bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of metabolic pathways in CD4 T memory cell responses of older individuals
Authors: Yanes Rolando E , Goronzy Jorg J 
Published: January 2023

Abstract
Upon activation, T cells enter a developmental program characterized by clonal expansion and effector cell differentiation followed by contraction and survival of long-lived memory T cells. This program is regulated by interplay of activation-induced signaling and metabolic changes. During the proliferative stage, naïve T cells undergo a metabolic switch to glycolysis which provides the molecular substrates to support T cell growth. The subsequent survival of memory T cells is supported by a switch from mTORC activity to AMPK activation and oxidative metabolism. Compared to naïve T cells, memory T cells have increased mitochondrial capacity; activation induced metabolic changes are less well characterized. Recall responses, such as CD4 T responses to influenza vaccination, are compromised in the elderly. Here, we examined whether the regulation of metabolic pathway contribute to this defect. Upon activation, CD4 memory T cells upregulate oxidative phosphorylation as well as glycolysis. Oxidative phosphorylation peaks 48 hours after activation in parallel to increases in mitochondrial mass. Subsequently, it is then sharply downregulated, while increased glycolysis is maintained. While CD4 memory T cell responses in older individuals (&gt;65 years) display appropriate upregulation of glycolysis, they are associated with increased oxidative metabolic activity compared to younger individuals (&lt; 30 years old). Mitochondrial function was superior as documented by increased spare respiratory capacity with normal mitochondrial mass as well as production of ATP and reactive oxygen species. We propose that the increased mitochondrial activity compromises memory T cell function in older individuals.
Membrane sequestration of the mIgG cytoplasmic domain confers a safety trigger mechanism governing the enhanced activation of isotype-switched IgG-B cell receptor
Authors: Chen Xiangjun , Sui Yinqiang , Liu Wanli 
Published: January 2023

Abstract
A hallmark of the adaptive immunity is the memory for previously experienced pathogens. Memory B cells that express the isotype-switched IgG-BCR are in charge of the establishment of the memory IgG antibody response. A trigger safety mechanism is necessary to govern the burst-enhanced activation of a smoking-gun-like IgG-BCR to avoid illegitimate activation. Here, we reported that the specific interaction between positively-charged mIgG cytoplasmic tail (mIgG-tail) and negatively-charged acidic phospholipids of the plasma membrane can sequester the key tyrosine in ITT motif in the membrane hydrophobic core, which help quench mIgG-tail basal level signaling in quiescent B cells. Indeed, we observed that disruption of the interaction in quiescent B cells induced higher basal level phosphorylation of mIgG-tail ITT motif and promoted the survival signal of primary B cell in vivo. Disruption of the interaction also led to excessive recruitment of prominent BCR signaling microclusters into the B cell immunological synapse, more aggressive Ca2+ mobilization and gene expression indicated by Nur77-GFP reporter mice, which ultimately led to hyper-proliferation of primary B cells after antigen engagement. Physiologically, mIgG-tail was released by antigen engagement or Ca2+ mobilization in the initiation of IgG+ B cell activation, which then enhances Ca2+ mobilization, and in turn facilitates more release of mIgG-tail to further enhance memory B cell activation through such a positive feedback mechanism. Conclusively, our findings shed new light on a novel regulatory mechanism of IgG+ memory B cell to balance immunoprotection and immunopathology and provide new perspective of self-tolerance in class-switched IgG+ memory B cells.
Group 3 innate lymphoid cells continuously require the transcription factor GATA-3 after commitment
Authors: Zhong Chao , Cui Kairong , Wilhelm Christoph , Hu Gangqing , Mao Kairui , Belkaid Yasmine , Zhao Keji , Zhu Jinfang 
Published: January 2023

Abstract
We have previously reported that the transcription factor GATA-3 is critical for the development of all interleukin 7 receptor α-chain (IL-7Rα)-expressing innate lymphoid cells (ILCs) from their progenitor. After ILC lineage commitment, GATA-3 is essential for the maintenance and function of group 2 ILCs (ILC2 cells). Moreover, GATA-3 also maintains low expression in other mature ILCs, such as ILC3 cells, but its function is still elusive. We found that GATA-3 regulated the homeostasis of ILC3 cells by controlling IL-7Rα expression. In addition, GATA-3 served an indispensable function for the further development of the NKp46+ ILC3 subset. GATA-3 bound directly to the Rorc locus in ILC3 cells, repressed RORγt expression, and, thus, regulated the balance between the transcription factors T-bet and RORγt during NKp46+ ILC3 development. Whole transcriptome comparison of CCR6+ lymphoid tissue-inducer (LTi) ILC3 and NKp46+ ILC3 subsets from Gata3 sufficient and deficient mice showed that, among NKp46+ ILC3 cells, GATA-3 not only positively regulated genes specific to the NKp46+ ILC3 subset, but also negatively regulated genes specific to LTi ILC3 cells. Furthermore, GATA-3 also bound to the Il22 promoter locus and was required for IL-22 production in both ILC3 subsets. Mice deficient for Gata3 in ILC3 cells succumbed to Citrobacter rodentium infection due to defective IL-22 production. In conclusion, despite its low expression, GATA-3 was required for the homeostasis, development and function of ILC3 subsets.
Toxoplasma gondii infection triggers a long-term defect in the generation and function of naive CD4+ T lymphocytes
Authors: Jankovic Dragana , Kugler David G. , Flomerfelt Francis A. , Costa Diego L. , Laky Karen , Kamenyeva Olena , Mittelstadt Paul R. , Gress Ronald E. , Ashwell Jonathan D. , Sher Alan 
Published: January 2023

Abstract
Since Ag-stimulated naïve T cells either die as effectors or enter the activated/memory pool, continuous egress of new T lymphocytes from thymus is essential for maintenance of peripheral immune homeostasis. Unexpectedly, we found that systemic infection with the protozoan Toxoplasma gondii triggers not only a transient increase in activated CD4+ Th1 cells, but also a profound and persistent reduction in the size of the peripheral naïve CD4+ T cell pool. We further showed that the resulting perturbation in T cell homeostasis is mechanistically associated with parasite-induced thymic atrophy and more specifically with a loss in the architectural integrity of the thymic epithelium. This structural degeneration is accompanied by impaired thymic selection as evidenced by decreased CD5 expression on the few recent thymic emigrants that reach the periphery. The resulting quantitative and qualitative deficiency in naïve CD4+ T cells leads to an immunocompromised state that both promotes chronic toxoplasma infection and leads to decreased resistance to challenge with an unrelated pathogen. Interestingly, the changes in thymic structure and function induced by toxoplasma closely resemble those associated with the thymic involution that occurs during aging suggesting a possible influence of infection-induced alterations in the thymus on immunologic senescence.
This work was supported by the Intramural Research Program of the National Institute of Allergy and Infectious diseases.
New neutrophil models for studying host-fungal pathogen interactions
Authors: Mansour Michael K , Dagher Zeina , Negoro Paige , Martinelli Michelle , Maxcy Katrina , Feliu Marianela , Alashghar Shaden , Carver Alexa , Sykes David B 
Published: January 2023

Abstract
Neutrophils are terminally differentiated phagocytic cells that represent the first line of defense against pathogens. The study of neutrophils in vitro is difficult owing to a short life span. Immortalized cell line models fail to recapitulate all the effector functions of primary cells. Furthermore, the study of murine neutrophil function in vivo is limited by the lack of a model system that can be genetically manipulated (e.g. gene knockout or overexpression) ex vivo. We describe here the development and use of conditionally immortalized granulocyte/macrophage progenitor cells (GMP) capable of unlimited expansion, genetically tractable, and that can be transplanted into mice to study neutrophil function in vivo. These GMP cell lines were derived from UBC-GFP mice by the transduction of an MSCVneo ER-HoxB8 retrovirus such that factor-dependent cell lines emerge in the presence of stem cell factor and b-estradiol (E2). Upon removal of E2 in vitro or transplantation into irradiated recipients, these GMP precursor cell lines differentiate normally to fully functional neutrophils over the course of 4–5 days. Terminal effector function was confirmed by a) flow cytometry, b) phagocytosis, c) superoxide generation, d) transepithelial migration, and e) NET formation. More importantly, these GMP-derived neutrophils were also capable of fungicidal activity. Of particular note, transplantation of these cells into neutropenic mice challenged with lethal dose of the pathogenic yeast C. albicans, showed prolongation of survival. Overall, this model closely recapitulates primary neutrophils, while providing an inexhaustible and genetically tractable supply of cells, a much-needed tool for the study of neutrophil function.
Cellular Basis for Reduced Resistance in DBA/2 Mice to Babesia microti
Authors: Lamisere Hymlaire , Wortis Henry H 
Published: January 2023

Abstract
The protozoan parasites Babesia bovis, divergens and microti infect humans and other mammals via the tick Ixodus Scapularis. Babesia causes a malaria-like hemolytic disease with the most severe cases seen in those who are immunocompromised or over the age of 50. Mice offer the opportunity to understand genetic and age-related differences in resistance to infection. Previously, we showed that two month old DBA/2 mice are less resistant to Babesia than BALB/cByJ. Further, unlike BALB/cByJ mice, 18 month old DBA/2 mice are not able to clear their infections. Cell transfers established that these differences were at least in part due to CD4 T cell intrinsic differences. We hypothesized that DBA’s relative susceptibility might be due to an inability to produce sufficient cytokines. We harvested the splenocytes of infected young BALB/c and DBA/2 mice at days 7 to 24 post infection and measured the percentage and total number of cytokine-producing T cells. BALB/c mice have more CD4 and CD8 T-cells than infected DBA/2 mice. They also have many more cells with cytoplasmic IFN-y, IL-21 and IL-17A. However, the median fluorescence intensity of cytokine staining and the frequencies of cytokine positive cells did not differ between strains. Thus, the absolute difference in cytokine-positive cell numbers was due to the expansion of the activated T cell populations. In vitro activation revealed that in response to anti CD3 antibody, T cells of DBA/2 mice were less responsive. A similar phenotype might explain why individuals over the age of 50 are more susceptible to severe babesiosis.
ICOS:ICOSL suppresses an excessive T cell response in the CNS during chronic T. gondii infection
Authors: O’Brien Carleigh , Harris Tajie H 
Published: January 2023

Abstract
Regulatory T cells have potent suppressive capacity capable of controlling effector T cell responses and limiting immune-mediated pathology. While the importance of Tregs during the immune response to multiple infections has been demonstrated, the specific mechanisms by which these cells suppress immunopathogenic effector responses in the inflamed brain during infection are not yet known. Tregs are present in the brain during toxoplasmic encephalitis, where effector T cells are required to limit parasite replication. Using multiphoton imaging, we find that Tregs associate extensively with CD11c+ APCs in the brain, and we are currently exploring the importance of this interaction for the maintenance of Treg suppressive function. Inducible T cell costimulator (ICOS) is a costimulatory molecule that has been shown to play an important role in generating effector T cell responses to several pathogens. However, the role of the ICOS-ICOS ligand (ICOSL) interaction between Tregs and APCs in modulating an immune response in the CNS remains poorly understood. We have shown that Tregs in the brain express higher levels of ICOS than effector T cells, and blocking this interaction during chronic T. gondii infection leads to increases in effector T cell responses and immune-mediated pathology. Through in vivo imaging, we have also seen that ICOS-ICOSL blockade changes the behavior of Tregs in the brain, suggesting that ICOS is important for maintaining Treg-APC interactions and potentially allows for control of effector immune responses in the CNS. The excessive immune response seen with ICOSL blockade indicates a shift towards immunopathology, suggesting an important role for ICOS for local Treg suppression in the CNS during chronic infection.
Induction and role of elevated extracellular glutamate during chronic Toxoplasma infection in the brain.
Authors: Wilson Emma H. , David Clement N , Landrith Tyler A , Frias Elma S , Fiacco Todd A , Binder Devin K 
Published: January 2023

Abstract
Toxoplasma is a prolific parasite found in a third of the world’s population that resides primarily as cysts within the brain of the infected host. Infection is for life and continuous recruitment of T cells into the brain parenchyma is required to prevent reactivation of the parasite and fatal encephalitis. Disease can therefore occur in immune compromised individuals including HIV/AIDS, transplant recipients and during congenital transmission which can lead to a broad spectrum of neurological abnormalities. T cells that have migrated into the infected brain parenchyma are heterogenous in function in that they exhibit characteristics of effector, effector memory and tissue resident memory phenotypes. The cell intrinsic and the tissue properties that drive such heterogeneity are unknown. We demonstrate that the extracellular environment of the infected brain includes significantly elevated concentrations of glutamate and hypothesize that this acts to drive infiltrating T cell phenotype and function. Our data show T cells in the brain are capable of responding to the presence of extracellular glutamate either by directly using glutamate following uptake or due to its ability to initiate downstream signaling cascades. By manipulating glutamate concentrations in vitro and in vivo we will test the role of glutamate signaling on the phenotype and function of T cells in the infected brain. Decreasing extracellular glutamate concentrations may be a valuable therapeutic tool to limit neuronal pathology under many circumstances including disease caused by Toxoplasma. It is therefore critical to understand the role of glutamate as a signal to infiltrating protective immune cells.
The Candida albicans quorum-sensing molecule, farnesol, remodels the peritoneal cavity microenvironment to promote innate inflammatory responses in mice.
Authors: Hargarten Jessica C , Atkin Audrey L. , Brown Deborah M. 
Published: January 2023

Abstract
Candida albicans is a polymorphic fungus that causes mucosal candidiasis and life threatening, systemic and intra-abdominal disease in immunocompromised and transplant patients. In normal healthy adults, C albicans is maintained as a commensal mainly through the actions of innate cells. Secretion of the quorum-sensing molecule, farnesol, acts as a virulence factor for C. albicans during systemic infection, but is protective in oral models of infection. Despite the clinical importance of intra-abdominal candidiasis with a mortality rate as high as 65%, the role of farnesol in its pathogenesis has not been studied. In ongoing experiments, we found that introduction of farnesol into the peritoneal cavity (PC) of mice remodels the peritoneal microenvironment to promote innate inflammatory responses. Early following intraperitoneal injection, farnesol stimulates the rapid depletion of B cells followed by recruitment of inflammatory macrophages and neutrophils into the PC compared to thioglycollate and control mice. Kinetic analyses of the transcriptional profile of farnesol-elicited cells reveal an early increase in chemokines followed by increased proinflammatory cytokines consistent with macrophage recruitment and activation. In addition, farnesol-elicited macrophages and dendritic cells demonstrate hallmarks of innate immune activation through high surface expression of class II and co-stimulatory molecules.
Current experiments aim to determine the impact of this innate immune recruitment on antifungal defenses and clearance in the PC. Defining the immunostimulatory properties of farnesol will inform development of more appropriate therapeutic strategies for treatment of intra-abdominal Candida infection.
Characterization of the type I IFN response to liver stage infection with genetically attenuated malaria parasite vaccines.
Authors: Minkah Nana K , Sack Brandon K , Miller Jessica L , Vaughan Ashley , Kappe Stefan H 
Published: January 2023

Abstract
Malaria, a disease caused by Plasmodium parasites, kills nearly 600,000 people annually. Inoculated by an infectious mosquito bite, Plasmodium sporozoites travel to the liver and infect hepatocytes. Here, they develop into merozoites that are released into the blood to cause malaria associated mortality and morbidity. No fully protective malaria vaccine exists, but immunizations with genetically attenuated parasites (GAPs) that arrest in the liver confer sterile protection from challenge in mice. Moreover, using a novel super-infection assay, we observed that GAP immunization induces a potent type I IFN response to control liver stage infection. However, the factors required for the induction and propagation of the IFN response, and the influence of this response on adaptive immunity had not been elucidated. To identify the upstream inducers of IFN signaling, we immunized mice with either mosquito debris or GAPs and measured gene expression in hepatocytes by RNA-Seq. 800 genes were significantly upregulated upon GAP immunization, including transcripts for cytosolic RNA and DNA sensors. To examine the influence of the IFN response on adaptive immunity, WT, IRF3−/− and IFNAR−/− mice were immunized with a suboptimal dose of GAP, and challenged 4 weeks later with WT parasite. The immunization regimen elicited sterile protection in 20% of the WT mice, while 100% protection was achieved in IRF3−/− or IFNAR−/− mice. Taken together, the data suggest that hepatocytes utilize RNA and DNA sensors to induce a type I IFN response that is necessary for early control of liver stage infection, yet detrimental to adaptive immunity. Current studies are examining the mechanisms behind the IFN-mediated suppression of adaptive immunity.
TGF-β and NFAT control T cell receptor restimulation-induced cell death of CD4+CD25+Foxp3+ regulatory cells
Authors: Pandiyan Pushpa 
Published: January 2023

Abstract
One of the key questions in the area of immunomodulation is how CD4+CD25+Foxp3+ regulatory cells (Tregs) are controlled. Here we studied how their survival is regulated in the context of T cell Receptor re-stimulation apoptosis. We show that both mouse and human Tregs and iTregs exhibit increased resistance to T cell Receptor restimulation-induced cell death (RICD) compared to conventional CD4+ cells. The enhanced survival was dependent on TGF-β signaling that results in reduced nuclear translocation of nuclear factor of activated T-cells (NFAT), as well as up-regulation of cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (cFLIP) in Tregs. Tregs also showed significantly decreased susceptibility to α-CD3 antibody mediated apoptosis compared to the effector cells in vivo. While ionomycin increased Treg apoptosis, NFAT activation inhibitors reduced the apoptosis levels of effector cells almost to Treg levels, demonstrating that reduced NFAT activity contributes to decreased RICD in Tregs. Finally, RICD resistance in Tregs manifests itself as increased protection of these cells from cell death during mouse oropharyngeal candidiasis (OPC) infection and inflammatory bowel disease (IBD). Protection from cell death was abrogated in the absence of TGF-β signaling in Tregs. Taken together, our data unravel the previously unrecognized role of TGF-β in promoting Treg survival during TCR restimulation, through regulation of multiple pathways involving NFAT and cFLIP in Tregs. This novel mechanism that offers a selective survival advantage to Tregs may have broader ramifications in immune homeostasis during inflammation.
Evaluation of a newly developed assay designed to assess the interaction between α4β7 and MAdCAM
Authors: Doyle Allison , Cicala Claudia , Jelicic Katija , Van Ryk Donald , Ansari Aftab Ahmed , Fauci Anthony S , Arthos James 
Published: January 2023

Abstract
HIV infection is characterized by high-level replication in gut-associated lymphoid tissues (GALT). This occurs in part because α4β7 +/CD4+ T cells are a preferred target of HIV infection. α4β7 functions as a gut homing receptor. Homing is mediated through a specific interaction with MAdCAM that is expressed on the surface of the high-endothelial venules that line the gut. In addition, α4β7 binds to the V2 domain of HIV gp120. In an SIV model of HIV mucosal transmission, an antibody specific for α4β7 +was found to prevent infection, but the underlying mechanism for this protection is not fully understood. We have proposed that signaling through α4β7 + facilitates HIV transmission, and that the protection from infection that we observed may reflect the capacity of the anti-α4β7 mAb we employed to interfere with this signaling. In order to investigate the role of α4β7+ signaling in mucosal transmission, we have employed a newly developed adhesion assay (Peachman and Rao) that measures the interaction between either the V2 domain of HIV gp120 or MAdCAM with cells expressing α4β7. We have used this assay to evaluate small molecules and antibody antagonists of these interactions. We have found that small molecule antagonists that bind to the active site in α4β7 abrogate binding of cells to both MAdCAM and the V2 domain of HIV gp120. In addition, we determined that retinoic acid increases the adhesion of MAdCAM and V2 to α4β7 expressing cells. This assay should aid in the development of novel strategies designed to interfere with the trafficking of α4β7 +cells to GALT and to mucosal transmission of HIV.