bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recognition of an MHC Class I-Restricted Antigenic Peptide Can Be Modulated by para-Substitution of Its Buried Tyrosine Residues in a TCR-Specific Manner
Authors: Saito Naoyuki G. , Chang Hsiu-Ching , Paterson Yvonne 
Published: January 2023

Abstract
Conformational dependence of TCR contact residues of the H-2Kb molecule on the two buried tyrosine side chains of the vesicular stomatitis virus (VSV)-8 peptide was investigated by systematic substitutions of the tyrosines with phenylalanine, p-fluorophenylalanine (pFF), or p-bromophenylalanine (pBrF). The results of peptide competition CTL assays revealed that all of the peptide variants, except for the pBrF analogues, had near-native binding to the H-2Kb molecule. Epitope-mapped anti-H-2Kb mAbs detected conformational differences among H-2Kb molecules stabilized with these VSV-8 variants on RMA-S cells. Selective recognition of the VSV-8 analogues was displayed by a panel of three H-2Kb-restricted, anti-VSV-8 TCRs. Thus, these substitutions result in an antigenically significant conformational change of the MHC molecular surface structure at both C and D pockets, and the effect of this change on cognate T cell recognition is dependent on the TCR structure. Our results confirm that the structure of buried peptide side chains can determine the surface conformation of the MHC molecule and demonstrate that even a very subtle structural nuance of the buried side chain can be incorporated into the surface conformation of the MHC molecule. The ability of buried residues to modulate this molecular surface augments the number of residues on the MHC-peptide complex that can be recognized as “foreign” by the CD8+ T cell repertoire and allows for a higher level of antigenic discrimination. This may be an important mechanism to expand the total number of TCR specificities that can respond to a single peptide determinant.
Signaling Through the Lymphotoxin-β Receptor Stimulates HIV-1 Replication Alone and in Cooperation with Soluble or Membrane-Bound TNF-α
Authors: Marshall William L. , Brinkman Brigitta M. N. , Ambrose Christine M. , Pesavento Patricia A. , Uglialoro Adele M. , Teng Edna , Finberg Robert W. , Browning Jeffrey L. , Goldfeld Anne E. 
Published: January 2023

Abstract
The level of ongoing HIV-1 replication within an individual is critical to HIV-1 pathogenesis. Among host immune factors, the cytokine TNF-α has previously been shown to increase HIV-1 replication in various monocyte and T cell model systems. Here, we demonstrate that signaling through the TNF receptor family member, the lymphotoxin-β (LT-β) receptor (LT-βR), also regulates HIV-1 replication. Furthermore, HIV-1 replication is cooperatively stimulated when the distinct LT-βR and TNF receptor systems are simultaneously engaged by their specific ligands. Moreover, in a physiological coculture cellular assay system, we show that membrane-bound TNF-α and LT-α1β2 act virtually identically to their soluble forms in the regulation of HIV-1 replication. Thus, cosignaling via the LT-β and TNF-α receptors is probably involved in the modulation of HIV-1 replication and the subsequent determination of HIV-1 viral burden in monocytes. Intriguingly, surface expression of LT-α1β2 is up-regulated on a T cell line acutely infected with HIV-1, suggesting a positive feedback loop between HIV-1 infection, LT-α1β2 expression, and HIV-1 replication. Given the critical role that LT-α1β2 plays in lymphoid architecture, we speculate that LT-α1β2 may be involved in HIV-associated abnormalities of the lymphoid organs.
Covalent Linkage to β2-Microglobulin Enhances the MHC Stability and Antigenicity of Suboptimal CTL Epitopes
Authors: Uger Robert A. , Chan Steven M. , Barber Brian H. 
Published: January 2023

Abstract
Many CTL epitopes of clinical importance, particularly those derived from tumor Ags, display relatively poor MHC binding affinity and stability. Because in vivo immunogenicity, and thus the efficacy of peptide-based vaccines, is thought to be determined by MHC/peptide complex stability, there is a need to develop a simple strategy for enhancing the binding of suboptimal epitopes. Toward this goal, the ability to enhance suboptimal peptides through covalent linkage to β2-microglobulin (β2m) was explored. Two suboptimal variants of a high-affinity Db-restricted influenza nucleoprotein peptide were covalently linked, via a polypeptide spacer, to the amino terminus of human β2m and the recombinant fusion proteins expressed in Escherichia coli. When compared with their uncoupled counterparts, the β2m-linked epitopes display enhanced MHC stabilization and antigenicity. Thus, tethering epitopes to β2m provides a simple method for augmenting the biological activity of suboptimal peptides and could be useful in the design of peptide-based vaccines or immunotherapeutics.
Evidence That the Igκ Gene MAR Regulates the Probability of Premature V-J Joining and Somatic Hypermutation
Authors: Yi Ming , Wu Peiqing , Trevorrow Kenneth W. , Claflin Latham , Garrard William T. 
Published: January 2023

Abstract
The Igκ gene contains an evolutionarily conserved nuclear matrix association region (MAR) adjacent to the intronic enhancer. To test for the function of this MAR, we created mouse lines with a targeted MAR deletion. In MAR knockout animals, the immune system was normal in nearly all respects, including the distributions of various B cell populations and Ab levels. However, in pro-B cells, enhanced rearrangement was noted on the MAR− allele in heterozygotes. In addition, the efficiencies for targeting and generating somatic mutations were reduced on MAR-deleted alleles. These results provide evidence for the MAR negatively regulating the probability of premature rearrangement and positively regulating the probability of somatic hypermutation.
Fine Specificity of Ligand-Binding Domain 1 in the Polymeric Ig Receptor: Importance of the CDR2-Containing Region for IgM Interaction
Authors: Røe Målfrid , Norderhaug Inger N. , Brandtzaeg Per , Johansen Finn-Eirik 
Published: January 2023

AbstractThe human polymeric Ig receptor (pIgR), also called transmembrane secretory component, is expressed basolaterally on exocrine epithelia, and mediates specific external transport of dimeric IgA and pentameric IgM. The extracellular part of pIgR consists of five Ig-like domains (D1-D5), and a highly conserved D1 region appears to mediate the initial noncovalent ligand interaction. While the human pIgR binds both dimeric IgA and pentameric IgM with high affinity, the rabbit counterpart has virtually no binding capacity for pentameric IgM. This remarkable disparity constitutes evidence that the binding site of the two ligands differs with regard to essential receptor contact elements. Therefore, we expressed human/rabbit chimeric pIgRs in Madin-Darby canine kidney cells and found that human pIgR D1 is crucial for the interaction with pentameric IgM when placed in the context of a full-length receptor regardless of its backbone species. D1 contains three complementarity-determining region-like loops (CDR1–3), and to further map human D1 regions involved in pentameric IgM binding, we transfected Madin-Darby canine kidney cells with human/rabbit chimeric receptors in which the regions containing the CDR-like loops had been interchanged. Our results showed that the region containing the CDR2-like loop is the most essential for pentameric IgM binding. The region containing the CDR1-like loop also contributed substantially to this interaction, whereas only little contribution was provided by the region containing the CDR3-like loop, although it appeared to be necessary for maximal pentameric IgM binding.
TRAIL (Apo-2L) and TRAIL Receptors in Human Placentas: Implications for Immune Privilege
Authors: Phillips Teresa A. , Ni Jian , Pan Guohua , Ruben Steven M. , Wei Ying-Fei , Pace Judith L. , Hunt Joan S. 
Published: January 2023

AbstractMechanisms accounting for protection of the fetal semiallograft from maternal immune cells remain incompletely understood. In other contexts, interactions between TRAIL (TNF-related apoptosis-inducing ligand/Apo-2L) and its receptors kill activated lymphocytes. The purpose of this study was therefore to investigate the potential of the TRAIL/TRAIL-R system to protect the placenta against immune cell attack. Analysis by Northern blotting demonstrated mRNAs encoding TRAIL as well as the four TRAIL receptors (DR4, DR5, DcR1/TRID, DcR2/TRUNDD) in human placentas. Immunohistochemical experiments demonstrated that TRAIL protein is prominent in syncytiotrophoblast, an uninterrupted placental cell layer that is continuously exposed to maternal blood, as well as in macrophage-like placental mesenchymal cells (Hofbauer cells). Studies on cell lines representing trophoblasts (Jar, JEG-3 cells) and macrophages (U937, THP-1 cells) showed that both lineages contained TRAIL mRNA and that steady state levels of transcripts were increased 2- to 11-fold by IFN-γ. By contrast, cell lineage-specific differences were observed in expression of the TRAIL-R genes. Although all four lines contained mRNA encoding the apoptosis-inducing DR5 receptor, only trophoblast cells contained mRNA encoding the DcR1 decoy receptor and only macrophages contained DcR2 decoy receptor transcripts. DR4 mRNA was present only in THP-1 cells and was the only TRAIL-R transcript increased by IFN-γ. Cytotoxicity assays revealed that the two trophoblast cell lines were resistant, whereas the two macrophage lines were partially susceptible to killing by rTRAIL. Collectively, the results are consistent with a role for the TRAIL/TRAIL-R system in the establishment of placental immune privilege.
Fas-Independent Cytotoxicity Mediated by Human CD4+ CTL Directed Against Herpes Simplex Virus-Infected Cells
Authors: Yasukawa Masaki , Ohminami Hideki , Yakushijin Yoshihiro , Arai Junko , Hasegawa Atsuhiko , Ishida Yasushi , Fujita Shigeru 
Published: January 2023

Abstract
The present study was undertaken to clarify the mechanisms of cytotoxicity mediated by virus-specific human CD4+ CTLs using the lymphocytes of family members with a Fas gene mutation. CD4+ CTL bulk lines and clones directed against HSV-infected cells were established from lymphocytes of a patient with a homozygous Fas gene mutation and of the patient’s mother. HSV-specific CD4+ CTLs generated from lymphocytes of the patient and her mother exerted cytotoxicity against HSV-infected cells from the patient (Fas−/−) and from her mother (Fas+/−) to almost the same degree in an HLA class II-restricted manner. mRNAs for the major mediators of CTL cytotoxicity, Fas ligand, perforin, and granzyme B, were detected in these CD4+ CTLs using the RT-PCR and flow cytometry. The cytotoxicity of the HSV-specific CD4+ CTLs appeared to be Ca2+-dependent and was almost completely inhibited by concanamycin A, a potent inhibitor of the perforin-based cytotoxic pathway. Although the Fas/Fas ligand system has been reported to be the most important mechanism for CD4+ CTL-mediated cytotoxicity in the murine system, the present findings strongly suggest that granule exocytosis, not the Fas/Fas ligand system, is the main pathway for the cytotoxicity mediated by HSV-specific human CD4+ CTLs.
TNF-α and IL-10 Modulate the Induction of Apoptosis by Virulent Mycobacterium tuberculosis in Murine Macrophages
Authors: Rojas Mauricio , Olivier Martin , Gros Philippe , Barrera Luis F. , García Luis F. 
Published: January 2023

Abstract
The Bcg/Nramp1 gene controls early resistance and susceptibility of macrophages to mycobacterial infections. We previously reported that Mycobacterium tuberculosis-infected (Mtb) B10R (Bcgr) and B10S (Bcgs) macrophages differentially produce nitric oxide (NO−), leading to macrophage apoptosis. Since TNF-α and IL-10 have opposite effects on many macrophage functions, we determined the number of cells producing TNF-α and IL-10 in Mtb-infected or purified protein derivative-stimulated B10R and B10S macrophages lines, and Nramp1+/+ and Nramp1−/− peritoneal macrophages and correlated them with Mtb-mediated apoptosis. Mtb infection and purified protein derivative treatment induced more TNF-α+Nramp1+/+ and B10R, and more IL-10+Nramp1−/− and B10S cells. Treatment with mannosylated lipoarabinomannan, which rescues macrophages from Mtb-induced apoptosis, augmented the number of IL-10 B10R+ cells. Anti-TNF-α inhibited apoptosis, diminished NO− production, p53, and caspase 1 activation and increased Bcl-2 expression. In contrast, anti-IL-10 increased caspase 1 activation, p53 expression, and apoptosis, although there was no increment in NO− production. Murine rTNF-α induced apoptosis in noninfected B10R and B10S macrophages that was reversed by murine rIL-10 in a dose-dependent manner with concomitant inhibition of NO− production and caspase 1 activation. NO− and caspase 1 seem to be independently activated in that aminoguanidine did not affect caspase 1 activation and the inhibitor of caspase 1, Tyr-Val-Ala-Asp-acylooxymethylketone, did not block NO− production; however, both treatments inhibited apoptosis. These results show that Mtb activates TNF-α- and IL-10-dependent opposite signals in the induction of macrophage apoptosis and suggest that the TNF-α-IL-10 ratio is controlled by the Nramp1 background of resistance/susceptibility and may account for the balance between apoptosis and macrophage survival.
IL-4- and IL-4 Receptor-Deficient BALB/c Mice Reveal Differences in Susceptibility to Leishmania major Parasite Substrains
Authors: Noben-Trauth Nancy , Paul William E. , Sacks David L. 
Published: January 2023

Abstract
Using genetically pure BALB/c mice deficient in IL-4 (IL-4−/−) or IL-4 receptor α-chain (IL-4Rα−/−), we have observed different disease outcomes to Leishmania major infection depending on the parasite substrain. Infection with L. major LV39 caused progressive, nonhealing ulcers and uncontrolled parasite growth in both IL-4−/− and IL-4Rα−/− mice. In contrast, infection with L. major IR173 was partially controlled in IL-4−/− mice but efficiently controlled in IL-4Rα−/− mice. Both IL-4−/− and IL-4Rα−/− mice infected with either substrain displayed reduced Th2 responses. Surprisingly, IFN-γ secretion was not up-regulated in the mutant mice, even in the IL-4Rα−/− mice, which were resistant to L. major IR173. The lack of increased IFN-γ production suggests that cytokine cross-regulation may not be operating in this model and that the effective ratios of Th1/Th2 cytokines become more indicative of disease outcome. The partial vs complete resistance to IR173 in IL-4−/− or IL-4Rα−/− mice implies that, in addition to IL-4, IL-13 may be involved in disease progression during L. major infection. The results with LV39 infection indicate that yet another unidentified factor is capable of causing susceptibility to L. major in the absence of IL-4 or IL-4 signaling.
Regulation of the Macrophage Vacuolar ATPase and Phagosome-Lysosome Fusion by Histoplasma capsulatum
Authors: Strasser Jane E. , Newman Simon L. , Ciraolo Georgianne M. , Morris Randal E. , Howell Michael L. , Dean Gary E. 
Published: January 2023

Abstract
Histoplasma capsulatum (Hc) maintains a phagosomal pH of about 6.5. This strategy allows Hc to obtain iron from transferrin, and minimize the activity of macrophage (Mø) lysosomal hydrolases. To determine the mechanism of pH regulation, we evaluated the function of the vacuolar ATPase (V-ATPase) in RAW264.7 Mø infected with Hc yeast or the nonpathogenic yeast Saccharomyces cerevisae (Sc). Incubation of Hc-infected Mø with bafilomycin, an inhibitor of the V-ATPase, did not affect the intracellular growth of Hc, nor did it affect the intraphagosomal pH. In contrast, upon addition of bafilomycin, phagosomes containing Sc rapidly changed their pH from 5 to 7. Hc-containing phagosomes had 5-fold less V-ATPase than Sc-containing phagosomes as quantified by immunoelectron microscopy. Furthermore, Hc-containing phagosomes inhibited phagolysosomal fusion as quantified by the presence of acid phosphatase, accumulation of LAMP2, and fusion with rhodamine B-isothiocyanate-labeled dextran-loaded lysosomes. Finally, in Hc-containing phagosomes, uptake of ferritin was equivalent to phagosomes containing Sc, indicating that Hc-containing phagosomes have full access to the early “bulk flow” endocytic pathway. Thus, Hc yeasts inhibit phagolysosomal fusion, inhibit accumulation of the V-ATPase in the phagosome, and actively acidify the phagosomal pH to 6.5 as part of their strategy to survive in Mø phagosomes.
Central Role of Transcription Factor NF-IL6 for Cytokine and Iron-Mediated Regulation of Murine Inducible Nitric Oxide Synthase Expression
Authors: Dlaska Margit , Weiss Günter 
Published: January 2023

Abstract
We have previously shown that iron regulates the transcription of inducible nitric oxide synthase (iNOS). To elucidate the underlying mechanisms we performed a series of transient transfections of murine fibroblast (NIH-3T3) and macrophage-like cells (J774.A1) with reporter plasmids containing the iNOS promoter and deletions thereof. By means of this and subsequent DNase I footprinting analysis we identified a regulatory region between −153 and −142 bp upstream of the transcriptional start site of the iNOS promoter that was sensitive to regulation by iron perturbation. Gel shift and supershift assays revealed that the responsible protein for this observation is NF-IL6, a member of the CCAAT/enhancer binding protein family of transcription factors. Binding of NF-IL6 to its consensus motif within the iNOS promoter was inducible by IFN-γ and/or LPS, was reduced by iron, and was enhanced by the iron chelator desferrioxamine. Introduction of a double mutation into the NF-IL6 binding site (−153/−142) of an iNOS promoter construct resulted in a reduction of IFN-γ/LPS inducibility by &gt;90% and also impaired iron mediated regulation of the iNOS promoter. Our results provide evidence that this NF-IL6 binding site is of central importance for maintaining a high transcriptional rate of the iNOS gene after IFN-γ/LPS stimulation, and that NF-IL6 may cooperate with hypoxia inducible factor-1 in the orchestration of iron-mediated regulation of iNOS.
Mechanisms of Selective Leukocyte Recruitment from Whole Blood on Cytokine-Activated Endothelial Cells Under Flow Conditions
Authors: Patel Kamala D. 
Published: January 2023

AbstractSelective recruitment of eosinophils to sites of allergic and parasitic inflammation involves specific adhesion and activation signals expressed on or presented by stimulated endothelial cells. Here we examined leukocyte recruitment on cytokine-activated HUVEC under flow conditions. We perfused whole blood through a flow chamber to examine mechanisms of selective leukocyte recruitment. Although there was substantial recruitment of leukocytes on TNF-α-stimulated HUVEC, we found no selective accumulation of any particular leukocyte subpopulations. In contrast, fewer leukocytes were recruited to IL-4-stimulated HUVEC, but the recruitment was selective for eosinophils. We examined the role of adhesion molecules in these interactions and found that eosinophil recruitment was completely blocked with an α4 integrin mAb at the shear rates examined. A significant number of neutrophils were also recruited to IL-4-stimulated HUVEC, and these interactions required P-selectin and P-selectin glycoprotein ligand-1. Thus, whole blood perfusion over cytokine-activated endothelium revealed that IL-4-stimulated HUVEC support selective recruitment of eosinophils, whereas TNF-α-stimulated HUVEC lack selectivity for any leukocyte subclass.
Oral Administration of Myelin Basic Protein Is Superior to Myelin in Suppressing Established Relapsing Experimental Autoimmune Encephalomyelitis
Authors: Benson Jacqueline M. , Stuckman Scott S. , Cox Karen L. , Wardrop Richard M. , Gienapp Ingrid E. , Cross Anne H. , Trotter John L. , Whitacre Caroline C. 
Published: January 2023

AbstractOral administration of a myelin component, myelin basic protein (MBP), induces immunological unresponsiveness to CNS Ags and ameliorates murine relapsing experimental autoimmune encephalomyelitis (REAE). However, a recent clinical trial in which multiple sclerosis patients were treated with repeated doses of oral myelin was unsuccessful in reducing disease exacerbations. Therefore, we directly compared the tolerizing capacity of myelin vs MBP during REAE in B10.PL mice. Oral administration of high doses of myelin, either before disease induction or during REAE, did not provide protection from disease or decrease in vitro T cell responses. In contrast, repeated oral administration of high doses of MBP suppressed established disease and MBP-specific T cell proliferation and cytokine responses. The frequency of IL-2-, IFN-γ-, and IL-5-secreting MBP-specific T cells declined with MBP feeding, implicating anergy and/or deletion as the mechanism(s) of oral tolerance after high Ag doses. We have previously shown that the dosage and timing of Ag administration are critical parameters in oral tolerance induction. Studies presented here demonstrate that Ag homogeneity is also important, i.e., homogeneous Ag (MBP) is more effective at inducing oral tolerance than heterogeneous Ag (myelin).
The Role of Environmental Antigens in the Spontaneous Development of Autoimmunity in MRL-lprMice
Authors: Maldonado Michael A. , Kakkanaiah Vellalore , MacDonald Glen C. , Chen Fangqi , Reap Elizabeth A. , Balish Edward , Farkas Walter R. , Jennette J. Charles , Madaio Michael P. , Kotzin Brian L. , Cohen Philip L. , Eisenberg Robert A. 
Published: January 2023

AbstractIt has been proposed that the “normal” stimulation of the immune system that occurs from interactions with environmental stimuli, whether infectious or dietary, is necessary for the initiation and/or continuation of autoimmunity. We tested this hypothesis by deriving a group of MRL-lpr mice into a germfree (GF) environment. At 5 mo of age, no differences between GF and conventional MRL-lpr mice were noted in lymphoproliferation, flow cytometric analysis of lymph node cells (LN), or histologic analysis of the kidneys. Autoantibody levels were comparably elevated in both groups. A second experiment tested the role of residual environmental stimuli by contrasting GF mice fed either a low m.w., ultrafiltered Ag-free (GF-AF) diet or an autoclaved natural ingredient diet (GF-NI). At 4 mo of age, both groups showed extensive lymphoproliferation and aberrant T cell formation, although the GF-AF mice had ∼50% smaller LNs compared with sex-matched GF-NI controls. Autoantibody formation was present in both groups. Histologic analysis of the kidneys revealed that GF-AF mice had much lower levels of nephritis, while immunofluorescence analysis demonstrated no difference in Ig deposits but did reveal a paucity of C3 deposition in the kidneys of GF-AF mice.These data do not support a role for infectious agents in the induction of lymphoproliferation and B cell autoimmunity in MRL-lpr mice. Furthermore, they suggest that autoantibodies do not originate from B cells that were initially committed to exogenous Ags. They do suggest a possible contributory role for dietary exposure in the extent of lymphoproliferation and development of nephritis in this strain.