bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fc receptor-like 6 (FCRL6) delineates innate-like B cell progenitors that undergo pre-BCR dependent and independent pathways of natural antibody selection
Authors: Davis Randall S , Honjo Kazuhito , Won Woong-Jai , King Rodney G , Ianov Lara , Crossman David K , Easlick Juliet L , Shakhmatov Mikhail , Khass Mohamed , Vale Andre M , Stephan Robert P , Li Ran 
Published: January 2023

Abstract
Innate-like B-1a B cells produce ‘natural’ antibodies (Abs) to neutralize pathogens and clear neo self-antigens, but the early selection mechanisms that shape their polyreactive repertoires are poorly understood. Fc receptor-like (Fcrl) genes encode surface regulatory proteins preferentially expressed by B cells. Here, we identified a B cell progenitor subset defined by FCRL6 expression, harboring emerging Ighv repertoire, migration, and differentiation properties conducive for natural Ab generation. Receptor-specific monoclonal antibodies identified subpopulations of FCRL6+ pro B cells in E18 fetal liver (FL), neonatal tissues, and adult bone marrow (BM). While it was absent on Hardy Fr. A cells, FCRL6 expression became evident in Fr. B, peaked in Fr. C, and declined in Fr. C′. By the Dorshkind scheme, FCRL6 marked subsets of B-1P and pro B cells in the FL and BM, but was not detected on B-2P cells. Compared to FCRL6− pro B cells, the repressed mitotic, DNA damage repair, and signaling activity of FCRL6+ progenitors, yielded VH repertoires with biased distal Ighv segment accessibility, constrained diversity, and hydrophobic and charged CDR-H3 sequences. Similar features were apparent among B-1a and chronic lymphocytic leukemia (CLL) Ighv sequences. Beyond nascent autoreactivity, VH11 productivity, which predominates phosphatidylcholine-specific B-1a B cell receptors (BCRs), was higher for FCRL6+ cells as was pre-BCR formation, which was required for Myc induction and VH11, but not VH12, B-1a development. Thus, FCRL6 revealed unexpected heterogeneity in the developmental origins, regulation, and selection of natural Abs at the pre-BCR checkpoint with implications for autoimmunity and lymphoproliferative disorders.
The E3 ubiquitin ligase Fbw7 controls survival pathways to prevent apoptosis in mature B cells
Authors: Ramezani-Rad Parham , Leung Charlotte R , Apgar John R , Rickert Robert C 
Published: January 2023

Abstract
Proteolytic processing of proteins is crucial for cellular homeostasis, but also regulates signaling pathways required for effector functions and cell fate decisions. Importantly, dysregulation of proteolysis poses the risk of malignant transformation through abnormal accumulation of oncogenes. The E3 ubiquitin ligase, Fbw7, mandates proteasomal degradation of several oncogenes involved in cellular proliferation, growth, and survival. To elucidate the role of Fbw7 in B cells, we studied the function of Fbw7 in a conditional knockout mouse model. Ablation of Fbw7 during early B cell development diminished the mature recirculating B cell pool in the bone marrow and decreased the B cell population in the spleen. Further, we found a drastic reduction of the B1 cells in the peritoneal cavity. A novel acute deletion model for Fbw7 in mature B1 and B2 cells, showed similar losses of mature B cells in the bone marrow and spleen. Analysis of B cell proteomes revealed defective NF-κB signaling in the absence of Fbw7. BCR-stimulation of Fbw7-deficient B cells ex vivo showed impaired growth, poor proliferation and upregulation of apoptosis. In addition to defective NF-κB signaling, the loss of Fbw7 decreased PI3K pathway signaling, hyperstabilized the well-characterized Fbw7 substrate Myc, and induced pro-apoptotic Bim protein, which supports the role of Fbw7 in survival signaling. Ectopic expression of BCL2 in Fbw7-deficient B cells added context-specific survival signals and largely rescued the apoptotic fate of these cells. Our results indicate for the first time that Fbw7 is a critical regulator in B cells, contributing to survival signaling and controlling cell death in mature B cells.
TFG is upregulated during plasma cell differentiation and regulates apoptosis, ER stress and autophagy in a B cell line
Authors: Steinmetz Tobit Daniel , Reimer Dorothea , Urbanczyk Sophia , Schlötzer-Schrehardt Ursula , Winkler Thomas , Jäck Hans-Martin , Mielenz Dirk 
Published: January 2023

Abstract
Long-term survival and antibody production of plasma cells depend on an intact endoplasmic reticulum (ER) quality control and autophagy. The cytosolic adaptor protein TRK-fused gene (TFG) has been shown to function in ER-Golgi transport, secretion and proteasome regulation. We show here that TFG becomes upregulated by LPS and CpG in primary B1 and B2 cells, and the highest expression of TFG was found in plasma cells.
To address the function of TFG we disrupted the tfg gene in B1-like CH12 lymphoma cells and analyzed mice with heterozygous TFG deletion. TFG KO CH12 cells had higher spontaneous apoptosis rates and were more sensitive to ER stress induced by Tunicamycin, MG132 or an ER-trapped μ heavy chain. Autophagy flux as determined by LC3 turnover, electron microscopy and RFP-GFP-LC3 turnover assays indicated a late suppression of the autophagy pathway in TFG KO CH12 cells. While homozygous deletion of TFG was embryonically lethal, TFG+/− mice had normal B development and germinal center B cells, but significantly less CD138+/TACI+ plasmablast/plasma cells in Peyer’s patches, concomitant with reduced serum IgA.
Based on these data we suggest that TFG is a critical factor of ER homeostasis and autophagy in B cell lines. We propose that TFG counters ER stress by enhancing autophagy and sustain cell survival. Especially plasma cells in Peyer’s patches may critically depend on these TFG-mediated mechanisms.
This work is supported in part by grants TRR130 and GRK1660 from the German Research Foundation to D.M and H.-M.J
Characterization of immune anomalies caused by the ptpn6Ala457Thr mutation associated with a specific form of pulmonary emphysema
Authors: Pineault Marie , Milad Nadia , Lechasseur Ariane , Beaulieu Marie-Josée , Routhier Joanie , Aubin Sophie , Maltais François , Morissette Mathieu 
Published: January 2023

Abstract
A new mutation (PTPN6Ala455Thr) was recently discovered in a family in which many members developed a severe, early and panacinar form of pulmonary emphysema. The mutation was found to be located in the PTPN6 gene, encoding a tyrosine phosphatase known as SHP-1. SHP-1 regulates immunological signaling pathways, such as those involved in B cells maturation and activation.
To characterize the impact of the ptpn6Ala457Thr mutation in a mouse model on subpopulations of B lymphocytes and on their response to immunization.
Proportions of B1a et B2 cells were analyzed in the lungs and spleens of 4-month old mice carrying the ptpn6Ala457Thr mutation by flow cytometry. Serum immunoglobulin levels were assessed. Another group of mice were immunized with a T cells-independent antigen (NP-Ficoll, 50ug i.p.). Plasma was collected at different timepoints after immunization and NP-specific antibodies were measured by ELISA (IgG1, IgG3, IgM and IgA).
Mice carrying the ptpn6Ala457Thr mutation mice had a higher proportion of B1a cells and a lower proportion of B2 cells in the spleen and in the lungs. Total IgG and IgM levels in the serum were higher in ptpn6Ala457Thr mice compared to wild-type animals. Following immunization with NP-Ficoll, ptpn6Ala457Thr mice displayed levels of NP-specific IgG3 and IgM similar to those observed in wild-type mice. However, ptpn6Ala457Thr mice had lower levels of NP-specific IgG1 antibodies compared to the wild-type group.
SHP-1 seems to be important for B cell differentiation and functions, as the mutation led to significant changes in B cell subpopulations. It seems that SHP-1 plays an important role in the immune response to immunization. The full scope of the immunological effects of this mutation requires further study.
Dietary fats directly impact viral immunity by modifying membrane flexibility and how T cells see antigen
Authors: Kolawole Elizabeth Motunrayo , Evavold Brian 
Published: January 2023

Abstract
Dietary supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFAs) have are increasingly consumed for their health benefits and exhibit immunosuppressive effects on both innate and adaptive immunity. Although omega-3s can lead to the production of less inflammatory metabolites, we focused on the direct effects of a high omega 3 diet on T cell activation during viral infection. Specifically, we analyzed T cell recognition of antigen and the resulting functional responses during lymphocytic choriomeningitis (LCMV) infection. The omega-3 based diet manipulated structural lipid content in plasma membranes leading to stiffer T cells which subsequently resulted in reduced frequency and activation of the prevalence immunodominant epitopes. We further found that a high omega-3 diet decreased 2D affinity and number of tetramer positive polyclonal as well as CD8 T cell receptor transgenic cells at peak anti-viral immunity. In addition to affinity, the bond lifetime of antigen recognition was also decreased. This resulted in decreased numbers of SLEC and effector cytokines without impeding viral clearance. Our work indicates that a major effect of dietary omega-3 fatty acids on T cells is the modification of the cell membrane to dampen the initial recognition of antigen leading to decreased but effective immunity.
Characterization of the regulatory TCR repertoire in the context of infection, inflammatory disease, and tumor microenvironment
Authors: Wilson Taylor Leigh , Crawford Jeremy Chase , Samarasinghe Amali , McGargill Maureen Ann , Thomas Paul Glyndwr 
Published: January 2023

Abstract
Regulatory T cells (Tregs) are key negative regulators of the immune system. Conventional T cells use their T cell receptor (TCR) to direct their effector function against specific targets. While much is known about the role of Tregs in their microenvironment, whether Tregs require this TCR specificity to elicit their effector functions is not clear. If so, Treg-specific antigens are also undefined. Investigation of the TCR repertoire can help to answer these questions as it provides insight into the degree of antigen recognition T cells experienced during a response. Since Tregs have been implicated in infection, autoimmunity, allergy, and cancer, we have chosen to characterize the Treg TCR repertoire in murine models for influenza, type I diabetes, asthma, neuroblastoma, and non-small cell lung carcinoma. Using an algorithm generated in our lab, TCRdist, we analyzed features of the TCR repertoire such as clonal expansion, TCR diversity, and V and J region biases. Our preliminary data show lung Tregs from asthmatic mice display the greatest antigen specificity while Tregs in influenza and neuroblastoma have minimal specificity based on clonal expansion and enrichment of TCR motifs. Additionally, we have identified Treg receptors that occur in more than one disease type. These data suggest that Treg TCR-dependency is condition-specific and may be determined by the local tissue as a pathological antigen. Future studies include associating these differences in the repertoire with TCR signaling and Treg functional capacities. Understanding the antigen-specificity of Tregs and identifying highly effective Tregs across diverse diseases can provide opportunities to develop broadly applicable, targeted therapeutics.
Translational regulation directs fate decisions involved in memory CD8 T cell differentiation
Authors: Araki Koichi , Ando Satomi 
Published: January 2023

Abstract
mTOR regulates the formation of memory CD8 T cells that circulate in the blood and are present in lymphoid organs. These memory CD8 T cells are the basis for long-lived T cell immunity and efficiently control re-infection to the previously encountered pathogens. Here, we show that the fate decisions between memory precursor and terminal effector CD8 T cells are regulated by the cap-dependent translation that is the downstream pathway of mTOR. Experiments using RNA interference to inhibit expression of eIF4E, which is a cap-binding protein and a translation initiation factor, in antigen-specific CD8 T cells revealed that high eIF4E expression induced terminal effector cells and low expression promoted memory precursor cells. This eIF4E dependent regulation of memory CD8 T cell differentiation was also confirmed by the overexpression of a constitutively active form of 4E-BP that inhibits cap-dependent translation by binding to eIF4E. RNA immunoprecipitation analysis with anti-eIF4E antibody between naïve and activated CD8 T cells showed that, rather than all mRNAs, the interaction of specific groups of mRNAs (i.e., translation and oxidative phosphorylation) with eIF4E was dynamically regulated during activation of the T cells. Transcripts related to translation and oxidative phosphorylation inefficiently bound to eIF4E in naïve CD8 T cells but the level of competence of these transcripts in binding to eIF4E was significantly improved in activated CD8 T cells. Thus, our data show that eIF4E-dependent translation is actively and selectively regulated during naïve to effector CD8 T cell differentiation and has an important role in fate decisions involved in the formation of memory CD8 T cells.
Single-cell metabolic analysis by mass cytometry reveals distinct transitional states of CD8 T cell differentiation
Authors: Levine Lauren , Hiam Kamir J. , Marquez Diana M. , Tenvooren Iliana , Contreras Diana C , Rathmell Jeffrey Charles , Spitzer Matthew H 
Published: January 2023

Abstract
Mass cytometry permits high-dimensional analysis of diverse aspects of cellular behavior. Here, we adapted this platform to simultaneously profile metabolism, signaling, cell cycle, and effector function with single-cell resolution. Using this approach, we measured enzymes characterizing glycolysis, the TCA cycle, fatty acid oxidation, oxidative phosphorylation, and nutrient transport in conjunction with downstream targets of TCR signaling regulating translation, cell cycle progression, proliferation and cytotoxicity. By integrating these functional measurements with surface markers and transcription factors delineating CD8 T cell differentiation and fate acquisition, unsupervised high-dimensional single-cell metabolic analysis by mass cytometry permits identification of unique metabolic and differentiation states of extremely rare cell populations, such as antigen-specific T cells. We interrogated antigen-specific CD8 T cell activation in vitro in addition to the trajectory of the CD8 T cell response over the first nine days of Listeria monocytogenes infection, a well-characterized model for studies of T cell differentiation. This integrated, high-dimensional approach revealed a novel, activated, and highly metabolically active transitional T cell subset emerging at four days post-infection. These cells simultaneously exhibit glycolytic and oxidative functional programs that we propose represents a key metabolic inflection point in CD8+ T cell differentiation. This approach should be useful for mechanistic investigations of metabolic regulation of immune responses in vivo.
T cell-intrinsic expression of HIC1 links retinoic acid to tissue residency
Authors: Bramhall Michael , Rodrigues Grace , Christo Susan , Mackay Laura , Zaph Colby 
Published: January 2023

Abstract
The interaction between micronutrients and the immune system is emerging as a key control point in immune cell function in homeostasis and disease. For example, the vitamin A metabolite all-trans retinoic acid (atRA) has established roles in immune cell migration and effector function. Vitamin A deficiency results in a significant reduction in intestinal immune cells, which is thought to be associated with a lack of intestinal homing receptor expression and reduced migration to the intestine. However, the precise molecular pathways controlling intestinal immune cell homeostasis remains unclear.
Here, we show that the atRA-inducible BTB-POZ transcriptional repressor Hypermethylated in cancer 1 (HIC1, ZBTB29) controls intestinal T cell residency. Mice with a T cell-intrinsic deletion of HIC1 (Hic1ΔT mice) have reduced numbers of CD69+ CD103+ tissue resident memory T (TRM) cells in the intestine, demonstrating that the atRA/HIC1 axis is critical for establishing and maintaining TRM cells. Further, following influenza A virus infection, numbers of TRM cells in the lungs are significantly reduced in Hic1ΔT mice, as well as in mice treated with the pan-retinoic acid receptor inhibitor BMS493, or in mice with a T cell-specific deletion of RARa (RaraΔT mice).
Consistent with this, activation of naive CD8+ T cells from mice or humans in the presence of IL-2, IL-15, TGFβ and atRA results in the generation of CD69+ CD103+ ‘TRM-like’ cells that share the transcriptional profile of bona fide TRM cells. Taken together, these results identify atRA as a critical regulator of T cell tissue residency, acting by inducing expression of HIC1 and promoting the tissue residency gene program.
Essential respiratory chain subunits encoded by mitochondrial DNA control plasma cell development
Authors: Urbanczyk Sophia , Baris Olivier , Mougiakakos Dimitrios , Wiesner Rudolf , Jäck Hans-Martin , Mielenz Dirk 
Published: January 2023

Abstract
The contribution of mitochondrial metabolism to plasma cell development is largely unknown. To define the function of the mitochondrial respiratory chain during B cell activation and differentiation, we used a mouse model in which CD23-Cre drives the expression of a dominant-negative mutant of the mitochondrial helicase Twinkle (DNTwinkle) and the reporter GFP in mature B cells. DNTwinkle expression induces mitochondrial DNA (mtDNA) deletions in dividing cells and results in impaired respiratory chain activity. Flow cytometry in non-immunized DNTwinkle mice did not reveal a difference in either total cell numbers or frequencies of mature B cell subsets. However, only about 8% of the plasma cells in the bone marrow were positive for DNTwinkle/GFP, indicating that these cells have a significant disadvantage in the presence of wildtype plasma cells. T-dependent immunization showed a decreased primary immune response, whereas the secondary immune response was not affected. Strikingly, in immunized mice, all antigen-specific plasma cells in the bone marrow were GFP-negative, again highlighting the advantage of escaper cells. Comparing to in vitro stimulated wild-type B cells, DNTwinkle-positive splenic B cells showed comparable survival, but proliferation, Ig class switch, and plasmablast differentiation were impaired. Also, OxPhos was reduced, but glycolysis and lactate secretion were increased. Finally, AMPK activation was enhanced along with reduced mTOR activity, which could explain the observed impaired Blimp-1 expression and plasmablast differentiation of DNTwinkle B cells. Our results place mitochondrial DNA replication and respiratory chain activity upstream of mTOR and Blimp-1 via AMPK.
Role of SAM in Plasma Cell Differentiation and Function
Authors: Sievert Evelyn P , Franke Marissa , Sciammas Roger 
Published: January 2023

Abstract
Plasma cells (PCs) are terminally differentiated B cells which secrete high levels of immunoglobulin (Ig). While Ig is essential for neutralizing and clearing pathogens, an excess of Ig is detrimental in autoimmune conditions. The transcription factor Blimp-1 is necessary and sufficient for this transition to PCs and is known to regulate Ig secretion. PC differentiation is reliant on multiple levels of regulation - epigenetic, post-transcriptional, and translational, which we hypothesize are dependent on methyltransferase activity for dynamic methylation.
PCs also upregulate high levels of CD98, which functions as a membrane transporter for amino acids such as methionine, and thus initialization of the methionine cycle. In this cycle, methionine adenosyltransferase (MAT) coordinates the production of the methyl donor S-adenosylmethionine (SAM) from methionine. We are interested in determining whether this strong expression of CD98 is dependent on Blimp-1 or regulated by PCs, and to understand the role of SAM is this differentiation event.
Utilizing a Blimp-1-YFP reporter mouse line, we are able to detect the transition to PCs in-vitro and study the requirement for SAM during this transition. Depletion of the precursor to SAM, methionine, resulted in a loss of PC number and secretory capacity. To specifically target the role of SAM for PCs, we treated in-vitro cultured PCs with inhibitors of MAT2A. Preliminary data provides evidence that inhibition of SAM reduces PC phenotype, function, and viability. We aim to determine the role of SAM in Ig secretion through transcriptional analysis and metabolomics, and hypothesize that Ig post-transcriptional regulation in PCs is controlled by methyltransferase activity.
H3K27me3 demethylases are important epigenetic regulators of B cell differentiation
Authors: Kania Anna , Price Madeline , Scharer Christopher D. , Boss Jeremy M 
Published: January 2023

Abstract
The humoral immune response relies on robust differentiation of naïve B cells into antibody secreting plasma cells (PC) in response to foreign, but not self-antigens. To ensure proper immune responses, B cell differentiation is regulated through processes that remodel the epigenome. The histone modification H3 lysine 27 trimethylation (H3K27me3) is associated with a repressive chromatin state and gene silencing. This histone modification is deposited by EZH2, which has been shown to regulate all stages of B cell differentiation leading to PC. However, a role for the two demethylases UTX and JMJD3 that remove H3K27me3 in B cells is still to be elucidated. To determine how these enzymes modulate B cell differentiation, we crossed Utxfl/flJmjd3fl/flmice onto the Cd19Cre/+background (dKO mice). Stimulation of Cd19Cre/+(CreCtrl) and dKO mice with the T cell independent antigen LPS led to a significant increase in PC in dKO mice. This phenotype was attributed to enhanced differentiation of marginal zone (MZ), but not follicular B cells (FoB). UTX- and JMJD3-deficient PC unregulated genes associated with oxidative phosphorylation metabolism and resulted in a significantly higher spare respiratory capacity. In response to infection with influenza virus, we observed a significant increase in GC B cells in UTX- and JMJD3-deficient mice. Taken together, our data place H3K27me3 demethylases as critical epigenetic regulators that restrict B cell responses to T cell dependent and independent stimuli.