bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of Germinal Center Reaction against T-Independent Antigens by the Fc(alpha)/(mu)Receptor (53.7)
Authors: Shibuya Akira , Cho Ukiko , Tahara-Hanaoka Satoko , Shibuiya kazuko , Honda Shin-ichiro 
Published: January 2023

Abstract
Germinal center (GC) formation in the secondary lymphoid follicles is induced by immunization with T-independent (TI) as well as T-dependent (TD) antigens. However, structural and functional characteristics of the GC induced by TI antigens have not been elucidated. Here, we show that marginal zone B (MZB) cells and follicular dendritic cells (FDC) preferentially express the Fc receptor for IgM and IgA (Fc(alpha)/(mu)R) as well as the complement receptor CD21/35. Mice deficient in Fc(alpha)/(mu)R showed significantly enhanced GC formation in response to TI antigens, in which both B cells and FDC were involved. Fc(alpha)/(mu)R-deficient mice also showed enhanced TI antigen retention by MZB cells and FDC, CXCL13 expression and affinity maturation of IgG3. Depletion of complements by injection with cobra venom factor completely abrogated this phenotype. These results suggest that Fc(alpha)/(mu)R controls GC reactions and affinity maturation of antibodies against TI antigens by interacting with complement cascades.
Analysis of the in vivo vascular contribution potential of hemato-vascular progenitor cells derived from fetal stages of development (81.1)
Authors: Sánchez Maria José , Garcia Antonio Miguel , Quintero Cristina 
Published: January 2023

Abstract
Hemato-vascular progenitor cells from the adult bone marrow can contribute to blood and vasculature when transplanted into adult irradiated recipient mice. Using this experimental model, high levels of hematopoietic reconstitution can be achieved, while contribution to vasculature is in general very limited. Here we tested if the developmental time of the donor cells and the recipient microenvironment constitute critical factors that determine the extension of contribution to the vasculature.
We have used donor cells from AGM region, fetal liver and adult bone marrow. Cells were obtained from transgenic mice for the SCL-3énh construct that targets vasculature and hematopoietic stem cells, allowing cell lineage tracing in recipient mice. Cells were transferred into the blood stream of adult irradiated and busulfan-treated newborn recipient mice. Using flow cytometry and confocal quantitave microscopy analisys of the liver and kidney vasculature we show that foetal and BM derived progenitor cells contribute similarly to adult vasculature. However, when hemato-vascular progenitor cells are transferered into a new born enviroment, foetal derived cells have a more extended contribution potential to vasculature than adult bone marrow derived cells. This data can have implications for the selection on the donor/receptor ontogenic stage for efficient hemato/vascular transplantation.
Supported by the Spanish Ministry of Education and Science Grant SAF2 07241 and SAF03448/to M.J.S., Junta de Andalucia PAI-CVI 295 supporting grant , Fellowship CONACYT179065 to A.M.G. and fellowhip I3P-CSIC to C.Q.
A Probabilistic Model of Lymphocyte Fate Decisions (81.11)
Authors: Manilay Jennifer O. , Colvin Michael E. 
Published: January 2023

Abstract
New experimental methods for monitoring and manipulating cells down to the single cell level offer vast promise for understanding cell fate decisions in the immune system. An important part of fulfilling this promise will be predictive models of cellular dynamics that can guide experimental interpretation and design. Computational models have been used in stem cell fate studies since Till et al. [PNAS 51:29–36 (1964)] reported a discrete Monte Carlo simulation of stem cell populations that reproduced experimental distributions of proliferative cells in nascent spleen colonies. As part of a combined experimental/computational project to elucidate the regulatory mechanisms underlying T versus B cell development, we have created a probabilistic model of cell differentiation from single common lymphocyte precursors (CLP). In this model, CLP were given probabilities of dividing, death or differentiation that depend on the presence or absence of signaling through the Notch ligand, Delta-1. We used Monte Carlo simulations of 200,000 experiments starting with a single CLP, to predict the resulting distribution of B vs. T cells with different levels of Delta-1. In addition to quantitative predictions to be experimentally tested, this model is a statistical tool for optimal analysis of single cell experiments on differentiating cell populations.
Support: UCM Faculty Startup Funds and DOE (DE-FG02-04ER25625)
Beta-Glucan Induced Mobilization of Hematopoietic Stem Cells Requires Matrix Metalloproteinase-9 (81.8)
Authors: Cramer Daniel , Wagner Stephanie , Li Bing , Liu Jingjing , Hansen Richard , Reca Ryan , Ratajczak Mariusz , Yan Jun 
Published: January 2023

Abstract
Despite advances in stem cell mobilization and techniques, up to 20–25% of patients exhibit poor mobilization and are not able to proceed with auto-transplantation. PGG beta-glucan is a soluble yeast-derived polysaccharide and has been shown previously to induce hematopoietic stem and progenitor cell (HSPC) mobilization. However, the mechanism of action has not been defined. In the current study, we demonstrated that PGG beta-glucan alone was able to mobilize peripheral HSPC at both doses (4.8mg/kg and 9.2mg/kg) after 24 hrs. The combination group (G-CSF/PGG-4.8mg/kg) showed an almost two-fold increase in CFUs compared to the standard of G-CSF alone. Further studies demonstrated that PGG beta-glucan mobilized HSPC via a C or CR3 independent mechanism and did not induce appreciable levels of cytokine secretion. Strikingly, BM cells from PGG beta-glucan mobilized mice secreted abundant matrix metalloproteinase-9 (MMP-9). PGG beta-glucan-induced HSPC mobilization was abrogated in MMP-9 KO mice. Further studies from BM chimeras demonstrated that hematopoietic BM cells and possibly BM endothelial cells stimulated with PGG beta-glucan secreted MMP-9. Taken together, these data suggest that PGG beta-glucan is an agent that enhances HSPC mobilization alone and has a synergistic effect when used in conjunction with G-CSF. This process requires active MMP-9, which results from release of pro-MMP-9 from BM cells.
Regulation of T cell development by the transcription factor HEBAlt (82.1)
Authors: Anderson Michele Kay , Wang Duncheng , Claus Carol L. , Braunstein Marsela , Vaccarelli Giovanna 
Published: January 2023

Abstract
The transcription factor HEBAlt is derived from the HEB gene locus, which also encodes the E2A-related factor HEBCan (Can=canonical). HEBAlt is expressed in early lymphocyte precursors. HEBAlt is synergistically upregulated in T cell precursors by Delta-Notch signaling and HEBCan activity, and ectopic expression of HEBAlt in uncommitted precursors enhances entry into the T cell lineage. By contrast, HEBAlt is only expressed in committed B cell precursors, and expression prior to commitment blocks B cell development. A role for HEBAlt in the repression of CD8alpha transcription at the pro-T cell stage of development is suggested by loss of CD8 in the presence of HEBAlt, and upregulation of CD8 in pro-T cells by an HEBAlt-engrailed repressor construct. HEBAlt can also influence the fate choice between the gamma-delta T cell lineage and the alpha-beta T cell lineage. These results suggest that HEBAlt is important in multiple aspects of early T cell development, including locking in the T/B lineage choice downstream of Notch signaling, repressing T cell-specific genes poised for expression past TCRbeta selection, and influencing an early T cell lineage decision.
Developmental-associated differences in membrane cholesterol content account for the differential responses of transitional immature and mature B cells to B cell receptor engagement (83.1)
Authors: Karnell Fredrick G. , Brezski Randall J. , King Leslie B. , Sanborn Keri B. , Monroe John G. 
Published: January 2023

Abstract
Tolerance-sensitive transitional immature B cells maintain significantly lower membrane unesterified cholesterol levels than mature splenic B cells. In addition, the relatively low level of plasma membrane-associated cholesterol in transitional immature B cells impairs compartmentalization of their B cell receptor (BCR) into cholesterol-enriched domains following BCR aggregation and reduces their ability to sustain certain aspects of BCR signaling as compared with mature B cells. By increasing the level of plasma membrane associated cholesterol in transitional immature B to that seen in mature B cells, we observe an decrease in apoptosis post-BCR stimulation as compared to unmanipulated transitional immature B cells. Furthermore, we have generated a stable genetic mouse model in which cholesterol is constitutively produced in B cells, thus increasing the level of plasma membrane associated cholesterol in transitional immature B cells in vivo. These studies establish an unexpected difference in the lipid composition of peripheral transitional immature and mature B cells and point to a determining role for development-associated differences in cholesterol content for the differential responses of these B cells to BCR engagement.
This work was supported by Training Grant AI055428 and Grants AI43620 and AI32592 from the National Institutes of Health.
GALT development in response to Bacillus anthracis (83.10)
Authors: Severson Kari , Mallozzi Michael , Driks Adam , Knight Katherine L. 
Published: January 2023

Abstract
In several species, including rabbit, a large B cell expansion occurs in GALT in response to the intestinal microbiota. To identify which bacterial species induce GALT development, we injected several species into rabbits with a germ-free appendix, a component of GALT. We found that, when injected alone, the spore-forming Bacillus species, Bacillus anthracis, induces large follicles of proliferating B cells. Our goal is to identify bacterial molecules from B. anthracis that promote GALT development, and determine the mechanism by which these molecules stimulate B cell proliferation.
Previous data suggest that the large B cell expansion in GALT occurs in an antigen-independent, polyclonal manner. Additionally, injection of a known B cell superantigen, Staphylococcus aureus Protein A, into germ-free appendices, was sufficient to induce B cell proliferation. We hypothesize that bacterial molecules act as superantigens and polyclonally stimulate B cells directly through the BCR to induce GALT development. To test this, we probed bacterial lysates with rabbit IgM to search for IgM-binding molecules in B. anthracis. By western blot analysis, we identified a 25kD molecule in B. anthracis spores that binds to rabbit IgM. Experiments are underway to determine the identity of this B. anthracis molecule and to determine if it stimulates GALT development through a superantigen mechanism.
Supported by NIH AI50260
Ligation of TLR9 on lymphoid progenitors promotes dendritic cell production at the expense of lymphopoiesis (83.11)
Authors: Pelayo Rosana , Welner Robert S. , Nagai Yoshinori , Garrett Karla P. , Wuest Todd , Carr Daniel J. , Kincade Paul W. 
Published: January 2023

Abstract
Hematopoietic cells express TLR, raising the possibility that bacterial/viral products influence blood cell formation. We now show that common lymphoid progenitors (CLPs) express functional TLR9, and that dendritic cell production was strongly favored by TLR9 ligation with CpG ODN. TLR9 on CLPs rather than indirect cytokine mediated effects accounted for the shift in dendritic cell production, and CLPs became IL-7 unresponsive in culture. Similarly, CLPs from CpG treated mice had little ability to generate CD19+ cells and augmented competence to produce conventional (cDC), plasmacytoid (pDC) and interferon producing killer dendritic cells (IKDC) even in the absence of TNFα. Finally, lymphopoiesis in mice with active, but not latent HSV-1 infection was very similar to that seen in animals given CpG, and the changes were almost entirely mediated by TLR9. The findings bear on long standing controversies concerning the origins of dendritic cells and show how life-threatening infections may boost their production.
Age dependent decline in CD47 expression on circulating mouse erythrocytes and susceptibility to destruction by macrophages (85.11)
Authors: Khandelwal Sanjay , Saxena Rajiv Krishna 
Published: January 2023

Abstract
We have recently described a novel technique to tag a cohort of mouse erythrocytes released into blood circulation over a defined time window, and follow age related changes in this population in circulation (Khandelwal S and Saxena RK, Expt. Gerontol. 41, 855, 2006). In the current study, we report the kinetics of age dependent decline in CD47 expression on circulating erythrocytes and its role on destruction of senescent erythrocytes by macrophages. CD47 expression was highest on erythrocytes freshly released into circulation and fell steadily thereafter. Oldest erythrocytes in circulation had 30% lower expression of CD47 than the youngest erythrocytes. Depletion of macrophages by administration of clodronate loaded liposomes resulted in a significant fall in the average expression of CD47 on erythrocytes of young (&lt;15 d), intermediate (15–40 d)and old (&gt;40 d) age groups, but a significant increase was observed only in the numbers of old erythrocytes in blood. A time dependent accumulation of CD47low erythrocytes was noted in blood and spleen though the accumulation was markedly higher in spleen. Taken together our results support the proposition that an age dependent fall in CD47 expression on blood erythrocytes may have a role in regulating the destruction of senescent blood erythrocytes by the macrophages.
This work was supported by a research grant from the Department of Science and Technology, Government of India.
Decreases in E2A, AID, and Ig class switch show intrinsic defects in human B cells with age (85.14)
Authors: blomberg bonnie b , landin ana marie , riley richard l , lechner suzanne c , ryan john g , schwartz robert , frasca daniela 
Published: January 2023

Abstract
Elderly human beings have compromised humoral and cellular immune responses, which lead to reduced protection to infectious agents and to vaccines causing protection of only a small proportion of the elderly population. The capacity to class switch the heavy chain of Ig is critical for an effective humoral immune response in mice and humans. We have shown in mice that the E2A-encoded transcription factor E47, which regulates many B cell functions, is down-regulated in old splenic B cells. This leads to a reduction in activation-induced cytidine deaminase (AID) enzyme, which directly induces class switch recombination (CSR) and Ig somatic hypermutatio necessary for affinity maturation of protective Ig. This reduced AID generates less switched antibodies produced by the activated B cells. We have extended our study to investigate whether aging also affects antibody production, E47 and AID expression in B cells isolated from the peripheral blood (PB) of 50 human subjects (18–86 years). Our results obtained with CD19+ B cells show that the expression of E47, AID and Igf×1 circle transcripts progressively decrease with age. We also show an age-related decline in switch memory B cells (IgG+/IgA+/CD27+) and an increase in naive B cells (IgG−/IgA−/CD27−), consistent with our data on the decrease in CSR. Our results provide a possible molecular mechanism for a B cell intrinsic decrease in the humoral immune response with aging and suggest avenues for improvement of vaccine response in elderly humans.
Effects of T-cell derived leptin on thymic function and immune regulation (85.8)
Authors: vandanmagsar bolormaa , Yang Hyunwon , Carter Arnell , Collins Gary , Pyle Robert , Bertak Dorothy , Taub Dennis 
Published: January 2023

Abstract
The communication between the state of systemic and cellular energy balance to the immune compartment is mediated via a complex array of cytokines, hormones and neuropeptides. Leptin is an adipocyte-derived hormone and belongs structurally to the cytokine family including members such IL-2 and IL-12. Leptin signals via a class I cytokine receptor and represents an important link between energy balance on the one side and immune function on the other. Leptin has recently been shown to be produced in limited quantities by murine T cells. To examine the endogenous role of this hormone in the development and control of the adaptive immune responses and inflammation, we have generated T-cell transgenic mice overexpressing leptin. Leptin overexpression in T cells affects thymic size and cellularity and may have considerable impact on the immune function of aging mice. Preliminary data shows that, leptin differentially affects cytokine production by T cells, increasing IL-1, IL-6, IL-12, G-CSF, and MIP-1a levels in leptin transgenic mice compare to wild-type control. More specifically, IFN-g production was significantly higher in older leptin-TG mice, suggesting that endogenously produced leptin may play an important role in the generation of pro-inflammatory Th1 immune responses and thymic development with age.
Leptin Directly Protects Thymus Tissue from Endotoxin-induced Involution (85.9)
Authors: Gruver Amanda Louise , Ventevogel Melissa S , Sempowski Gregory D 
Published: January 2023

Abstract
Thymus tissue produces new T cells and functions well into adulthood. Thymus tissue is highly susceptible to atrophy induced by stress, infections, and ionizing radiation. Prolonged thymus atrophy can contribute to T cell deficiency or prevent immune recovery after acute T cell depletion. No treatment however is currently available to protect against thymus involution. Leptin is a naturally occurring metabolic hormone currently used therapeutically for obesity. We have previously reported that leptin protects against bacterial endotoxin-induced thymus atrophy in a lipopolysaccharide (LPS) mouse model resulting in increased thymus weight, cellularity, and T cell receptor gene rearrangement. We now report the mechanism by which leptin protects the thymus from acute involution. Leptin directly relieves the LPS-induced block on proliferation in CD4−/CD8− thymocytes and protects against stress-induced CD4+/CD8+ thymocyte apoptosis (9% vs. 34% in control, p &lt; 0.01) in a Bcl-2 independent manner. Taken together, these data demonstrate that leptin directly protects against thymus atrophy by promoting expansion of CD4−/CD8− thymocytes and blocking death of CD4+/CD8+ thymocytes. Together, these data support further investigation of leptin as a therapeutic for stimulating thymic function in settings of stress.
Supported by the NIH PO1-HL67314, RO1-AG025150.
TLR agonists induce an alternate pathway for BCR-induced ERK phosphorylation and NF-κB activation (86.9)
Authors: Carter Natalie Annis , Dye John , Palvanov Arkadiy , Rothstein Thomas L 
Published: January 2023

Abstract
The classical pathway for BCR signaling requires signalosome elements including PI-3K, Btk, PLCγ2 and PKCβ. Inhibition or ablation of any of these signaling mediators results in a block in BCR-triggered downstream events such as ERK phosphorylation and NF-κB activation. However, recent work in this lab has demonstrated that exposure to certain molecules such as CD40L and IL-4 produces an alternate pathway such that BCR-induced signaling bypasses the need for signalosome elements. This led us to investigate whether bacterial products that signal “danger” can create an alternate pathway for MAPK activation. We found that BCR-triggered ERK phosphorylation became resistant to the PI-3K inhibitor LY294002 after B cell treatment with LPS, CpG or PAM3CSK. LPS and PAM3CSK were also tested further and found to induce PI-3K independent NF-κB activation recapitulating the alternate pathway induced by CD40L and distinct from that produced by IL-4. Induction of the alternate pathway for BCR signaling by LPS required MyD88. These data demonstrate that TLR agonists induce an alternate pathway for BCR signaling that bypasses essential signalosome elements. This is of special interest considering that high LPS/CpG levels occur during severe gram-negative bacterial infections. This suggests that consideration of the alternate pathway may be prudent when designing treatments for bacterial infections.
Dual Specificity Phosphatase (DUSP) activity regulates ERK activation and positive selection of thymocytes (87.16)
Authors: Bettini Matthew L. , Kersh Gilbert J. 
Published: January 2023

Abstract
Regulation of MAP Kinase phosphorylation is thought to be important for proper translation of TCR signals into thymocyte cell fates. However, the role of phosphatase activity in thymic development has not been extensively characterized. DUSP-6, also known as Map Kinase Phosphatase-3 (MKP-3), is expressed in the thymus and can bind and dephosphorylate ERK. To explore the role of MKP in thymocytes, we expressed MKP-3 or a catalytically inactive form of MKP-3 (DM-MKP3) in an immature thymocyte cell line, 16610 D9. Lower amounts of phosphorylated ERK (p-ERK) were found in D9 cells that over express MKP-3, while D9 cells that over express DM-MKP3 exhibited higher amounts of p-ERK after TCR stimulation in comparison to vector control cells. Thus, over expression of a catalytically inactive ERK phosphatase results in inhibition of all ERK specific MKP activity, and acts as a dominant negative MKP. Utilizing real time PCR, we also observed elevated Egr-1 mRNA levels after TCR stimulation in D9 cells expressing DM-MKP3 compared to control D9 cells. Egr-1 is an ERK dependent immediate early gene known to support positive selection of thymocytes. Finally, we over expressed DM-MKP3 in vivo, and observed enhanced positive selection. Together these results indicate that MKP control of ERK activation after TCR stimulation is critical in regulation of thymocyte cell fate decisions.
This work is funded by grants from the NIH and the ACS.
Generation of Dimers between Itk Molecules, Recruiting Receptors and Substrates (87.23)
Authors: Qi Qian , August Avery 
Published: January 2023

Abstract
Itk is a Tec family of tyrosine kinase that transduces signals from the T cell receptor and other receptors to modulate T cell development and activation. Itk is activated by receptors via a PI3 kinase mediated pathway, which results in recruitment of Itk to the plasma membrane via its PH domain. We show that membrane localization of Itk results in the formation of clusters of at least 2 molecules within 80 angstroms of each other. In addition, only the PH domain, but not the PRR, SH3 or SH2 domain, or kinase activity of Itk, is required for its formation of clusters at the plasma membrane. More importantly, these clusters of Itk molecules form in distinct regions of the plasma membrane since only receptors that recruit PI3 kinase reside in the same membrane vicinity as the recruited Itk. Itk also forms dimers or clusters when associated with the adaptor protein SLP-76. Our results indicate that Itk forms membrane dimers with receptors in specific membrane regions. Furthermore, Itk forms dimers with adaptor proteins that assemble multiprotein complexes.