The chemokine receptor CCR2 maintains plasmacytoid dendritic cell homeostasis

GLS and GOT2 as prognostic biomarkers associated with dendritic cell and immunotherapy response in breast cancer

Breast cancer is the females' most common cancer. Targeting the immune microenvironment is a new and promising treatment method for breast cancer. Nevertheless, only a small section of patients can profit by immunotherapy, and improving the ability to accurately predict the potential for immunotherapy response is still awaiting further exploration. In this study, we found that the key factors of glutamine metabolism, glutaminase 1 (GLS) and mitochondrial aspartate transaminase (GOT2), showed opposite expression patterns in breast cancer samples. Based on the expression level of GLS and GOT2, we divided the breast cancer samples into two clusters: Cluster 2 showed GLS expressed higher and GOT2 expressed lower, whereas Cluster 1 showed GOT2 expressed higher and GLS expressed lower. GSEA showed that the clusters were related to pathways of immunity. Further analysis showed that Cluster 2 was positively associated with immunity infiltration. Through WGCNA, we identified a module strongly correlated with glutamine metabolism and immunity and identified 11 dendritic cell-associated genes involved in dendritic cell development, maturation, activation and other functions. In addition, Cluster 2 also showed higher immune checkpoint gene expression, which suggest the Cluster 2 had even better response to immunotherapy. The validation dataset could also be clustered into two groups. Cluster 2 (GLS expressed higher and GOT2 expressed lower) of the validation dataset was also positively associated with dendritic cells and a better immunotherapy response. Thus, these data indicate that GLS and GOT2 are prognostic biomarkers which closely related to dendritic cells and better reacted to immunotherapy in breast cancer.

Human dendritic cell subsets in the glioblastoma-associated microenvironment

Glioblastoma (GBM) is the most aggressive type of glioma (Grade IV). The presence of cytotoxic T lymphocyte (CTLs) has been associated with improved outcomes in patients with GBM, and it is believed that the activation of CTLs by dendritic cells may play a critical role in controlling the growth of GBM. DCs are professional antigen-presenting cells (APC) that orchestrate innate and adaptive anti-GBM immunity. DCs can subsequently differentiate into plasmacytoid DCs (pDC), conventional DC1 (cDC1), conventional (cDC2), and monocyte-derived DCs (moDC) depending on environmental exposure. The different subsets of DCs exhibit varying functional capabilities in antigen presentation and T cell activation in producing an antitumor response. In this review, we focus on recent studies describing the phenotypic and functional characteristics of DC subsets in humans and their respective antitumor immunity and immunotolerance roles in the GBM-associated microenvironment. The critical components of crosstalk between DC subsets that contribute significantly to GBM-specific immune responses are also highlighted in this review with reference to the latest literature. Since DCs could be prime targets for therapeutic intervention, it is worth summarizing the relevance of DC subsets with respect to GBM-associated immunologic tolerance and their therapeutic potential.

Instructive Cues of Thymic T Cell Selection

A high diversity of αβ T cell receptors (TCRs), capable of recognizing virtually any pathogen but also self-antigens, is generated during T cell development in the thymus. Nevertheless, a strict developmental program supports the selection of a self-tolerant T cell repertoire capable of responding to foreign antigens. The steps of T cell selection are controlled by cortical and medullary stromal niches, mainly composed of thymic epithelial cells and dendritic cells. The integration of important cues provided by these specialized niches, including (a) the TCR signal strength induced by the recognition of self-peptide-MHC complexes, (b) costimulatory signals, and (c) cytokine signals, critically controls T cell repertoire selection. This review discusses our current understanding of the signals that coordinate positive selection, negative selection, and agonist selection of Foxp3⁺ regulatory T cells. It also highlights recent advances that have unraveled the functional diversity of thymic antigen-presenting cell subsets implicated in T cell selection.

The murine DCs transfected with DNA-plasmid encoding CCR9 demonstrate the increased migration to CCL25 and thymic cells in vitro and to the thymus in vivo

BACKGROUND

B220+CD11c+plasmacytoid DCs(pDCs) are known to participate in the negative selection and central tolerance induction by the capturing of self-antigens in peripheral tissues and further migration to the thymus using the CCL25-CCR9 chemotaxis axis.

AIM

Here we investigate the possibility of DCs migration stimulation to the thymus by the transfection with plasmid DNA-constructs encoding CCR9(pmaxCCR9) to develop a system for desired antigen delivery to the thymus for central tolerance induction.

METHODS

Dendritic cells(DCs) cultures were generated from UBC-GFP mice bone marrow cells expressing green fluorescent protein using the rmFlt3-L. DCs cultures were transfected with pmaxCCR9 by electroporation. The efficiency of electroporation was confirmed by RT-qPCR and flow cytometry. The migration of electroporated DCs was assessed in vitro and in vivo.

RESULTS

Dendritic cells(DCs) cultures obtained from UBC-GFP mice contained both B220+pDCs and SIRPa+cDC2. According to the RT-qPCR assay, the electroporation of obtained DCs cultures with pmaxCCR9 resulted in a 94.4-fold increase of RNA encoding CCR9 compared with non-electroporated cultures. Flow cytometry data showed that DCs cultures electroporated with pmaxCCR9 contained a significantly higher frequency of DCs carrying significantly higher levels of surface CCR9. Migration dynamics of obtained DCs analyzed in vitro showed that pmaxCCR9 electroporated DCs migrated significantly more active to CCL25 and thymic cells than non-electroporated and mock-electroporated DCs. In vivo, 30 days after injection, the relative amount of the DCs electroporated with pmaxCCR9 and pmaxMHC encoding antigenic determinants in the mice thymuses was 2.02-fold higher than the relative amount of the DCs electroporated with control plasmid.

CONCLUSION

Thus, the electroporation of murine DCs with pmaxCCR9 stimulated its migration to CCL25 and thymic cells in vitro as well as to the thymus in vivo. The obtained DCs loaded with a desired antigen may be suggested for further evaluation of central tolerance induction ability in in vivo models of autoimmune diseases and transplantation.

Predictive value of plasmacytoid dendritic cells and Toll-like receptor-9 regarding the treatment efficacy of interferon-α in HBeAg-positive chronic hepatitis B patients

Hepatitis B virus (HBV) infection represents a public health threat and a challenge for the medical community. Untimely treatment may lead to liver cirrhosis and even liver cancer. At present, the major treatment for hepatitis B e antigen (HBeAg)-positive chronic hepatitis B patients includes administration of interferon-α (IFN-α), which has anti-viral and immunomodulatory effects. Plasmacytoid dendritic cells (pDCs) and Toll-like receptor-9 (TLR-9) have important roles in anti-viral therapy. However, their predictive value regarding the efficacy of IFN-α treatment of HBeAg-positive chronic hepatitis B (CHB) patients has remained elusive. A total of 178 patients with CHB and HBeAg-positive status, who had not received any previous anti-HBV treatment, were enrolled in the present study. All patients were treated with IFN-α. HBV DNA load, hepatitis B surface antigen and serum alanine aminotransferase were measured prior to and following 48 weeks of treatment. According to HBV levels, the patients were divided into a response group and non-responders group. To determine the amount of pDCs, blood dendritic cell antigen 2 (BDCA-2)- and immunoglobulin-like transcript 7 (ILT7)-expressing cells in liver biopsies were detected using immunohistochemistry. TLR-9 expression in peripheral blood mononuclear cells was determined by reverse transcription-quantitative PCR. There was no significant difference in the proportion of pDCs (BDCA-2; ILT7) and TLR-9 mRNA expression between the response group and the non-responders group prior to IFN-α treatment. After IFN-α treatment, BDCA-2, ILT7 and TLR-9 mRNA expression was obviously increased in the response group compared with that in the non-responders group (P<0.05). Increased expression of BDCA-2, ILT7 and TLR-9 mRNA was negatively correlated with HBV DNA (P<0.05). Increased levels of pDCs and TLR-9 were negatively correlated with HBV DNA, and were thus capable of predicting the IFN-α treatment response in patients with CHB and HBeAg-positive status.

Lymphotoxin α fine-tunes T cell clonal deletion by regulating thymic entry of antigen-presenting cells

Medullary thymic epithelial cells (mTEC) purge the T cell repertoire of autoreactive thymocytes. Although dendritic cells (DC) reinforce this process by transporting innocuous peripheral self-antigens, the mechanisms that control their thymic entry remain unclear. Here we show that mTEC-CD4+ thymocyte crosstalk regulates the thymus homing of SHPS-1+ conventional DCs (cDC), plasmacytoid DCs (pDC) and macrophages. This homing process is controlled by lymphotoxin α (LTα), which negatively regulates CCL2, CCL8 and CCL12 chemokines in mTECs. Consequently, Ltα-deficient mice have increased expression of these chemokines that correlates with augmented classical NF-κB subunits and increased thymic recruitment of cDCs, pDCs and macrophages. This enhanced migration depends mainly on the chemokine receptor CCR2, and increases thymic clonal deletion. Altogether, this study identifies a fine-tuning mechanism of T cell repertoire selection and paves the way for therapeutic interventions to treat autoimmune disorders.