstrate a central role for miR-7116-5p/GPR55/ERK signaling in the physiological regulation of IL-10-driven pro-malignant responses., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Background: The objective of our study was to analyze the prognostic value of the combination of serum ALP and pleural effusion LDH (AL score) for malignant pleural effusion (MPE) patients., Methods: This study includes retrospective, descriptive and observational research from 1 June 2006 to 1 December 2017, which aimed to identify prognostic factors related to MPE patients. We analyzed the association of various clinical features, routinely tested markers from peripheral blood and MPE at diagnosis and overall survival (OS). All MPE patients were assigned to three groups according to their AL score. The impact of the AL score and other prognostic factors were evaluated with multivariable regression., Results: According to their AL score, 193 patients were assigned to three groups with 25 in group 0 (sALP < 65 U/L and pLDH < 155 U/L), 121 in group 1 (sALP > 65 U/L or pLDH > 155 U/L) and 47 (sALP > 65 U/L and pLDH > 155 U/L) in group 2. For groups 0, 1 and 2, median survival times (MST) were 23, 15 and 7 months, respectively. Among the three groups, MST, serum albumin level, C reactive protein, erythrocyte sedimentation rate, the ratios of platelet-to-lymphocyte, neutrophil-to-lymphocyte showed significant differences. The counts of neutrophils, monocytes, platelets and AL score (0 vs. 1, P = 0.038, hazard ratio [HR]: 1.858, 95% confidence interval [CI]: [1.034, 3.339]; 0 vs. 2, P = 0.001, HR: 2.993, 95% CI: [1.556, 5.531]) were independent prognostic indicators for OS of MPE patients., Conclusion: AL score is a promising indicator which can be used to predict the prognosis of MPE patients. It can assist physicians in the selection of patients for appropriate palliative treatment., Key Points: To our knowledge, this paper is the first study that combined two enzymes (sALP and pLDH) from serum and pleural effusion and studied the prognostic value for MPE patients. It has been proved to be a promising indicator to assist physicians select patients for appropriate palliative treatment., (© 2019 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.)

Background: Pleural effusions are common complications of various diseases. Patients with malignant pleural effusion (MPE) usually face poor prognosis and short life expectancy. Discriminating between MPE and benign pleural effusion remains to be difficult. The aim of our current study was to evaluate whether CD206 + CD14 + macrophages could be a diagnostic biomarker for MPE., Methods: The percentages of CD14 + , CD86 + CD14 + and CD206 + CD14 + macrophages in pleural effusions were determined by flow cytometry in 34 patients with MPE and 26 with benign pleural effusion, and their diagnostic performances were evaluated by receiver operating characteristic (ROC) curves., Results: The percentages of CD14 + , CD86 + CD14 + and CD206 + CD14 + macrophages were remarkably higher in MPE than in benign pleural effusion (all P<0.05). With a cutoff value of 39.8%, a high sensitivity of 88.2% and high specificity of 100.0% were found in CD206 + CD14 + macrophages to diagnose MPE. The area under the curve, positive predictive value and negative predictive value of CD206 + CD14 + macrophages were 0.980 (95% CI, 0.905 to 0.999), 100.0 (88.4 to 100.0) and 86.7 (69.3 to 96.2), respectively. The diagnostic performance of CD206 + CD14 + macrophages was more accurate than those of CD14 + and CD86 + CD14 + macrophages., Conclusions: CD206 + CD14 + macrophages could be used to discriminate MPE from benign pleural effusion., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare.

The role of IL-10 in malignant pleural effusion (MPE) remains unknown. By using murine MPE models, we observed that an increase in pleural IL-10 was a significant predictor of increased risk of death. We noted that T H 1- and T H 17-cell content in MPE was higher in IL-10 -/- mice than in WT mice, and IL-10 deficiency promoted differentiation into T H 1 but not into T H 17 cells. A higher fraction of T H 1 and T H 17 cells in the MPE of IL-10 -/- mice expressed CXCR3 compared with WT mice. We also demonstrated that Lewis lung cancer and colon adenocarcinoma cells secreted large amounts of CXCL10, a ligand of CXCR3, which induced the migration of T H 1 and T H 17 cells into the MPE, and IFN-γ could promote this signaling cascade. Furthermore, intrapleural injection of mice with CXCL10-deficient tumor cells led to decreased T H 1- and T H 17-cell content in MPE, increased MPE volume, and reduced survival of MPE-bearing mice. Taken together, we demonstrated that IL-10 deficiency promoted T-cell differentiation into T H 1 cells and upregulated the CXCR3-CXCL10 signaling pathway that recruits T H 1 and T H 17 cells into MPE, ultimately resulting in decreased MPE formation and longer survival time of mice-bearing MPE., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Inflammatory signaling networks between tumor cells and immune cells contribute to the development of malignant pleural effusion (MPE). B cells have been found in MPE; however, little is known about their roles there. In the present study, by using mouse MPE models, we noted that although the total B cells in MPE were decreased as compared with the corresponding blood and spleen, the percentage of activated naïve B cells expressing higher levels of CD80, CD86, myosin heavy chain-II, CD44, CD69, and programmed cell death-ligand 1 (PD-L1) molecules were increased in wild-type mouse MPE. Compared with wild-type mice, decreased T helper (T H )1 cells and increased T H 17 cells were present in B cell-deficient mouse MPE, which paralleled to the reduced MPE volume and longer survival time. Adoptive transfer of activated naïve B cells into B cell-deficient mice was able to increase T H 1 cells and decrease T H 17 cells in MPE and shorten the survival of mice bearing MPE. Furthermore, we demonstrated that activated naïve B cells inhibited T H 17-cell expansion via the PD-1/PD-L1 pathway and promoted naïve CD4 + T-cell differentiation into T H 1/T H 17 cells through secreting IL-27/IL-6 independent of the PD-1/PD-L1 pathway. Collectively, our data uncovered a mechanism by which naïve B cells promote MPE formation by regulating T H 1/T H 17 cell responses, making these B cells an attractive target for therapeutic intervention in the fight against cancer.