Recruitment of plasma cells from IL-21-dependent and IL-21-independent immune reactions to the bone marrow.

Bone marrow plasma cells (BMPC) are the correlate of humoral immunity, consistently releasing antibodies into the bloodstream. It remains unclear if BMPC reflect different activation environments or maturation of their precursors. Here we define human BMPC heterogeneity and track the recruitment of antibody-secreting cells (ASC) from SARS-CoV-2 vaccine immune reactions to the bone marrow (BM). Trajectories based on single-cell transcriptomes and repertoires of peripheral and BM ASC reveal sequential colonisation of BMPC compartments. In activated B cells, IL-21 suppresses CD19 expression, indicating that CD19low-BMPC are derived from follicular, while CD19high-BMPC originate from extrafollicular immune reactions. In primary immune reactions, both CD19low- and CD19high-BMPC compartments are populated. In secondary immune reactions, most BMPC are recruited to CD19high-BMPC compartments, reflecting their origin from extrafollicular reactivations of memory B cells. A pattern also observable in vaccinated-convalescent individuals and upon diphtheria/tetanus/pertussis recall-vaccination. Thus, BMPC diversity reflects the evolution of a given humoral immune response.

IL-4-secreting CD40L+ MAIT cells support antibody production in the peripheral blood of Heonch-Schönlein purpura patients.

OBJECTIVE: Here, we explored the phenotype and function of MAIT cells in the peripheral blood of patients with HSP. METHODS: Blood samples from HSP patients and HDs were assessed by flow cytometry and single-cell RNA sequencing to analyze the proportion, phenotype, and function of MAIT cells. Th-cytokines in the serum of HSP patients were analyzed by CBA. IgA in cocultured supernatant was detected by CBA to analyze antibody production by B cells. RESULTS: The percentage of MAIT cells in HSP patients was significantly reduced compared with that in HDs. Genes related to T cell activation and effector were up-regulated in HSP MAIT cells, indicating a more activated phenotype. In addition, HSP MAIT cells displayed a Th2-like profile with the capacity to produce more IL-4 and IL-5, and IL-4 was correlated with IgA levels in the serum of HSP patients. Furthermore, CD40L was up-regulated in HSP MAIT cells, and CD40L+ MAIT cells showed an increased ability to produce IL-4 and to enhance IgA production by B cells. CONCLUSION: Our data demonstrate that MAIT cells in HSP patients exhibit an activated phenotype. The enhanced IL-4 production and CD40L expression of MAIT cells in HSP patients could take part in the pathogenesis of HSP.

CD39 and CD326 Are Bona Fide Markers of Murine and Human Plasma Cells and Identify a Bone Marrow Specific Plasma Cell Subpopulation in Lupus.

Antibody-secreting cells (ASCs) contribute to immunity through production of antibodies and cytokines. Identification of specific markers of ASC would allow selective targeting of these cells in several disease contexts. Here, we performed an unbiased, large-scale protein screening, and identified twelve new molecules that are specifically expressed by murine ASCs. Expression of these markers, particularly CD39, CD81, CD130, and CD326, is stable and offers an improved resolution for ASC identification. We accessed their expression in germ-free conditions and in T cell deficient mice, showing that at least in part their expression is controlled by microbial- and T cell-derived signals. Further analysis of lupus mice revealed the presence of a subpopulation of LAG-3- plasma cells, co-expressing high amounts of CD39 and CD326 in the bone marrow. This population was IgM+ and correlated with IgM anti-dsDNA autoantibodies in sera. Importantly, we found that CD39, CD81, CD130, and CD326 are also expressed by human peripheral blood and bone marrow ASCs. Our data provide innovative insights into ASC biology and function in mice and human, and identify an intriguing BM specific CD39++CD326++ ASC subpopulation in autoimmunity.

RGL2 as an age-dependent factor regulates colon cancer progression.

Colon cancer is the fourth leading cause of cancer-related death, and exhibited clinical differences among patients of different ages, including malignancy, metastasis, and mortality rate. Few studies, however, focus on the communications between aging and colon cancer. Here we identified age-dependent differentially expressed genes (DEGs) in colon cancer using TCGA transcriptome data. Through analyzing multi-omics high throughput data, including ATAC-Seq, DNaseI-Seq and ChIP-Seq, we obtained six age-dependent transcription factors in colon cancer, and their age-dependent targets, significantly affecting patients' overall survivals. Transcription factor ETS1 potentially functioned in both aging process and colon cancer progression through regulating its targets, RGL2 and SLC2A3. In addition, comparing with its relative lower expression levels in elderly patients, higher levels of RGL2 were detected in young patients, and significantly associated with larger tumor size, higher metastasis, and invasions of colon cancer, consistent with the clinical traits that young patients' colon cancer exhibited late stages with more aggressiveness. Thus, these elements may serve as keys linking aging and colon cancer, and providing new insights and basis for mechanism researches, as well as diagnosis and therapies of colon cancer, especially in young patients.

LYAR Promotes Colorectal Cancer Progression by Upregulating FSCN1 Expression and Fatty Acid Metabolism.

Colorectal cancer (CRC) is a highly malignant tumor associated with poor prognosis, yet the molecular mechanisms are not fully understood. In this study, we showed that LYAR, a nucleolar protein, is expressed at a higher level in CRC tissue than in adjacent normal tissue and that LYAR expression is closely associated with distant CRC metastasis. LYAR not only significantly promotes the migration and invasion of CRC cells in vitro, but knockdown (KD) of LYAR in CRC cells also inhibits xenograft tumor metastasis in vivo. Microarray analysis of LYAR KD cells combined with a chromatin immunoprecipitation (ChIP) assay, gene reporter assay, and rescue experiment indicated that FSCN1 (encoding fascin actin-bundling protein 1 (Fascin-1)) serves as a novel key regulator of LYAR-promoted migration and invasion of CRC cells. Knockdown of FSCN1 significantly inhibits subcutaneous tumorigenesis of CRC cells and leads to the downregulation of FASN and SCD, genes encoding key enzymes in fatty acid synthesis. In summary, this study reveals a novel mechanism by which LYAR promotes tumor cell migration and invasion by upregulating FSCN1 expression and affecting fatty acid metabolism in CRC.

Senescence-associated genes and non-coding RNAs function in pancreatic cancer progression.

Pancreatic cancer is a major cause of mortality with a poor diagnosis and prognosis that most often occurs in elderly patients. Few studies, however, focus on the interplay of age and pancreatic cancer at the transcriptional level. Here we evaluated the possible roles of age-dependent, differentially expressed genes (DEGs) in pancreatic cancer. These DEGs were used to construct a correlation network and clustered in six gene modules, among which two modules were highly correlated with patients' survival time. Integrating different datasets, including ATAC-Seq and ChIP-Seq, we performed multi-parallel analyses and identified eight age-dependent protein coding genes and two non-coding RNAs as potential candidates. These candidates, together with KLF5, a potent functional transcription factor in pancreatic cancer, are likely to be key elements linking cellular senescence and pancreatic cancer, providing insights on the balance between them, as well as on diagnosis and subsequent prognosis of pancreatic cancer.

Salmonella SiiE prevents an efficient humoral immune memory by interfering with IgG+ plasma cell persistence in the bone marrow.

Serum IgG, which is mainly generated from IgG-secreting plasma cells in the bone marrow (BM), protects our body against various pathogens. We show here that the protein SiiE of Salmonella is both required and sufficient to prevent an efficient humoral immune memory against the pathogen by selectively reducing the number of IgG-secreting plasma cells in the BM. Attenuated SiiE-deficient Salmonella induces high and lasting titers of specific and protective Salmonella-specific IgG and qualifies as an efficient vaccine against Salmonella A SiiE-derived peptide with homology to laminin ß1 is sufficient to ablate IgG-secreting plasma cells from the BM, identifying laminin ß1 as a component of niches for IgG-secreting plasma cells in the BM, and furthermore, qualifies it as a unique therapeutic option to selectively ablate IgG-secreting plasma cells in autoimmune diseases and multiple myeloma.

CXCR4-CXCL12 interaction is important for plasma cell homing and survival in NZB/W mice.

Antibody-secreting cells (ASCs), including short-lived plasmablasts and long-lived memory plasma cells (LLPCs), contribute to autoimmune pathology. ASCs, particularly LLPCs, refractory to conventional immunosuppressive drugs pose a major therapeutic challenge. Since stromal cells expressing C-X-C motif chemokine-12 (CXCL12) organize survival niches for LLPCs in the bone marrow, we investigated the effects of CXCL12 and its ligand CXCR4 (C-X-C chemokine receptor 4) on ASCs in lupus mice (NZB/W). Fewer adoptively transferred splenic ASCs were retrieved from the bone marrow of recipient immunodeficient Rag1-/- mice when the ASCs were pretreated with the CXCR4 blocker AMD3100. CXCR4 blockade also significantly reduced anti-OVA ASCs in the bone marrow after secondary immunization with OVA. In this study, AMD3100 efficiently depleted ASCs, including LLPCs. After two weeks, it decreased the total number of ASCs in the spleen and bone marrow by more than 60%. Combination with the proteasome inhibitor bortezomib significantly enhanced the depletion effect of AMD3100. Continuous long-term (five-month) CXCR4 blockade with AMD3100 after effective short-term LLPCs depletion kept the number of LLPCs in the bone marrow low, delayed proteinuria development and prolonged the survival of the mice. These findings identify the CXCR4-CXCL12 axis as a potential therapeutic target likely due to its importance for ASC homing and survival.

Shining the Light on Senescence Associated LncRNAs.

Cellular senescence can be described as a complex stress response that leads to irreversible cell cycle arrest. This process was originally described as an event that primary cells go through after many passages of cells during cell culture. More recently, cellular senescence is viewed as a programmed process by which the cell displays a senescence phenotype when exposed to a variety of stresses. Cellular senescence has been implicated in tumor suppression and aging such that senescence may contribute to both tumor progression and normal tissue repair. Here, we review different forms of cellular senescence, as well as current biomarkers used to identify senescent cells in vitro and in vivo. Additionally, we highlight the role of senescence-associated long noncoding RNAs (lncRNAs).

Hepatocellular Carcinoma-propagating Cells are Detectable by Side Population Analysis and Possess an Expression Profile Reflective of a Primitive Origin.

The recent identification of "Side Population" (SP) cells in a number of unrelated human cancers has renewed interests in the hypothesis of cancer stem cells. Here we isolated SP cells from HepG2 cells and 18 of the 21 fresh hepatocellular carcinoma (HCC) tissue samples. These SP cells have higher abilities of forming spheroids, invasion and migration. Tumors could generate only from SP, not non-SP (NSP), cells in a low dose of subcutaneous injection to the NOD/SCID mice (5 × 102 cells/mouse). The mRNA microarray analysis of the SP vs. NSP cells isolated from HepG2 cells revealed that the SP cells express higher levels of pluripotency- and stem cell-associated transcription factors including Klf4, NF-Ya, SALL4 and HMGA2. Some of the known hepatobiliary progenitor/stem cell markers, such as Sox9 was also up-regulated. RT-qPCR analysis of the gene expression between SP cells and NSP cells isolated from both HepG2 cells and HCC tissue samples showed that most of the tested mRNAs' changes were in consistent with the microarray data, including the general progenitor/stem cells markers such as Klf4, NF-Ya, SALL4 and HMGA2, which were up-regulated in SP cells. Our data indicates that HCC cancer stem cells exist in HepG2 and HCC fresh tissue samples and can be isolated by SP assay.

Bortezomib Plus Continuous B Cell Depletion Results in Sustained Plasma Cell Depletion and Amelioration of Lupus Nephritis in NZB/W F1 Mice.

METHODS: NZB/W F1 mice were treated with: 1) anti-CD20, 2) anti-CD20 plus bortezomib, 3) anti-CD20 plus anti-LFA-1/anti-VLA-4 blocking antibodies, 4) anti-CD20 plus bortezomib and anti-LFA-1/anti-VLA4 blocking antibodies. Short- and long-lived plasma cells including autoreactive cells in the bone marrow and spleen were enumerated by flow cytometry and ELISPOT seven days after treatment. Based on these data in another experiment, mice received one cycle of anti-CD20 plus bortezomib followed by four cycles of anti-CD20 therapy every 10 days and were monitored for its effect on plasma cells and disease. RESULTS: Short-lived plasma cells in bone marrow and spleen were efficiently depleted by all regimens targeting plasma cells. Conversely, LLPCs and anti-dsDNA-secreting plasma cells in bone marrow and spleen showed resistance to depletion and were strongly reduced by bortezomib plus anti-CD20. The effective depletion of plasma cells by bortezomib complemented by the continuous depletion of their precursor B cells using anti-CD20 promoted the persistent reduction of IgG anti-dsDNA antibodies, delayed nephritis and prolonged survival in NZB/W F1 mice. CONCLUSIONS: These findings suggest that the effective depletion of LLPCs using bortezomib in combination with a therapy that continuously targeting B cells as their precursors may prevent the regeneration of autoreactive LLPCs and, thus, might represent a promising treatment strategy for SLE and other (auto)antibody-mediated diseases.

γ-Secretase directly sheds the survival receptor BCMA from plasma cells.

Survival of plasma cells is regulated by B-cell maturation antigen (BCMA), a membrane-bound receptor activated by its agonist ligands BAFF and APRIL. Here we report that γ-secretase directly cleaves BCMA, without prior truncation by another protease. This direct shedding is facilitated by the short length of BCMA's extracellular domain. In vitro, γ-secretase reduces BCMA-mediated NF-κB activation. In addition, γ-secretase releases soluble BCMA (sBCMA) that acts as a decoy neutralizing APRIL. In vivo, inhibition of γ-secretase enhances BCMA surface expression in plasma cells and increases their number in the bone marrow. Furthermore, in multiple sclerosis, sBCMA levels in spinal fluid are elevated and associated with intracerebral IgG production; in systemic lupus erythematosus, sBCMA levels in serum are elevated and correlate with disease activity. Together, shedding of BCMA by γ-secretase controls plasma cells in the bone marrow and yields a potential biomarker for B-cell involvement in human autoimmune diseases.

The proteasome inhibitior bortezomib depletes plasma cells and ameliorates clinical manifestations of refractory systemic lupus erythematosus.

OBJECTIVES: To investigate whether bortezomib, a proteasome inhibitor approved for treatment of multiple myeloma, induces clinically relevant plasma cell (PC) depletion in patients with active, refractory systemic lupus erythematosus (SLE). METHODS: Twelve patients received a median of two (range 1-4) 21-day cycles of intravenous bortezomib (1.3 mg/m(2)) with the coadministration of dexamethasone (20 mg) for active SLE. Disease activity was assessed using the SLEDAI-2K score. Serum concentrations of anti-double-stranded DNA (anti-dsDNA) and vaccine-induced protective antibodies were monitored. Flow cytometry was performed to analyse peripheral blood B-cells, PCs and Siglec-1 expression on monocytes as surrogate marker for type-I interferon (IFN) activity. RESULTS: Upon proteasome inhibition, disease activity significantly declined and remained stable for 6 months on maintenance therapies. Nineteen treatment-emergent adverse events occurred and, although mostly mild to moderate, resulted in treatment discontinuation in seven patients. Serum antibody levels significantly declined, with greater reductions in anti-dsDNA (∼60%) than vaccine-induced protective antibody titres (∼30%). Bortezomib significantly reduced the numbers of peripheral blood and bone marrow PCs (∼50%), but their numbers increased between cycles. Siglec-1 expression on monocytes significantly declined. CONCLUSIONS: These findings identify proteasome inhibitors as a putative therapeutic option for patients with refractory SLE by targeting PCs and type-I IFN activity, but our results must be confirmed in controlled trials.

Autoantibodies from long-lived 'memory' plasma cells of NZB/W mice drive immune complex nephritis.

OBJECTIVES: We have previously shown that both short- and long-lived plasma cells (PCs) significantly contribute to autoantibody production in NZB/W mice as a model of lupus nephritis. The aim of this study was to determine the role of autoreactive long-lived (memory) PCs refractory to immunosuppression and B cell depletion in the pathogenesis of systemic lupus erythematosus. METHODS: Splenic CD138+ antibody-secreting cells (ASCs) from >6-month-old NZB/W mice with high titres of anti-dsDNA autoantibodies or from Balb/c mice 5 days after secondary immunisation with ovalbumin (OVA) were adoptively transferred to immunodeficient Rag1(-/-) mice, in which the development of nephritis was investigated by measuring proteinuria. Total IgG and IgM as well as anti-dsDNA and anti-OVA antibody levels were followed up by ELISA. After 21 weeks the recipient mice were sacrificed so that PCs in spleen and bone marrow could be analysed using ELISPOT and flow cytometry and renal immunohistology performed. RESULTS: The adoptive transfer of NZB/W and anti-OVA ASCs resulted in the continuous generation of anti-dsDNA antibodies and anti-OVA antibodies, respectively, exclusively by long-lived PCs that had homed to the spleen and bone marrow of recipient Rag1(-/-) mice. Rag1(-/-) mice generating autoantibodies including anti-dsDNA had reduced survival, proteinuria and immune complex nephritis with C1q, C3, IgG and IgM deposits 21 weeks after transfer. CONCLUSIONS: These findings demonstrate that autoantibodies exclusively secreted by long-lived (memory) PCs contribute to autoimmune pathology and should be considered as candidate targets for future therapeutic strategies.

Bone marrow of NZB/W mice is the major site for plasma cells resistant to dexamethasone and cyclophosphamide: implications for the treatment of autoimmunity.

Antibodies contribute to the pathogenesis of many chronic inflammatory diseases, including autoimmune disorders and allergies. They are secreted by proliferating plasmablasts, short-lived plasma cells and non-proliferating, long-lived memory plasma cells. Memory plasma cells refractory to immunosuppression are critical for the maintenance of both protective and pathogenic antibody titers. Here, we studied the response of plasma cells in spleen, bone marrow and inflamed kidneys of lupus-prone NZB/W mice to high-dose dexamethasone and/or cyclophosphamide. BrdU+, dividing plasmablasts and short-lived plasma cells in the spleen were depleted while BrdU- memory plasma cells survived. In contrast, all bone marrow plasma cells including anti-DNA secreting cells were refractory to both drugs. Unlike bone marrow and spleen, which showed a predominance of IgM-secreting plasma cells, inflamed kidneys mainly accommodated IgG-secreting plasma cells, including anti-DNA secreting cells, some of which survived the treatments. These results indicate that the bone marrow is the major site of memory plasma cells resistant to treatment with glucocorticoids and anti-proliferative drugs, and that inflamed tissues and secondary lymphoid organs can contribute to the autoreactive plasma cell memory. Therefore, new strategies targeting autoreactive plasma cell memory should be considered. This could be the key to finding a curative approach to the treatment of chronic inflammatory autoantibody-mediated diseases.