Malignant pleural effusion (MPE) is the lethal consequence of various human cancers metastatic to the pleural cavity. However, the mechanisms responsible for the development of MPE are still obscure. Here we show that mutant KRAS is important for MPE induction in mice. Pleural disseminated, mutant KRAS bearing tumour cells upregulate and systemically release chemokine ligand 2 (CCL2) into the bloodstream to mobilize myeloid cells from the host bone marrow to the pleural space via the spleen. These cells promote MPE formation, as indicated by splenectomy and splenocyte restoration experiments. In addition, KRAS mutations are frequently detected in human MPE and cell lines isolated thereof, but are often lost during automated analyses, as indicated by manual versus automated examination of Sanger sequencing traces. Finally, the novel KRAS inhibitor deltarasin and a monoclonal antibody directed against CCL2 are equally effective against an experimental mouse model of MPE, a result that holds promise for future efficient therapies against the human condition.

Atopic dermatitis (AD) and psoriasis are common skin diseases with a high negative impact on patients' quality of life. Both diseases are mediated by a pro‐inflammatory infiltrate consisting of several cell types, such as T‐cells, antigen‐presenting cells and granulocytes and display disturbed keratinocyte differentiation. Given the fact that histamine levels are also highly elevated in inflamed skin, it is likely that histamine plays a relevant role in disease pathology. However, antagonists blocking histamine H1 receptor or H2 receptors are largely ineffective in reducing chronic symptoms in AD and psoriasis. Over the last years, much research has been undertaken to shed light into the mode of action of the most recently discovered histamine H4 receptor. This research has shown that H4 receptor antagonists display antipruritic and anti‐inflammatory effects not only in mouse models but also in first human clinical trials, and therefore, H4 receptors might present a novel therapeutic target. In this review, we summarize the effects of the H4 receptors on different cell types, mouse models and clinical studies in regard to AD and psoriasis respectively. Linked Articles This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc

Regulatory T cells (Tregs) are critical for the maintenance of immune homeostasis and self-tolerance and can be therapeutically used for prevention of unwanted immune responses such as allotransplant rejection. Tregs are characterized by expression of the transcription factor Foxp3, and recent work suggests that epigenetic imprinting of Foxp3 and other Treg-specific epigenetic signatures genes is crucial for the stabilization of both Foxp3 expression and immunosuppressive properties within Tregs. Lately, vitamin C was reported to enhance the activity of enzymes of the ten-eleven translocation family, thereby fostering the demethylation of Foxp3 and other Treg-specific epigenetic signatures genes in developing Tregs. Here, we in vitro generated alloantigen-induced Foxp3+ Tregs (allo-iTregs) in presence of vitamin C. Although vitamin C hardly influenced the transcriptome of allo-iTregs as revealed by RNA-seq, those vitamin C-treated allo-iTregs showed a more pronounced demethylation of Foxp3 and other Treg-specific epigenetic signatures genes accompanied with an enhanced stability of Foxp3 expression. Accordingly, when being tested in vivo in an allogeneic skin transplantation model, vitamin C-treated allo-iTregs showed a superior suppressive capacity. Together, our results pave the way for the establishment of novel protocols for the in vitro generation of alloantigen-induced Foxp3+ Tregs for therapeutic use in transplantation medicine.

Regulatory T cells (Tregs) are potential immunotherapeutic candidates to induce transplantation tolerance. However, stability of Tregs still remains contentious and may potentially restrict their clinical use. Recent work suggested that epigenetic imprinting of Foxp3 and other Treg-specific signature genes is crucial for stabilization of immunosuppressive properties of Foxp3+ Tregs, and that these events are initiated already during early stages of thymic Treg development. However, the mechanisms governing this process remain largely unknown. Here we demonstrate that thymic antigen-presenting cells (APCs), including thymic dendritic cells (t-DCs) and medullary thymic epithelial cells (mTECs), can induce a more pronounced demethylation of Foxp3 and other Treg-specific epigenetic signature genes in developing Tregs when compared to splenic DCs (sp-DCs). Transcriptomic profiling of APCs revealed differential expression of secreted factors and costimulatory molecules, however neither addition of conditioned media nor interference with costimulatory signals affected Foxp3 induction by thymic APCs in vitro. Importantly, when tested in vivo both mTEC- and t-DC-generated alloantigen-specific Tregs displayed significantly higher efficacy in prolonging skin allograft acceptance when compared to Tregs generated by sp-DCs. Our results draw attention to unique properties of thymic APCs in initiating commitment towards stable and functional Tregs, a finding that could be highly beneficial in clinical immunotherapy.

The vast majority of Foxp3 + regulatory T cells (Tregs) are generated in the thymus, and several factors such as cytokines and unique thymic antigen-presenting cells are known to contribute to the development of these thymus-derived Tregs (tTregs). Here, we report the existence of a specific subset of Foxp3 + Tregs within the thymus, characterised by the expression of IL-1R2, a decoy receptor for the inflammatory cytokine IL-1. Detailed flow cytometric analysis of thymocytes from Foxp3 hCD2 xRAG1 GFP reporter mice revealed that IL-1R2 + Tregs are mainly RAG1 GFPand CCR6 + CCR7-, demonstrating that these Tregs are recirculating cells entering the thymus from the periphery and display an activated phenotype. In the spleen, the majority of IL-1R2 + Tregs express neuropilin-1 (Nrp-1) and Helios, suggesting a thymic origin of these Tregs. Interestingly, among all tissues studied the highest frequency of IL-1R2 + Tregs was observed in the thymus, indicating a preferential recruitment of this Treg subset back to the thymus. Using fetal thymic organ cultures (FTOCs), we could demonstrate that increased concentrations of exogenous IL-1 cause a block of intrathymic Treg development, resulting in decreased frequencies of CD25 + Foxp3 + tTregs and an accumulation of CD25 + Foxp3-Treg precursors. Interestingly, addition of IL-1R2 + , but not IL-1R2-Tregs to reaggregated thymic organ cultures (RTOCs) could abrogate this IL-1-mediated block, demonstrating that recirculating IL-1R2 + Tregs can quench IL-1 signals in the thymus and thereby maintain thymic Treg development even under inflammatory conditions.

is overexpressed in patients with atopic dermatitis and modulates T-cell proliferative responses by targeting cytotoxic T lymphocyte-associated antigen 4. J

In the last two decades, the exponential progress in the field of genetics could reveal the genetic impact on the onset and progression of several diseases affecting the immune system. This knowledge has led to the discovery of more than 400 monogenic germline mutations, also known as “inborn errors of immunity (IEI)”. Given the rarity of various IEI and the clinical diversity as well as the limited available patients’ material, the continuous development of novel cell-based in vitro models to elucidate the cellular and molecular mechanisms involved in the pathogenesis of these diseases is imperative. Focusing on stem cell technologies, this review aims to provide an overview of the current available in vitro models used to study IEI and which could lay the foundation for new therapeutic approaches. We elaborate in particular on the use of induced pluripotent stem cell-based systems and their broad application in studying IEI by establishing also novel infection culture models. The review will critically discuss the current limitations or gaps in the field of stem cell technology as well as the future perspectives from the use of these cell culture systems.