bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immune reactivity of diabetes-associated human monoclonal autoantibodies defines multiple epitopes and detects two domain boundaries in glutamate decarboxylase.
Authors: Syren K , Lindsay L , Stoehrer B , Jury K , Lühder F , Baekkeskov S , Richter W 
Published: December 2022

Abstract
Autoreactive islet cell Abs (ICA) accompany the pathogenic destruction of pancreatic beta cells in insulin-dependent diabetes mellitus (IDDM). Human monoclonal ICA (MICA 1-6), previously derived from a DR1/DR7-positive newly diagnosed diabetic patient, recognized the islet cell autoantigen glutamate decarboxylase 65 (GAD65) and defined two distinct conformational (MICA 1/3 and MICA 4/6) and one linear (MICA 2) autoimmune epitopes in this molecule. We have isolated 4 new ICA-reactive B cell lines, one from a DR4/DR11-positive newly diagnosed IDDM patient (MICA 7) and three from a DR3 homozygous patient with both IDDM and Graves' disease (MICA 8-10). Like MICA 1-6, MICA 7-10 are specific for GAD65, suggesting that GAD65-reactive B cells dominate the ICA response in IDDM. Comparative analysis of MICA 1-6 and MICA 7-10, using GAD65 mutants and blocking experiments, showed that MICA 7-10 define three novel conformational autoimmune epitopes in GAD65. Further structural analysis of the MICA 1-10 epitopes revealed two distinct and one overlapping region of epitope clusters. Thus, the C-terminal region, defined by amino acids 450 to 570, harbors the conformational MICA1/3 and MICA 7 epitopes as well as the linear epitope of MICA 2 (amino acids 506-531). The MICA 4/6 and MICA 10 epitopes are located in the middle region of the molecule defined by amino acids 245 to 449, whereas the N-terminal region contributes only to the MICA 8/9 epitopes (encompassed in amino acids 39-585). MICA 1-6, 7, and 8-10, derived from three IDDM patients of different HLA haplotypes, define six different epitopes in GAD65 and represent tools to determine the spectrum, possible HLA association, and temporal order of epitope recognition in IDDM.
Neutralizing and infection-enhancing antibody responses do not correlate with the differential pathogenicity of SIVmac239delta3 in adult and infant rhesus monkeys.
Authors: Montefiori D C , Baba T W , Li A , Bilska M , Ruprecht R M 
Published: December 2022

Abstract
Variants of SIV containing a deletion in the nef gene are attenuated in adult macaques, where they provide protection from challenge with pathogenic SIV, but the mechanism of protection remains unknown. One of these attenuated variants carrying deletions in nef, vpr, and NRE (SIVmac239delta3) was recently found to be pathogenic in infant macaques exposed to the virus at birth. We investigated whether inadequate or inappropriate antiviral humoral immune responses could explain why this virus causes disease in infant macaques. Plasma samples from four infants infected with SIVmac251 and five infants and two adults infected with SIVmac239delta3 were evaluated for neutralizing Abs to a laboratory-passaged stock of SIVmac251, an animal challenge stock of SIVmac239/nef-open, and a stock of SIVmac239delta3 to which animals were exposed. Plasma samples were evaluated further for complement-mediated Ab-dependent enhancement (C'-ADE) of SIVmac239/nef-open in vitro. High-titer neutralizing Abs to SIVmac251 were detected in plasma samples from adults and most infants within 3 to 5 wk of infection with either virus. Neutralizing Abs to SIVmac239/nef-open and SIVmac239delta3 developed more slowly, being undetectable before 23 to 63 wk of infection. Timing, magnitude, and breadth of neutralizing Ab responses did not correlate with progression to disease or lack thereof and gave no indication of an impaired humoral immune response in infants. Furthermore, C'-ADE was detected equally in plasma samples from adults and infants. The results indicate that infection with SIVmac239delta3 causes disease in infant macaques despite their mounting of antiviral humoral immune responses comparable to those of adults.
A negatively charged anchor residue promotes high affinity binding to the MHC class II molecule I-Ak.
Authors: Nelson C A , Viner N J , Young S P , Petzold S J , Unanue E R 
Published: December 2022

Abstract
An allele-specific peptide-binding motif for the murine MHC class II molecule I-Ak has proven elusive. Here we demonstrate that the I-Ak molecule preferentially binds peptides that contain negatively charged amino acids at the primary anchor position (Asp or Glu at P1), and that I-Ak can also bind peptides with polar residues at P1 (Cys, Ser, Asn, Gin, or Thr), although with lower affinity. This preference for a negatively charged anchor residue is so pronounced that polyalanine peptides containing a single Asp can bind to I-Ak. Eight naturally processed peptides were found to use an Asp, as demonstrated by a drop in the I-Ak binding affinity of these peptides after Ala substitution. The chemical identity of the amino acid in the anchor position was also important in determining the ability of peptide-I-Ak complexes to resist denaturation on SDS-polyacrylamide gels. The P1 binding pockets of HLA-DR and H-2E molecules are reported to be large and hydrophobic, and these class II molecules prefer to bind peptides with large aliphatic or aromatic side chains at P1. Our results suggest that the structure of the I-Ak P1 binding pocket is different. Based on sequence comparisons, we suggest that the P1 binding pockets of H-2A molecules may prove more polymorphic than the P1 binding pockets of H-2E molecules, and that this additional polymorphism will cause H-2A molecules to display larger intra-allelic differences in peptide binding specificities.
The presentation of class I and class II epitopes of listeriolysin O is regulated by intracellular localization and by intercellular spread of Listeria monocytogenes.
Authors: Hiltbold E M , Safley S A , Ziegler H K 
Published: December 2022

Abstract
The hemolysin, listeriolysin 0 (LLO), produced by Listeria monocytogenes is both a virulence factor and an immunodominant Ag. In this study, we investigated how the lytic activity of LLO effects the context of presentation of two known LLO epitopes by either class I or class II MHC molecules. T cell hybridomas were used to monitor each peptide/MHC ligand. APCs infected with strains of Listeria expressing hemolytic LLO strongly presented the class I MHC epitope; however, this ligand was not well presented by cells infected with nonhemolytic Listeria. In contrast, there was almost no presentation of the class II-binding LLO epitope in cells infected with fully hemolytic Listeria. Only hemolysin-deficient Listeria were presented by class II MHC. Listeria expressing wild-type LLO but deficient in other virulence factors showed a presentation pattern equivalent to that of hemolytic Listeria. To address further the divergence of presentation, we used an intercellular spread assay to detect Ag presentation by cells neighboring the primarily infected one. We found that hemolytic Listeria were presented by both class I and II MHC on cells adjacent to the initially infected one(s). Finally, our kinetic analysis of presentation revealed that the class II ligand is presented over 4 h before the class I ligand. We have demonstrated that LLO's lytic activity potentiates presentation of listerial Ags by class I MHC and inhibits presentation via class II MHC. LLO-mediated intracellular localization (cytoplasmic vs endosomal) of bacteria corresponds to the operative presentation pathway.
Complement activation by a B cell superantigen.
Authors: Kozlowski L M , Soulika A M , Silverman G J , Lambris J D , Levinson A I 
Published: December 2022

Abstract
Staphylococcal protein A (SpA), acting as a B cell superantigen, binds to the Fab region of human VH3+ Igs. Using SpA abrogated of its IgG Fc binding activity (Mod SpA) as a model B cell superantigen, we determined whether such an interaction causes complement activation. Addition of Mod SpA to human serum led to complement consumption and the generation of C3a. To determine whether this complement activation 1) was due to an interaction between VH3+ Igs and the Fab binding site of SpA and 2) proceeded via the classical complement pathway, we tested a panel of monoclonal IgM proteins for the ability to hind C1q following interaction with SpA. C1q binding was restricted to SpA-reactive, VH3+ IgM proteins. To formally determine whether the binding of SpA to the reactive VH3+ IgM proteins led to complement activation, we reconstituted the serum from a hypogammaglobulinemic patient with monoclonal IgM proteins and measured complement consumption and C3a generation following the addition of Mod SpA. We observed complement consumption and C3a production only in Mod SpA-treated serum reconstituted with a VH3+, SpA-binding, IgM protein. Taken together, these results provide compelling evidence that the interaction of the Fab binding site of SpA and VH3+ Igs can lead to complement activation via the classical pathway. This novel interaction may have significant implications for the in vivo properties of a B cell superantigen.
Activation of human eosinophils by IL-13. Induction of CD69 surface antigen, its relationship to messenger RNA expression, and promotion of cellular viability.
Authors: Luttmann W , Knoechel B , Foerster M , Matthys H , Virchow J C , Kroegel C 
Published: December 2022

Abstract
To study the effect of IL-13 on CD69 expression and cell viability in human eosinophils, purified human peripheral blood eosinophils from healthy donors were incubated with increasing concentrations of IL-13. The expression of CD69 was analyzed by flow cytometry (FACS). Surface expression of CD69, which was absent on untreated eosinophils, was induced by IL-13 at concentrations ranging from 1 ng/ml to 1 microgram/ml in a concentration-dependent manner. In contrast, neutrophils expressed CD69 neither spontaneously nor following incubation with IL-13. Semiquantitative reverse transcription-PCR for CD69 mRNA showed constitutive CD69 mRNA expression in purified human eosinophils. Incubation of eosinophils with IL-13 further increased CD69-specific mRNA. Analysis of intracellularly stored CD69 in eosinophils permeabilized with saponin revealed intracellular binding of anti-CD69 Abs in all isolated eosinophils. After stimulation with 100 ng/ml IL-13 for 24 h, the concentration of intracellular CD69 decreased by 41 +/- 9%. Furthermore, IL-13 at a concentration of 100 ng/ml enhanced eosinophil viability, as assessed by propidium iodide staining after 4 days in culture from 8.6 +/- 5.5% in control medium to 50.7 +/- 6.8% following stimulation with IL-13 treatment. The effect of Il-13 on eosinophil viability as well as that on CD69 expression were both neutralized by anti-IL-13 Abs. In conclusion, our results demonstrate that IL-13 specifically activates human eosinophils, as determined by the expression of CD69 cell surface protein and mRNA expression. Furthermore, IL-13 significantly prolongs eosinophil survival in vitro. The data suggest that IL-13 may play a role in the activation of eosinophils.
IL-1 beta activation in human epidermis.
Authors: Nylander-Lundqvist E , Bäck O , Egelrud T 
Published: December 2022

Abstract
IL-1 beta is produced as an inactive 31-kDa precursor processed to active 18-kDa IL-1 beta by proteolytic cleavage, catalyzed by the highly specific IL-1-converting enzyme (ICE). In vitro activation of IL-1 beta can also be obtained by other proteases. Human keratinocytes express IL-1 beta, but not active ICE. The role played by IL-1 beta produced by keratinocytes has therefore been unclear. We asked whether normal human plantar stratum corneum contains biologically active IL-1 beta and, if so, by which mechanism this IL-1 beta is activated. Crude extracts and partially purified preparations from which IL-1 alpha had been removed were used. Biologic IL-1 activity was measured as the ability to induce expression of E-selectin in HUVEC. The crude extract contained IL-1-like activity that could be partially abolished with Abs to IL-1 alpha or IL-1 beta and totally inhibited with a mixture of the two Abs. IL-1 activity in the partially purified preparation was totally inhibited by Abs to IL-1 beta. The specific IL-1 beta activity in the two preparations was 60 to 85% of the sp. act. of recombinant human IL-1 beta. IL-1 beta from plantar stratum corneum had a slightly higher molecular mass than recombinant mature IL-1 beta. Its isoelectric point was approximately 6.1 compared with 6.9 for rIL-1 beta. We conclude that human plantar stratum corneum contains biologically active IL-1 beta that has been activated by an alternative mechanism that does not involve ICE. This is, to our knowledge, the first report of an alternative mechanism of IL-1 beta activation occurring in vivo.
The CD5/CD72 receptor system is coexpressed with several functionally relevant counterstructures on human B cells and delivers a critical signaling activity.
Authors: Cerutti A , Trentin L , Zambello R , Sancetta R , Milani A , Tassinari C , Adami F , Agostini C , Semenzato G 
Published: December 2022

Abstract
The CD5 molecule is expressed on T cells and, at a lower density, on a minor B cell subset (CD5+ B cells). The pan-B Ag CD72 was recently identified as the CD5 counterstructure, and several data suggest the involvement of this ligand pair in T-B cell cognate interaction. However, the functional role of CD5 and CD72 molecules within the B cell compartment is still unknown. In this work we studied umbilical cord blood CD5+ B cells (B-1a), adult splenic CD5- B cells (B-2), and CD5+ B cells from patients with chronic lymphocytic leukemia. Flow cytometry analysis and proliferation assays were used to determine 1) the ability of B-1a and B-2 cells to coexpress functionally relevant counterligands other than CD5 and CD72, and 2) the signaling capacity of CD5 and CD72 in terms of B cell activation and proliferation. To this purpose, freshly isolated or preactivated normal and neoplastic B cells were cultured with agonistic anti-CD5 or anti-CD72 mAbs in the presence or the absence of cytokines equipped with B cell activity. Our data demonstrate that CD5 and CD72 molecules are coexpressed with other ligand pairs usually involved in T-B cell cognate interaction on B-1a cells, but not on B-2 cells. CD5 and/or CD72 engagement delivers critical costimulatory signals in B-1a, B-2, and B cells from patients with chronic lymphocytic leukemia, but with different requirements and patterns. Besides suggesting the potential involvement of B-1a lymphocytes in B-B cell interactions during T-independent B cell responses, our results indicate that CD5 and CD72 counterstructures play a functional role in the B cell compartment.
Avidity maturation, repertoire shift, and strain differences in antibodies to bacterial levan, a type 2 thymus-independent polysaccharide antigen.
Authors: Boswell C M , Stein K E 
Published: December 2022

Abstract
Our previous studies of 102 mAb from mice injected with bacterial levan (BL), a beta(2--&gt;6) linked polyfructosan with beta(2--&gt;1) branch points (inulin determinant, In) showed that BALB/c and CBA/Ca mAb differed in VH and VL gene family usage and fine specificity. We now show that BALB/c and CBA/Ca mAb used different VHJ606 germ-line genes in response to BL: V14A in BALB/c and a previously unidentified gene in CBA/Ca. CBA/Ca mice were found to lack the BALB/c V14A gene. Also, we have compared the responses to one (primary, 1 degree) or two (secondary, 2 degrees) injections of polysaccharide. The secondary BALB/c anti-BL panel has been expanded to a total of 22 mAb, and we report here the isotype, fine specificity, and VH/VL usage of the new mAb. Eight of nine primary BALB/c In-binding mAb were germ-line, whereas both secondary BALB/c In-binding mAb that were sequenced differed from the BALB/c germ-line gene V14A. Germ-line primary mAb were low avidity whereas all five secondary mAb and the one non-germ-line primary were high avidity. There was also a repertoire shift from approximately 90% VHJ606/V kappa 11 in primary mAb to only 50% in secondary mAb (p = 0.002). The data presented provide evidence that avidity maturation and repertoire shifts, features usually associated with a memory response to thymus-dependent Ags, also can occur in response to a second immunization with a thymus-independent type 2 polysaccharide Ag.
Structure of the gene encoding the rat T cell ecto-ADP-ribosyltransferase RT6.
Authors: Haag F A , Kuhlenbäumer G , Koch-Nolte F , Wingender E , Thiele H G 
Published: December 2022

Abstract
Cellular functions, such as the cytolytic potential of CTLs, can be regulated by mono-ADP-ribosylation of target proteins. Recently, the T cell differentiation marker RT6 has been shown to possess mono-ADP-ribosyltransferase activity. Defects in RT6 expression coincide with increased susceptibility in animal models for insulin-dependent diabetes mellitus and other autoimmune diseases. We present an analysis of the rat RT6 gene, providing a basis for studying the regulation of this gene in T cells of normal and diabetes-prone rats. It is the first structural analysis of a mammalian mono-ADP-ribosyltransferase gene. The RT6 gene consists of eight exons spanning approximately 20 kb. The proximal four exons encode 5' untranslated region sequences and are found in multiple alternatively spliced variants. Exon 5 encodes the N-terminal signal sequence. An unusually large exon 7 encodes the entire native polypeptide. The final exon 8 encodes the C-terminal signal sequence for glycosylphosphatidylinositol anchor attachment and the 3' untranslated region. Two independent TATA box-containing promoters associated with exons 1 and 2 were identified, and their activity was verified in transient transfection assays. The distal promoter displays elements contained in the regulatory regions of T cell-specific genes, such as ets and ikaros. Analysis of RT6 transcripts showed that this promoter is the major one in adult rat spleen cells. The 3' end of the gene does not display alternative splicing. However, two polyadenylation signals are found in the 3' untranslated region.
Mechanisms of cellular penetration and nuclear localization of an anti-double strand DNA autoantibody.
Authors: Zack D J , Stempniak M , Wong A L , Taylor C , Weisbart R H 
Published: December 2022

Abstract
An anti-dsDNA Ab, mAb 3E10, was identified that bound membranes of fixed human renal tubular cells, penetrated live murine renal tubular cells in vivo, and localized in the cell nucleus. mAb 3E10 binds both dsDNA and an extracellular matrix protein, HP8/HEVIN, expressed in high endothelial venules. Previous studies showed both shared and distinct binding determinants of mAb 3E10 VH for DNA and HP8/HEVIN. To independently assess the requirement of DNA and HP8/HEVIN in cellular penetration, site-directed mutants of mAb 3E10 VH and V kappa were studied for penetrating kidney cell lines. The results showed that residues required for binding DNA, but not HP8/HEVIN, were necessary for Ab penetration, indicating that cellular penetration required the presence of DNA or binding of Ab to a membrane determinant precisely resembling DNA. Ab Fab penetrated cells, indicating that neither the Fc nor multivalent Ab binding is necessary for cellular penetration. Ab synthesized in the cytoplasm as a result of deleting heavy and light chain signal peptides was not translocated to the nucleus, indicating a mechanism distinct from the usual protein nuclear localization signals and suggesting the need for a membrane-mediated pathway or for post-translational modification of the Ab.
Recombinant IL-4 aggravates experimental autoimmune uveoretinitis in rats.
Authors: Ramanathan S , de Kozak Y , Saoudi A , Goureau O , Van der Meide P H , Druet P , Bellon B 
Published: December 2022

Abstract
IL-4 is the critical regulatory cytokine that preferentially promotes a Th2 type of immune response. In certain models of organ-specific autoimmune diseases in which Th1 cells are implicated in the disease process, treatment with IL-4 has been shown to confer protection by deviating the immune response toward a Th2 type. In this study, we addressed the role of IL-4 in experimental autoimmune uveoretinitis, a prototypic Th1-dependent disease induced in susceptible animals following immunization with soluble retinal Ag. Interestingly, treatment of Lewis rats with IL-4 exacerbated experimental autoimmune uveoretinitis, and simultaneous treatment with neutralizing anti-IL-4 Abs attenuated this increase in the severity of the disease. Ex vivo analysis of cytokines produced in response to the immunizing Ag showed an enhancement in the levels of IFN-gamma, TNF-alpha, and nitric oxide following IL-4 treatment. In vitro, IL-4 augmented the production of IFN-gamma by Con A-stimulated splenocytes in a dose-dependent manner. At low concentrations of IL-4, IFN-gamma production was enhanced, while at higher concentrations this production was inhibited. The specificity of the induction of IFN-gamma by IL-4 was confirmed by neutralizing the activity of IL-4 with anti-IL-4. Taken together, the results herein reported demonstrate that IL-4 can induce the production of IFN-gamma and of inflammatory cytokines under certain conditions, and indicate that IL-4 can exert a dose-dependent differential effect on the induction of immune responses and on autoimmunity.
Selective activation of CD8 T cell effector functions by epitope variants of lymphocytic choriomeningitis virus glycoprotein.
Authors: Martin S , Kohler H , Weltzien H U , Leipner C 
Published: December 2022

Abstract
We provide evidence for selective activation of different effector functions of CD8+ T lymphocytes by altered peptide ligands. A T cell epitope from the glycoprotein of lymphocytic choriomeningitis virus (p33-41) and single amino acid variants thereof were used for primary in vitro induction of CTL clones. When the CTL were analyzed for cytotoxicity, proliferation, IFN-gamma production, and Ca2+ mobilization, we found that some of the clones showed activation of only their cytotoxic effector function when stimulated with variants of their inducing peptides. For one clone, cytotoxic reactivity was readily detected to the inducing peptide and three of four variants, but only the former was also able to trigger proliferation, IFN-gamma production, and Ca2+ mobilization. Another clone also revealed this dichotomy, but in this case some of the altered peptide ligands in addition to the inducing peptide were able to stimulate the full spectrum of effector functions, whereas others only stimulated cytotoxicity. A third clone revealed inefficient triggering of some effector functions by the peptide variants. Our data suggest that, as described for CD4 T cells, altered peptide ligands may lead to partial activation of effector functions of CD8 T cells. In addition, ligands with glycine substitutions in potential TCR contact positions induced CTL, which were able to recognize peptides with a variety of amino acids in the former glycine position.