RAG-1 and Ly6D independently reflect progression in the B lymphoid lineage

TL1A and IL-18 synergy promotes GM-CSF-dependent thymic granulopoiesis in mice

Acute systemic inflammation critically alters the function of the immune system, often promoting myelopoiesis at the expense of lymphopoiesis. In the thymus, systemic inflammation results in acute thymic atrophy and, consequently, impaired T-lymphopoiesis. The mechanism by which systemic inflammation impacts the thymus beyond suppressing T-cell development is still unclear. Here, we describe how the synergism between TL1A and IL-18 suppresses T-lymphopoiesis to promote thymic myelopoiesis. The protein levels of these two cytokines were elevated in the thymus during viral-induced thymus atrophy infection with murine cytomegalovirus (MCMV) or pneumonia virus of mice (PVM). In vivo administration of TL1A and IL-18 induced acute thymic atrophy, while thymic neutrophils expanded. Fate mapping with Ms4a3-Cre mice demonstrated that thymic neutrophils emerge from thymic granulocyte-monocyte progenitors (GMPs), while Rag1-Cre fate mapping revealed a common developmental path with lymphocytes. These effects could be modeled ex vivo using neonatal thymic organ cultures (NTOCs), where TL1A and IL-18 synergistically enhanced neutrophil production and egress. NOTCH blockade by the LY411575 inhibitor increased the number of neutrophils in the culture, indicating that NOTCH restricted steady-state thymic granulopoiesis. To promote myelopoiesis, TL1A, and IL-18 synergistically increased GM-CSF levels in the NTOC, which was mainly produced by thymic ILC1s. In support, TL1A- and IL-18-induced granulopoiesis was completely prevented in NTOCs derived from Csf2rb-/- mice and by GM-CSFR antibody blockade, revealing that GM-CSF is the essential factor driving thymic granulopoiesis. Taken together, our findings reveal that TL1A and IL-18 synergism induce acute thymus atrophy while  promoting extramedullary thymic granulopoiesis in a NOTCH and GM-CSF-controlled manner.

Vitamin C protects the spleen against PFOA-induced immunotoxicity

Perfluorooctanoic acid (PFOA) is widely used in industrial and consumer products of our daily life. It is well-documented that PFOA is closely associated with fatty liver disease. Recently, cumulating studies demonstrated the immunotoxicity of PFOA, but its harmful effect on the largest immune organ, spleen is still largely unknown. In the present study, we used PFOA-exposed mouse model together with comparative transcriptomic analysis to understand the molecular mechanisms underlying the immunotoxicity of PFOA. Furthermore, we investigated the possible use of vitamin C to reverse the PFOA-induced immunotoxicity in spleen. Our result showed that the PFOA exposure could reduce the spleen weight and plasma lymphocytes, and the splenic comparative transcriptomic analysis highlighted the alteration of cell proliferation, metabolism and immune response through the regulation of gene clusters including nicotinamide nucleotide transhydrogenases (NNT) and lymphocyte antigen 6 family member D and K (LY6D and LY6K). More importantly, the supplementation of vitamin C would relieve the PFOA-reduced spleen index and white blood cells. The bioinformatic analysis of transcriptome suggested its involvement in the spleen cell proliferation and immune response. For the first time, our study delineated the molecular mechanisms underlying the PFOA-induced immunotoxicity in the spleen. Furthermore, our results suggested that the supplementation of vitamin C had beneficial effect on the PFOA-altered spleen functions.

Identification of the Differentiation Stages of Living Cells from the Six Most Immature Murine Hematopoietic Cell Populations by Multivariate Analysis of Single-Cell Raman Spectra

Efforts to expand hematopoietic stem and progenitor cells (HSPCs) in vitro are motivated by their use in the treatment of leukemias and other blood and immune system diseases. The combinations of extrinsic cues within the hematopoietic stem cell (HSC) niche that lead to HSC fate decisions remain unknown. New noninvasive and location-specific techniques are needed to enable identification of the differentiation stages of individual hematopoietic cells on biomaterial microarray screening platforms that minimize the usage of rare HSCs. Here, we show that a combination of Raman microspectroscopy and partial least-squares discriminant analysis (PLS-DA) enables the location-specific identification of individual living cells from the six most immature hematopoietic cell populations, HSC, multipotent progenitor (MPP)-1, MPP-2, MPP-3, common myeloid progenitor, and common lymphoid progenitor. Better than 90% accuracy was achieved. We show that the accuracy of this differentiation stage identification was based on spectral features associated with cell biochemistries. This work establishes that PLS-DA can capture the subtle spectral variations between as many as six closely related cell populations in the presence of potentially significant within-population spectral variation. This noninvasive approach can be used to screen HSC fate decisions elicited by extrinsic cues within biomaterial microarray screening platforms.

Stroma vs epithelium-enhanced prognostics through histologic stratification in pancreatic ductal adenocarcinoma

The mixture of epithelial and stromal components in pancreatic ductal adenocarcinoma (PDAC) may confound sequencing-based studies of tumor gene expression. Virtual microdissection has been suggested as a bioinformatics approach to segment the aforementioned components, and subsequent prognostic gene sets have emerged from this research. We examined the prognostic signature from the epithelial gene set of one such study using laser capture microdissected (LCM) epithelial samples. We also examined this gene set in matched stromal samples to determine whether prognostic findings were specific to the epithelium. LCM samples from 48 long-term and 48 short-term PDAC survivors were obtained. The resultant epithelial and stromal components were subjected to direct mRNA quantification using a 49 gene published PDAC classifier. Component-specific unsupervised hierarchical clustering was used to derive groups and survival differences were quantified. Immunohistochemical validation of particular genes was performed in an independent cohort. Clustering in the epithelial component yielded prognostic differences in univariable analysis (P = .02), but those differences were not significant when controlled for other clinicopathologic covariates (P = .06). Clustering in the stromal component yielded prognostic differences that persisted in the presence of other clinicopathologic covariates (P = .0005). Validation of selected genes in the epithelium (KRT6A-negative prognostic [P = .004]) and stroma (LY6D-improved prognostic [P = .01] and CTSV-negative prognostic [P = .0002]) demonstrated statistical independence in multivariable analysis. Although the genes used in this study were originally identified as being representative of the epithelial component of PDAC, their expression in the stroma appears to provide additional information that may aid in improved prognostication.

The immune response after noise damage in the cochlea is characterized by a heterogeneous mix of adaptive and innate immune cells

Cells of the immune system are present in the adult cochlea and respond to damage caused by noise exposure. However, the types of immune cells involved and their locations within the cochlea are unclear. We used flow cytometry and immunostaining to reveal the heterogeneity of the immune cells in the cochlea and validated the presence of immune cell gene expression by analyzing existing single-cell RNA-sequencing (scRNAseq) data. We demonstrate that cell types of both the innate and adaptive immune system are present in the cochlea. In response to noise damage, immune cells increase in number. B, T, NK, and myeloid cells (macrophages and neutrophils) are the predominant immune cells present. Interestingly, immune cells appear to respond to noise damage by infiltrating the organ of Corti. Our studies highlight the need to further understand the role of these immune cells within the cochlea after noise exposure.

LY6D as a Chemoresistance Marker Gene and Therapeutic Target for Laryngeal Squamous Cell Carcinoma

Laryngeal squamous cell carcinoma (LSCC) is a common head and neck cancer that is unresponsive to chemotherapy; therefore, understanding the causes of chemotherapy resistance is important. The cancer stem cell (CSC) theory postulates that CSCs are the source of tumor chemoresistance. We enrich laryngeal CSCs to overcome chemoresistance of LSCC. A laryngeal cancer xenograft model was established, and a low dose of cisplatin was administered until chemoresistance arose. A next-generation xenograft model was established using surviving tumor cells, and the test was repeated four times to screen for CSCs. Cell function experiments were performed on each tumor cell generation (m1, m2, m3, and m4). The m3 line, with the highest stemness, was selected for transcriptome sequencing. LY6D was selected for clinical sample validation and functional verification. LY6D expression was detected in 107 laryngeal cancer samples, with high expression in 91 of these samples. LY6D expression was correlated with pathological T and clinical stages, and with cervical lymph node metastasis. The siLY6D group exhibited reduced adhesion and chemoresistance to cisplatin, 5-fluorouracil, and paclitaxel. LY6D is upregulated in laryngeal cancer and may serve as a biomarker for chemoresistance in CSCs. Moreover, LY6D could serve as an alternative antigenic peptide in the targeted treatment of laryngeal cancer.

Emerging Role of Lymphocyte Antigen-6 Family of Genes in Cancer and Immune Cells

Stem Cell Antigen-1 (Sca-1/Ly6A) was the first identified member of the Lymphocyte antigen-6 (Ly6) gene family. Sca-1 serves as a marker of cancer stem cells and tissue resident stem cells in mice. The Sca-1 gene is located on mouse chromosome 15. While a direct homolog of Sca-1 in humans is missing, human chromosome 8—the syntenic region to mouse chromosome 15—harbors several genes containing the characteristic domain known as LU domain. The function of the LU domain in human LY6 gene family is not yet defined. The LY6 gene family proteins are present on human chromosome 6, 8, 11, and 19. The most interesting of these genes are located on chromosome 8q24.3, a frequently amplified locus in human cancer. Human LY6 genes represent novel biomarkers for poor cancer prognosis and are required for cancer progression in addition to playing an important role in immune escape. Although the mechanism associated with these phenotype is not yet clear, it is timely to review the current literature in order to address the critical need for future advancements in this field. This review will summarize recent findings which describe the role of human LY6 genes—LY6D, LY6E, LY6H, LY6K, PSCA, LYPD2, SLURP1, GML, GPIHBP1, and LYNX1; and their orthologs in mice at chromosome 15.

Progression from the Common Lymphoid Progenitor to B/Myeloid PreproB and ProB Precursors during B Lymphopoiesis Requires C/EBPα

The C/EBPα transcription factor is required for myelopoiesis, with prior observations suggesting additional contributions to B lymphopoiesis. Cebpa expression is evident in common lymphoid progenitor (CLP) and preproB cells but is absent in proB and preB cells. We previously observed that marrow lacking the Cebpa +37 kb enhancer is impaired in producing B cells upon competitive transplantation. Additionally, a Cebpa enhancer/promoter-hCD4 transgene is expressed in B/myeloid CFU. Extending these findings, pan-hematopoietic murine Cebpa enhancer deletion using Mx1-Cre leads to expanded CLP, fewer preproB cells, markedly reduced proB and preB cells, and reduced mature B cells, without affecting T cell numbers. In contrast, enhancer deletion at the proB stage using Mb1-Cre does not impair B cell maturation. Further evaluation of CLP reveals that the Cebpa transgene is expressed almost exclusively in Flt3⁺ multipotent CLP versus B cell-restricted Flt3^- CLP. In vitro, hCD4⁺ preproB cells produce both B and myeloid cells, whereas hCD4^- preproB cells only produce B cells. Additionally, a subset of hCD4^- preproB cells express high levels of RAG1-GFP, as seen also in proB cells. Global gene expression analysis indicates that hCD4⁺ preproB cells express proliferative pathways, whereas B cell development and signal transduction pathways predominate in hCD4^- preproB cells. Consistent with these changes, Cebpa enhancer-deleted preproB cells downmodulate cell cycle pathways while upregulating B cell signaling pathways. Collectively, these findings indicate that C/EBPα is required for Flt3⁺ CLP maturation into preproB cells and then for proliferative Cebpa^int B/myeloid preproB cells to progress to Cebpa^lo B cell-restricted preproB cells and finally to Cebpa^neg proB cells.

PU.1 Is Required for the Developmental Progression of Multipotent Progenitors to Common Lymphoid Progenitors

The transcription factor PU.1 is required for the development of mature myeloid and lymphoid cells. Due to this essential role and the importance of PU.1 in regulating several signature markers of lymphoid progenitors, its precise function in early lymphopoiesis has been difficult to define. Here, we demonstrate that PU.1 was required for efficient generation of lymphoid-primed multipotent progenitors (LMPPs) from hematopoietic stem cells and was essential for the subsequent formation of common lymphoid progenitors (CLPs). By contrast, further differentiation into the B-cell lineage was independent of PU.1. Examination of the transcriptional changes in conditional progenitors revealed that PU.1 activates lymphoid genes in LMPPs, while repressing genes normally expressed in neutrophils. These data identify PU.1 as a critical regulator of lymphoid priming and the transition between LMPPs and CLPs.

Visualizing Intrapopulation Hematopoietic Cell Heterogeneity with Self-Organizing Maps of SIMS Data

Characterization of the heterogeneity within stem cell populations, which affects their differentiation potential, is necessary for the design of artificial cultures for stem cell expansion. In this study, we assessed whether self-organizing maps (SOMs) of single-cell time-of-flight secondary ion mass spectrometry (TOF-SIMS) data provide insight into the spectral, and thus the related functional heterogeneity between and within three hematopoietic cell populations. SOMs were created of TOF-SIMS data from individual hematopoietic stem and progenitor cells (HSPCs), lineage-committed common lymphoid progenitors (CLPs), and fully differentiated B cells that had been isolated from murine bone marrow via conventional flow cytometry. The positions of these cells on the SOMs and the spectral variation between adjacent map units, shown on the corresponding unified distance matrix (U-matrix), indicated the CLPs exhibited the highest intrapopulation spectral variation, regardless of the age of the donor mice. SOMs of HSPCs, CLPs, and B cells isolated from young and old mice using the same surface antigen profiles revealed the HSPCs exhibited the most age-related spectral variation, whereas B cells exhibited the least. These results demonstrate that SOMs of single-cell spectra enable characterizing the heterogeneity between and within cell populations that lie along distinct differentiation pathways.