bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation-dependent Posttranscriptional Regulation of CD40L is Required for an Optimal Germinal Center (GC) response
Authors: Narayanan Bitha , De Maio Diego Prado , Voskoboynik Katie , La Porta James , Xie Ping , Covey Lori R 
Published: January 2023

Abstract
We have previously shown that regulation of CD40L occurs in part through a posttranscriptional mechanism of activation-induced mRNA stability. This pathway is engaged at extended times of activation and is mediated by the binding of a polypyrimidine tract binding protein (PTBP1) complex to the 3′UTR of the CD40L mRNA. This process leads to sustained expression of CD40L on CD4 T cells at a time when overall transcript levels are low. To assess the role of this regulatory pathway on an ongoing immune response we engineered a novel knock-in mouse (CD40LΔ5) that lacked the PTBP1 stability element and challenged mice with NP-KLH and SRBCs. Examination of splenic subsets prior to immunization revealed no difference in number or ratio between mutant and WT mice. However, after immunization there were significant decreases in T-dependent antibodies (Abs) and these differences were exacerbated with secondary challenge. In contrast, there were no differences in Ab response to a T-independent antigen. In total, CD40LΔ5 mice displayed significant changes in multiple aspects of the GC response including reduced levels of plasma cells, memory cells and GL7+ B cells. However, there were no observed differences in the number of Tfh cells between mutant and WT mice. Evaluation of GC structure in splenic sections revealed highly disordered GCs in CD40LΔ5 compared to WT mice at 8 days following immunization with SRBCs. Therefore, we hypothesize that the T cell activation-induced stabilization of the CD40L message and the subsequent surface expression of the protein is critical for development of a robust GC response and this occurs on one level by directly impacting the structural architecture of the GC.
Characterization and transcriptional profiling of tissue-resident memory CD4+ T cells
Authors: Nguyen Quynh P , Deng Tianda , Goldrath Ananda W 
Published: January 2023

Abstract
In response to acute infection, naive T cells proliferate and differentiate into effector cells, which aid in clearing pathogens, and long-lived memory cells, which provide protection from reinfection. CD4+ T cells play a key role in this response because they mediate the activity of innate cell, B cell, and CD8+ T cell immunity. Memory T cells have classically been categorized into central memory cells (TCM), which circulate between blood and secondary lymphoid organs, or effector memory cells (TEM), which can enter non-lymphoid tissues. Recently, evidence for a third subset of memory cells has emerged, called tissue-resident memory T cells (TRM), which populate barrier surfaces such as skin and intestinal mucosa. TRM serve as sentinels at the sites of pathogen exposure, coordinating the initial response and providing a significant boost to immunity. The ontogeny and regulation of CD8+ TRM differentiation have been characterized in recent years, but less is known about CD4+TRM within the context of antiviral immunity. Using bulk and single-cell RNA-seq and ATAC-seq, we characterize the transcriptional and epigenetic profiles of viral-specific CD4+ T cells in the small intestine. We demonstrate that antigen-specific CD4+ TRM have a transcriptional profile distinct from circulating populations. CD4+ TRM can also be distinguished from circulating memory CD4+ T cells by expression of CD69, Ly6C, and CD27 cell-surface receptors. Additionally, we examine the role of transcriptional regulators, including Bcl6, Prdm1, and Id2/Id3, in CD4+ TRM development. A better understanding of CD4+ TRM will allow us to harness the protective capacity of this memory population and modulate activity in infection or inflammatory diseases.
The role of Aquaporin-4 in T cell activation
Authors: Nicosia Michael , Beavers Ashley M , Farr George W , McGuirk Paul R , Pelletier Marc , Valujskikh Anna 
Published: January 2023

Abstract
Aquaporins (AQPs) are membrane channels that mediate a variety of biological processes via water and other small molecule movement. Several aquaglyceroporins have been shown to regulate key immune functions. However, the role of AQP4 in immune cells is poorly characterized. We recently reported that AQP4 is expressed by both naïve and memory CD4 and CD8 T cells. Furthermore, AQP4 blockade with a small molecule inhibitor, AER-270, reduced T cell activation and proliferation leading to a significant prolongation of fully MHC-mismatched murine heart allograft survival. The goal of this study was to determine the mechanisms by which AQP4 facilitates T cell activation and TCR signaling. Wild-type (WT) but not AQP4−/− T cells treated with AER-270 were protected from lysis in a hypoosmotic shock assay demonstrating AQP4 requirement for water transport in T cells. Following αCD3/αCD28 stimulation, AQP4−/− T cells demonstrated inferior activation compared to WT T cells. Similar decreased activation was observed after treatment of WT T cells with AER-270. Consistent with reduced T cell activation, AQP4 inhibition diminished Ca2+flux in WT but not AQP4−/− T cells in response to TCR crosslinking. AQP4 inhibition also resulted in altered pattern of protein tyrosine phosphorylation at 2 min following TCR crosslinking. These results indicate that despite T cell expression of several water channels, AQP4 function is critical for optimal T cell activation and functions. Our study identifies a novel role of water channels in T cell biology and suggests AQP4 inhibition as a promising strategy to modulate T cell alloresponses following transplantation.
MAP kinase phosphatase (Mkp)-1 Controls Program Death-Ligand (PD-L)1 Expression during Sepsis
Authors: Kirk Sean G , Batty Abel J , Wang Xiantao , Li Jinhui , White William M. , Ackerman William E. , Nelin Leif D. , Buhimschi Irina , Hafner Markus , Liu Yusen 
Published: January 2023

Abstract
Mkp-1 is a critical negative regulator of the inflammatory response, and plays a crucial role for bacterial clearance in an animal model of sepsis. Mkp-1−/− mice exhibit augmented inflammation, increased bacterial burden, elevated organ damage, and increase mortality relative to Mkp-1+/+ mice following E. coli infection. To understand the functions of Mkp-1, we performed RNA-seq with mouse livers. Under normal conditions, 357 genes were differentially expressed between Mkp-1+/+ and Mkp-1−/− mice. However, following E. coli infection &gt; 5,400 genes displayed differential expression between the two groups. Among genes upregulated by E. coli infection and exacerbated by Mkp-1−/− are PD-L1 and CTLA-4, two key immune checkpoint proteins. Interestingly, the expression of PD-L1 and CTLA-4 were highly correlated with the expression of IL-6, IL-10, and STAT3. qRT-PCR and Western blot analyses verified E. coli infection-induced PD-L1 expression and further exacerbation in Mkp-1−/− mice. Examination of the RNA-seq dataset revealed a clear interferon signature. ELISA analyses on the serum revealed low IFN-β levels in uninfected Mkp-1+/+ and Mkp-1−/− mice, increased IFN-β levels in E. coli-infected Mkp-1+/+ mice, and further augmented IFN-β levels in E. coli-infected Mkp-1−/− mice. Similarly, Mkp-1−/− bone marrow-derived macrophages also produced more IFN-β following stimulation with either LPS or heat-killed E. coli than Mkp-1+/+ macrophages. Our studies indicate that expression of immune check point proteins, PD-L1 and CTLA-4, are controlled by Mkp-1 during microbial infection. Our studies also suggest that exaggerated expression of type I interferons and PD-L1 contribute to the phenotypes of Mkp-1−/− mice in the model of sepsis.
Suppression of Aiolos and Ikaros expression by lenalidomide reduces human ILC3–ILC1/NK cell transdifferentiation
Authors: Mazzurana Luca , Forkel Marianne , Rao Anna , Van Acker Aline , Kokkinou Efthymia , Ichiya Tamaki , Almer Sven , Höög Charlotte , Friberg Danielle , Mjösberg Jenny 
Published: January 2023

Abstract
The Ikaros family of transcription factors (TFs) are important regulators of lymphocyte function. However, their roles in human innate lymphoid cell (ILC) function remain unclear. Here, we found that Ikaros (IKZF1) is expressed by all ILC subsets, including NK cells, in blood, tonsil and gut, while Helios (IKZF2) is preferentially expressed by ILC3 in tonsil and gut. Aiolos (IKZF3) followed the expression pattern of T-bet and Eomes, being predominantly expressed by ILC1 and NK cells. Differentiation of IFN-γ-producing ILC1 and NK cells from ILC3 by IL-1β plus IL-12-stimulation was associated with upregulation of T-bet and Aiolos. Selective degradation of Aiolos and Ikaros by lenalidomide suppressed ILC1 and NK cell differentiation and expression of ILC1 and NK cell-related transcripts (LEF1, PRF1, GRZB, CD244, NCR3, IRF8). In line with reduced ILC1/NK cell differentiation we observed an increase in the expression of the ILC3-related TF Helios, as well as ILC3 transcripts (TNFSF13B, IL22, NRP1 and RORC) and in the frequency of IL-22 producing ILC3 in cultures with IL-1β and IL-23. These data suggest that suppression of Aiolos and Ikaros expression inhibits ILC1 and NK cell differentiation while ILC3 function is maintained. Hence, our results open up for new possibilities in targeting Ikaros family TFs for modulation of type 1/3 immunity in inflammation and cancer.
Development of functional mannose binding lectin is delayed in extremely low birth weight infants
Authors: Dean Melinda M , Lopez Genghis H , Liley Helen G , Heatley Susan L , Minchinton Robyn M 
Published: January 2023

Abstract

Background
Mannose binding lectin (MBL) is a liver derived plasma pattern recognition molecule that plays an important role in innate immune defence. Genetically driven deficiencies in MBL level and function are associated with increased frequency and severity of infection, and increased prevalence of autoimmune and chronic inflammatory diseases. Extremely low birth weight infants (ELBWI) are at increased risk of acquiring infection and innate immunity is particularly important in this group. We assessed functional MBL level and capacity to activate the complement cascade in ELBWI.

Methods
ELBW infants (&lt; 1500 g, n=141) were recruited from the Mater Mothers’ Hospital (informed parental consent, ethics #492M). Whole blood was collected into EDTA coated tubes at birth (cord blood), and at D7 and D28 postpartum (heel prick). Functional MBL level and C4 deposition capacity were determined by ELISAs. MBL genotype was determined by PCR. MBL oligomerisation was determined by western blot. Full birth weight infants (n=190) and healthy adult blood donors (n=236) were used as comparators (unpaired t-test P&lt;0.05).

Results
Compared to both full term neonates and adults, new born ELBW infants had significantly reduced MBL level (both P&lt;0.001) and C4 deposition capacity (both P&lt;0.001). Mannan binding and C4 deposition capacity of MBL in ELBW neonates increased over the first 28 Days, reaching comparative function to full term neonates by D7. Increased mannan binding and C4 deposition was associated with increased oligomerisation of MBL.

Conclusions
Development of functional MBL was delayed in ELBW infants. MBL oligomerisation was associated with increased capacity to activate the complement cascade.
Therapeutic effects of a phospholipase D1 inhibitor against polymicrobial sepsis
Authors: Bae Yoe-Sik , Lee Sung Kyun , Kim Ye Seon , Lee Ha Young 
Published: January 2023

Abstract
In this study, we found that a phospholipase D1-selective inhibitor (VU0155069), significantly increased survival rate against cecal ligation and puncture (CLP)-induced sepsis. Pathological events caused by CLP such as lung inflammation and widespread leukocyte apoptosis were markedly inhibited by the PLD1 inhibitor. The PLD1 inhibitor also strongly inhibited the production of proinflammatory cytokines especially IL-1β in CLP mice and in LPS-stimulated splenocytes. VU0155069 also significantly blocked IL-1β production, caspase-1 activation, and pyroptosis caused by several inflammasome-activating signals (LPS+MSU, NIG, dsDNA) in mouse bone marrow-derived macrophages (BMDM). However, VU0155069 did not affect LPS-induced activation of signaling such as MAPK (ERK, p38 MAPK, JNK), Akt, NF-kB, and NLRP3 expression in BMDM. The PLD1 inhibitor also failed to affect mitochondrial ROS generation and calcium increase caused by LPS or ATP, and subsequent ASC oligomerization caused by several inflammasome-activating signals. The PLD1 inhibitor inhibited caspase-1 activity caused by LPS+NIG in BMDM, which is not a direct effect on caspase-1. Our results suggest that the PLD1 inhibitor shows anti-septic activity as well as inflammasome-inhibiting effects.
Dynamic interaction of PSGL-1 with the T cell receptor regulates the extent of T cell activation
Authors: Otero Dennis C , Ma Jiadai , Bradley Linda 
Published: January 2023

Abstract
We previously identified PSGL-1 (P-selectin glycoprotein-1) as a T cell-intrinsic, cell surface checkpoint inhibitor during chronic viral infection. In this model, we found that cross-linking PSGL-1 with antibody reduced signaling through the T cell receptor (TCR) in exhausted T cells and further upregulated PD-1 expression. However, the function of PSGL-1 in the early activation of naïve T cells has not been fully investigated. We found that, crosslinking PSGL-1 on naïve T cells augments TCR signaling, including enhanced Erk and Akt phosphorylation and Nur77 expression. In addition, T cells expressed more activation markers, including PD-1, proliferated to a greater extent, and secreted more cytokines when PSGL-1 was crosslinked compared to TCR stimulation alone, indicating a role as a costimulatory molecule. Strikingly, we have discovered that PSGL-1 co-localizes with the TCR upon stimulation. CD3 and PSGL-1 can be found in the same micro vesicles following anti-CD3 crosslinking, indicating a close connection between PSGL-1 and the TCR. However, the effects of PSGL-1 ligation are similar to what is seen in T cells that lack PSGL-1 expression, except with respect to PD-1 expression. We propose that decreased induction of PD-1 with PSGL-1 deficiency supports greater effector T cell responses. Further studies will address the function of PSGL-1 in cytoskeletal rearrangement and the formation of the immune synapse. Altogether, these data indicate that the extent of T cell activation is regulated by an association of PSGL-1 with the TCR.
Key roles for the innate immune response to genotoxic stress in neurological disease
Authors: Lukens John R , Bellinger Calli E , Frost Elizabeth L , Shaw Mariah E , Bolte Ashley C , Lammert Catherine R 
Published: January 2023

Abstract
Mounting evidence indicates that DNA damage accumulation in the brain centrally contributes to a number of neurodevelopmental, psychiatric, and neurodegenerative disorders. Yet, little is currently known about the specific molecular pathways that the brain relies on to safeguard itself from DNA insults or how altered regulation of these pathways leads to neurological disease. In recent years, a number of new innate immune signaling pathways that respond to genotoxic stress have been identified. While many of these genomic sensors are highly expressed in the central nervous system (CNS), their roles in CNS homeostasis and disease remain poorly understood. In our recent unpublished studies, we have identified a novel DNA damage sensor that centrally contributes to both neurodevelopmental and neurodegenerative disease. Deletion of this genomic sensor in neurodevelopment was found to cause excessive DNA damage accumulation throughout the brain, abnormal CNS maturation, and the development of motor dysfunction, anxiety, and autism-related behaviors. Moreover, engagement of this DNA damage response in the adult brain was found to drive neurodegenerative disease. Interestingly, we observe that DNA damage-induced cytokine responses are not directly responsible for driving neurological disease in our model. In contrast, our findings using genetic knockout mouse strains, indicate that immune-based genomic sensors influence CNS function and health by regulating cell death signaling. Our studies demonstrate that DNA damage surveillance by the innate immune response coordinates the expulsion of genetically compromised cells from the brain and reveal novel roles for immune-based genomic sensors in CNS disease.
The E3 ligase VHL promotes the differentiation of follicular helper T cells through glycolytic-epigenetic pathways
Authors: Zhu Yangyang , Zhao Yanxia , Aki Daisuke , Liu Yun-Cai 
Published: January 2023

Abstract
Follicular helper T (Tfh) cells are essential for germinal center formation and effective humoral immunity, which undergo different stages of development to become fully polarized. However, the detailed mechanisms of their regulation remain unsolved. Here we found that the E3 ubiquitin ligase VHL was required for Tfh cell development and function upon acute virus infection or antigen immunization. VHL acted through hypoxia-inducible factor (HIF)-1α-dependent glycolysis pathway to positively regulate early Tfh cell initiation. The enhanced glycolytic activity due to VHL deficiency was involved in the epigenetic regulation of ICOS expression, a critical molecule for Tfh cell development. By using the RNAi-based screen, we identified the glycolytic enzyme GAPDH as the key target for the reduced ICOS expression via m6A modification during Tfh cell initiation. Our results thus demonstrated that VHL-HIF-1α axis played an important role during the initiation of Tfh cell development through glycolytic-epigenetic reprogramming. Here we will discuss how immune signals and cell metabolic programs are linked to instruct Tfh cell initiation and function, which can provide some insight into rational vaccine design against human infectious diseases and therapeutic intervention of autoimmune diseases.
Production of qualitatively different antibodies by T-bet+ IgM memory cells and plasmablasts
Authors: Lange Rachel Elizabeth , Levack Russell , King Rodney , Winslow Gary 
Published: January 2023

Abstract
We are investigating the genesis of CD4 T cell-independent T-bet+ IgM+ plasmablasts and memory B cells during intracellular bacterial infection. Although the plasmablasts are generated early during ehrlichial infection, and the memory cells become established within 30 days, it is not known if the populations are related lineally. We showed previously that a high frequency of plasmablast-derived IgM was polyreactive, that is, these IgM bound structurally diverse antigens. Polyreactive IgM were particularly abundant among those Abs that bound the ehrlichial outer membrane protein, OMP-19. Here we addressed whether polyreactivity is also characteristic of memory cell-derived IgM. Antibodies were cloned from sorted CD11c+ T-bet+ IgM memory B cells by single cell Ig sequencing and expressed in HEK cells as chimeric human IgG1. Supernatants were tested by ELISA for reactivity to OMP-19, as well as for double-stranded DNA and insulin. Preliminary data showed that approximately 10% (29 out of 284 samples) of antibodies were OMP-19 specific, but unlike those generated by the plasmablasts, the memory cell-derived antibodies did not exhibit polyreactivity. These data reveal that T-bet+ IgM plasmablasts and memory cells produce distinctly different Igs, which may indicate that the two populations have different origins, or that the populations undergo different selection during their differentiation. Ongoing studies will help resolve these different interpretations.
B cell activation and differentiation employ mTORC1 rather than Xbp1 to initiate distinct segments of the unfolded protein response prior to antibody secretion
Authors: Gaudette Brian M , Jones Derek D , Wilmore Joel R , Allman David 
Published: January 2023

Abstract
Little is known about how activated B cells build biosynthetic pathways and organelle structures needed for subsequent robust antibody secretion. The dominant model holds that newborn plasma cells adapt to increased antibody synthesis by activating the unfolded protein response (UPR) under the control of the transcription factor Xbp1. By analyzing gene expression with either activating or plasma cell-inductive signals we identified qualitatively distinct programs of UPR-affiliated genes preceding the onset of antibody secretion. Genetic loss of function experiments revealed that initial transcription of these loci required the mTORC1 kinase adaptor Raptor, but not Xbp1. Furthermore, single cell RNA-seq analysis of immature and long-lived plasma cells revealed that expression of activation-associated UPR genes correlated with apoptotic gene expression in a subset of plasma cells and in cycling plasma blasts. By contrast, UPR genes associated with true plasma cell induction were expressed broadly across steady state plasma cells including in cells experiencing high levels of pro-survival signaling. We conclude that B cells utilize mTORC1 to activate specialized UPR programs necessary to prepare for and optimize plasma cell function.
Expression of a core gene module of anergy governs maternal CD8+ T cell hypofunction after pregnancy
Authors: Porrett Paige , Xu Rong , Wherry E. John 
Published: January 2023

Abstract
Maternal exposure to fetal antigen during pregnancy results in T cell alloimmunization that impacts immunologic responses later in postpartum life. To study the mechanisms of memory T cell differentiation during pregnancy, we transferred 1x106 CD45.2 OVA-specific OT-1 CD8 T cells into CD45.1 mice. Mice were either 1) mated with Act-mOVA males (pOVA), 2) received an OVA skin graft from an Act-mOVA donor (gOVA) or 3) had no antigen exposure (naïve). Sixty days after cell transfer (~30 days after delivery in pOVA mice and ~30 days after skin graft rejection in gOVA mice), OT-1 cells were recovered for functional, phenotypic, and transcriptional analysis. Whereas gOVA OT-1 T cells differentiated into PD-1intCD127+CD62L+ central memory cells with enhanced recall capacity, pOVA OT-1 T cells persisted as hypofunctional PD-1hi long-lived effectors (CD127-CD62L-). pOVA OT-1 cells were hypoproliferative during recall challenge [Fold expansion over naïve: 4.6 (gOVA) vs. 1.5 (pOVA); p&lt;0.001] and demonstrated impaired cytotoxicity and cytokine production [%IFNγ+TNFα+ = 46±6% (gOVA), vs. 7±6% (pOVA); p&lt;0.001]. Transcriptional profiling using RNA-seq revealed 400 differentially expressed genes (FDR&lt;0.05) between gOVA and pOVA OT-1 T cells; these included anergy-inducing genes such as master regulators of T cell hypofunction (i.e. Tox), repressors of the IL-2 locus (i.e. Aiolos), modulators of calcium responses (i.e. CD38), and enzymes which mediate ubiquitination of signaling molecules of the MAP kinase pathway (i.e. Deltex1). Altogether, pregnancy alloimmunization primes a program of hypofunction in long-lived maternal CD8+ T cell that is shared with other models of anergy.