Ligation of dendritic cell-associated lectin-1 induces partial maturation of human monocyte derived dendritic cells

Identification of key genes for atherosclerosis in different arterial beds

Atherosclerosis (AS) is the pathologic basis of various cardiovascular and cerebrovascular events, with a high degree of heterogeneity among different arterial beds. However, mechanistic differences between arterial beds remain unexplored. The aim of this study was to explore key genes and potential mechanistic differences between AS in different arterial beds through bioinformatics analysis. Carotid atherosclerosis (CAS), femoral atherosclerosis (FAS), infrapopliteal atherosclerosis (IPAS), abdominal aortic atherosclerosis (AAS), and AS-specific differentially expressed genes (DEGs) were screened from the GSE100927 and GSE57691 datasets. Immune infiltration analysis was used to identify AS immune cell infiltration differences. Unsupervised cluster analysis of AS samples from different regions based on macrophage polarization gene expression profiles. Weighted gene co-expression network analysis (WGCNA) was performed to identify the most relevant module genes with AS. Hub genes were then screened by LASSO regression, SVM-REF, and single-gene differential analysis, and a nomogram was constructed to predict the risk of AS development. The results showed that differential expression analysis identified 5, 4, 121, and 62 CAS, FAS, IPAS, AAS-specific DEGs, and 42 AS-common DEGs, respectively. Immune infiltration analysis demonstrated that the degree of macrophage and mast cell enrichment differed significantly in different regions of AS. The CAS, FAS, IPAS, and AAS could be distinguished into two different biologically functional and stable molecular clusters based on macrophage polarization gene expression profiles, especially for cardiomyopathy and glycolipid metabolic processes. Hub genes for 6 AS (ADAP2, CSF3R, FABP5, ITGAX, MYOC, and SPP1), 4 IPAS (CLECL1, DIO2, F2RL2, and GUCY1A2), and 3 AAS (RPL21, RPL26, and RPL10A) were obtained based on module gene, gender stratification, machine learning algorithms, and single-gene difference analysis, respectively, and these genes were effective in differentiating between different regions of AS. This study demonstrates that there are similarities and heterogeneities in the pathogenesis of AS between different arterial beds.

T Cell-Mediated Tumor Killing-Related Classification of the Immune Microenvironment and Prognosis Prediction of Lung Adenocarcinoma

BACKGROUND

Although immune checkpoint inhibitors (ICI) are a promising therapeutic strategy for lung adenocarcinoma (LUAD), individual subgroups that might benefit from them are yet to be identified. As T cell-mediated tumor killing (TTK) is an underlying mechanism of ICI, we identified subtypes based on genes associated with TTK sensitivity and assessed their predictive significance for LUAD immunotherapies.

METHODS

Using high-throughput screening techniques, genes regulating the sensitivity of T cell-mediated tumor killing (GSTTK) with differential expression and associations with prognosis were discovered in LUAD. Furthermore, patients with LUAD were divided into subgroups using unsupervised clustering based on GSTTK. Significant differences were observed in the tumor immune microenvironment (TIME), genetic mutation and immunotherapy response across subgroups. Finally, the prognostic significance of a scoring algorithm based on GSTTK was assessed.

RESULTS

A total of 6 out of 641 GSTTK exhibited differential expression in LUAD and were associated with prognosis. Patients were grouped into two categories based on the expression of the six GSTTK, which represented different TTK immune microenvironments in LUAD. Immune cell infiltration, survival difference, somatic mutation, functional enrichment and immunotherapy responses also varied between the two categories. Additionally, a scoring algorithm accurately distinguished overall survival rates across populations.

CONCLUSIONS

TTK had a crucial influence on the development of the varying TIME. Evaluation of the varied TTK modes of different tumors enhanced our understanding of TIME characteristics, wherein the changes in T cell activity in LUAD are reflected. Thus, this study guides the development of more effective therapeutic methods.

Dissecting the process of human neutrophil lineage determination by using alpha-lipoic acid inducing neutrophil deficiency model

Granulocyte-monocyte progenitors (GMPs) differentiate into both neutrophils and monocytes. Recently, uni-potential neutrophil progenitors have been identified both in mice and humans using an array of surface markers. However, how human GMPs commit to neutrophil progenitors and the regulatory mechanisms of fate determination remain incompletely understood. In the present study, we established a human neutrophil deficiency model using the small molecule alpha-lipoic acid. Using this neutrophil deficiency model, we determined that the neutrophil progenitor commitment process from CD371⁺ CD115^– GMPs defined by CD34 and CD15 and discovered that critical signals generated by RNA splicing and rRNA biogenesis regulate the process of early commitment for human early neutrophil progenitors derived from CD371⁺ CD115^– GMPs. These processes were elucidated by single-cell RNA sequencing both in vitro and in vivo derived cells. Sequentially, we identified that the transcription factor ELK1 is essential for human neutrophil lineage commitment using the alpha-lipoic acid (ALA)-inducing neutrophil deficiency model. Finally, we also revealed differential roles for long-ELK1 and short-ELK1, balanced by SF3B1, in the commitment process of neutrophil progenitors. Taken together, we discovered a novel function of ALA in regulating neutrophil lineage specification and identified that the SF3B1-ELK axis regulates the commitment of human neutrophil progenitors from CD371⁺ CD115^– GMPs.

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ALA completely blocks the differentiation of human neutrophils derived from CD34⁺ stem cells in ex-vivo culture.

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CD34 and CD15 could be used to define the early differentiation stages of human neutrophil lineage determination.

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SF3B1-ELK1 signal axis regulates human neutrophil lineage determination.

Crotoxin Isolated from Crotalus durissus terrificus Venom Modulates the Functional Activity of Dendritic Cells via Formyl Peptide Receptors

The Crotalus durissus terrificus rattlesnake venom, its main toxin, crotoxin (CTX), and its crotapotin (CA) and phospholipase A₂ (CB) subunits modulate the immune system. Formyl peptide receptors (FPRs) and lipoxin A₄ (LXA₄) are involved in CTX's effect on macrophages and neutrophils. Dendritic cells (DCs) are plasticity cells involved in the induction of adaptive immunity and tolerance maintenance. Therefore, we evaluated the effect of CTX, CA or CB on the maturation of DCs derived from murine bone marrow (BM). According to data, CTX and CB-but not CA-induced an increase of MHC-II, but not costimulatory molecules on DCs. Furthermore, CTX and CB inhibited the expression of costimulatory and MHC-II molecules, secretion of proinflammatory cytokines and NF-κBp65 and p38/ERK1/2-MAPK signaling pathways by LPS-incubated DCs. Differently, CTX and CB induced IL-10, PGE₂ and LXA₄ secretion in LPS-incubated DCs. Lower proliferation and IL-2 secretion were verified in coculture of CD3⁺ cells and DCs incubated with LPS plus CTX or CB compared with LPS-incubated DCs. The effect of CTX and CB on DCs was abolished in cultures incubated with a FPRs antagonist. Hence, CTX and CB exert a modulation on functional activity of DCs; we also checked the involvement the FPR family on cell activities.

Multiple sclerosis-associated CLEC16A controls HLA class II expression via late endosome biogenesis

C-type lectins are key players in immune regulation by driving distinct functions of antigen-presenting cells. The C-type lectin CLEC16A gene is located at 16p13, a susceptibility locus for several autoimmune diseases, including multiple sclerosis. However, the function of this gene and its potential contribution to these diseases in humans are poorly understood. In this study, we found a strong upregulation of CLEC16A expression in the white matter of multiple sclerosis patients (n = 14) compared to non-demented controls (n = 11), mainly in perivascular leukocyte infiltrates. Moreover, CLEC16A levels were significantly enhanced in peripheral blood mononuclear cells of multiple sclerosis patients (n = 69) versus healthy controls (n = 46). In peripheral blood mononuclear cells, CLEC16A was most abundant in monocyte-derived dendritic cells, in which it strongly co-localized with human leukocyte antigen class II. Treatment of these professional antigen-presenting cells with vitamin D, a key protective environmental factor in multiple sclerosis, downmodulated CLEC16A in parallel with human leukocyte antigen class II. Knockdown of CLEC16A in distinct types of model and primary antigen-presenting cells resulted in severely impaired cytoplasmic distribution and formation of human leucocyte antigen class II-positive late endosomes, as determined by immunofluorescence and electron microscopy. Mechanistically, CLEC16A participated in the molecular machinery of human leukocyte antigen class II-positive late endosome formation and trafficking to perinuclear regions, involving the dynein motor complex. By performing co-immunoprecipitations, we found that CLEC16A directly binds to two critical members of this complex, RILP and the HOPS complex. CLEC16A silencing in antigen-presenting cells disturbed RILP-mediated recruitment of human leukocyte antigen class II-positive late endosomes to perinuclear regions. Together, we identify CLEC16A as a pivotal gene in multiple sclerosis that serves as a direct regulator of the human leukocyte antigen class II pathway in antigen-presenting cells. These findings are a first step in coupling multiple sclerosis-associated genes to the regulation of the strongest genetic factor in multiple sclerosis, human leukocyte antigen class II.

CD244 is expressed on dendritic cells and regulates their functions

Signaling lymphocytic activation molecule (SLAM) receptors have an important role in the development of immune responses because of their roles, for exampe, in NK cell cytotoxicity and cytokine production by NK, T cells and myeloid cells. The SLAM receptor CD244 (2B4, SLAMf4) is expressed on a variety of immune cell types but most of its functions have been examined on NK and T cells. In the present study, we investigated expression and function of CD244 in murine subsets of dendritic cells (DCs). We report that all subsets of murine DCs examined expressed CD244, although the expression levels of CD244 varied between subsets. Splenic and resident mesenteric lymph node (MLN) DCs from CD244(-/-) mice expressed lower levels of CD86 and MHC class II compared with wild-type mice. Upon Toll-like receptor (TLR) stimulation, no differences in surface expression of these molecules were observed between DCs from CD244(-/-) and wild-type mice. However, splenic DCs from CD244(-/-) mice upon stimulation with TLR binding ligands lipopolysaccharide (LPS) and CpG produced significantly higher levels of pro-inflammatory cytokines. In addition, DCs from CD244(-/-) mice elicited increased NK cell activation in vitro. These data add CD244 to a growing list of immuno-modulatory receptors found on DCs.

Statistical colocalization of monocyte gene expression and genetic risk variants for type 1 diabetes

One mechanism by which disease-associated DNA variation can alter disease risk is altering gene expression. However, linkage disequilibrium (LD) between variants, mostly single-nucleotide polymorphisms (SNPs), means it is not sufficient to show that a particular variant associates with both disease and expression, as there could be two distinct causal variants in LD. Here, we describe a formal statistical test of colocalization and apply it to type 1 diabetes (T1D)-associated regions identified mostly through genome-wide association studies and expression quantitative trait loci (eQTLs) discovered in a recently determined large monocyte expression data set from the Gutenberg Health Study (1370 individuals), with confirmation sought in an additional data set from the Cardiogenics Transcriptome Study (558 individuals). We excluded 39 out of 60 overlapping eQTLs in 49 T1D regions from possible colocalization and identified 21 coincident eQTLs, representing 21 genes in 14 distinct T1D regions. Our results reflect the importance of monocyte (and their derivatives, macrophage and dendritic cell) gene expression in human T1D and support the candidacy of several genes as causal factors in autoimmune pancreatic beta-cell destruction, including AFF3, CD226, CLECL1, DEXI, FKRP, PRKD2, RNLS, SMARCE1 and SUOX, in addition to the recently described GPR183 (EBI2) gene.

Signaling by myeloid C-type lectin receptors in immunity and homeostasis

Myeloid cells are key drivers of physiological responses to pathogen invasion or tissue damage. Members of the C-type lectin receptor (CLR) family stand out among the specialized receptors utilized by myeloid cells to orchestrate these responses. CLR ligands include carbohydrate, protein, and lipid components of both pathogens and self, which variably trigger endocytic, phagocytic, proinflammatory, or anti-inflammatory reactions. These varied outcomes rely on a versatile system for CLR signaling that includes tyrosine-based motifs that recruit kinases, phosphatases, or endocytic adaptors as well as nontyrosine-based signals that modulate the activation of other pathways or couple to the uptake machinery. Here, we review the signaling properties of myeloid CLRs and how they impact the role of myeloid cells in innate and adaptive immunity.

Endogenous ligands for C-type lectin receptors: the true regulators of immune homeostasis

C-type lectin receptors (CLRs) have long been known as pattern-recognition receptors implicated in the recognition of pathogens by the innate immune system. However, evidence is accumulating that many CLRs are also able to recognize endogenous 'self' ligands and that this recognition event often plays an important role in immune homeostasis. In the present review, we focus on the human and mouse CLRs for which endogenous ligands have been described. Special attention is given to the signaling events initiated upon recognition of the self ligand and the regulation of glycosylation as a switch modulating CLR recognition, and therefore, immune homeostasis.