bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutational analysis of the ligand-binding domain of M-T2 protein, the tumor necrosis factor receptor homologue of myxoma virus.
Authors: Schreiber M , McFadden G 
Published: December 2022

Abstract
The myxoma virus-encoded M-T2 protein shares extensive sequence homology with the ligand-binding domains of the TNF receptors (TNFRs) and has been shown to bind and inhibit rabbit TNF-alpha with affinities similar to those of TNF-alpha with cellular receptors. Here we show that M-T2 protein is secreted from infected cells as an N-linked glycoprotein, with both complex and hybrid or high mannose oligosaccharide chains. Since amino acid homology between M-T2 and cellular TNF receptors is limited to the four N-terminal cysteine-rich domains (CRDs), various M-T2 C-terminal truncations were created in recombinant vaccinia virus vectors. C-terminal deletions that include truncations up to the middle of the fourth CRD effectively bound and inhibited rabbit TNF-alpha. In contrast, removal of any one of the first three CRDs resulted in a mutant M-T2 protein incapable of binding or inhibiting rabbit TNF-alpha. The C-terminal portion of M-T2, which is not homologous to the cellular TNFRs, appears to be important for efficient secretion of M-T2 from infected cells, since all the C-terminal truncations, including a truncation removing only the last 24 amino acids, were effectively retained as intracellular proteins that were still capable of binding and inhibiting rabbit TNF-alpha. We conclude that the first three CRDs of M-T2 fulfill the same ligand-binding function as the cellular TNFRs, and the nonhomologous C-terminal region participates in protein trafficking of M-T2 in virus-infected cells.
IFN-gamma-independent production of IL-12 during murine endotoxemia.
Authors: Heinzel F P , Rerko R M , Ahmed F , Hujer A M 
Published: December 2022

Abstract
We examined whether IFN-gamma deficiency alters the in vivo IL-12 response occurring in the mouse model of acute endotoxemia. C57BL/6 IFN-gamma knockout mice (IFN-gamma 0/0) produced as much circulating IL-12 p40 and IL-12 p70 as did IFN-gamma +/+ mice following injection with S. enteritidis LPS, despite sustaining 11-fold reductions in circulating TNF-alpha. Pretreatment of IFN-gamma 0/0 mice with recombinant mouse IFN-gamma (rIFN-gamma) enhanced circulating TNF-alpha by as much as sixfold, but serum IL-12 p40 and IL-12 p70 responses increased by only twofold or less. Compared with IFN-gamma +/+ mice, the spleens of endotoxemic IFN-gamma 0/0 mice generated two- to threefold fewer IL-12 p40-secreting cells following in vitro or in vivo exposure to endotoxin. The addition of rIFN-gamma to IFN-gamma 0/0 splenocyte culture restored normal levels of LPS-stimulated IL-12 p40 production. Removal of Mac-1+ or F4/80+ cells from endotoxin-stimulated spleen reduced both TNF-alpha and IL-12 p40 production, but 33D1+ dendritic cell removal only affected IL-12 synthesis. These data suggest that the aggregate IL-12 p40 and p70 response to endotoxemia in vivo is IFN-gamma-independent and distinct from IFN-gamma-dependent serum TNF-alpha and splenic IL-12 responses. The cellular and/or cytokine basis for the unexpected preservation of IL-12 production in IFN-gamma-deficient mice may be relevant to normal and pathologic immune responses.
Effects of site-directed mutagenesis of basic residues (Arg 94, Lys 95, Lys 99) of lipopolysaccharide (LPS)-binding protein on binding and transfer of LPS and subsequent immune cell activation.
Authors: Lamping N , Hoess A , Yu B , Park T C , Kirschning C J , Pfeil D , Reuter D , Wright S D , Herrmann F , Schumann R R 
Published: December 2022

Abstract
LPS-binding protein (LBP) is a 60-kDa acute phase glycoprotein capable of binding the LPS of Gram-negative bacteria and facilitating its diffusion. This process is thought to be of potential importance in inflammatory reactions and pathogenic states such as septic shock syndrome. Here, we report on the identification of a LPS binding domain within the LBP molecule and on the identification of single amino acids important for binding of LPS by LBP. Several synthetic LBP peptides inhibited LPS-LBP interaction, and amino acids Arg 94 and Lys 95 were centrally located in these inhibitory peptides. LBP mutants with amino acid exchanges within this region were expressed and tested in five different functional assays: binding to immobilized LPS; facilitation of binding of LPS aggregates to monocytes; transfer of LPS monomers from aggregates to soluble CD14; transfer of soluble CD14-bound LPS monomers to high density lipoprotein (HDL); and enhancement of LPS-induced cell activation. The double mutant Glu 94/Glu 95 was completely lacking LPS binding, transfer, and cell stimulatory activity, indicating that the integrity of amino acids 94 and 95 is required for LBP function. While mutations of amino acids Arg 94 or Lys 95 into alanine reduced the LPS binding activity of LBP dramatically, the ability to facilitate binding of LPS aggregates to membrane CD14 at the cell surface was retained. These findings emphasize the distinction between binding of LPS aggregates to cells, which is not associated with cell stimulation, and binding of LPS monomers to CD14, which leads to cell stimulation.
CD44 is a cytotoxic triggering molecule on human polymorphonuclear cells.
Authors: Pericle F , Sconocchia G , Titus J A , Segal D M 
Published: December 2022

Abstract
In this study, we present evidence that CD44 is a cytotoxic triggering molecule on freshly isolated polymorphonuclear cells (PMN). PMN constitutively express high levels of CD44 as determined by FACS analysis, and immunoprecipitation studies using PMN lysates and an anti-CD44 mAb show a band of 80 to 90 kDa that migrates slightly faster than CD44 from PBL. A bispecific Ab consisting of anti-CD44 Fab cross-linked to anti-DNP Fab (anti-CD44(Fab) x anti-DNP(Fab)) induces PMN to lyse DNP-coated tumor cells in an 18-h assay, and this lysis is specifically inhibited by a polyclonal anti-CD44 F(ab')2. A second bispecific Ab, anti-CD16(Fab) x anti-DNP(Fab), that binds to Fc(gamma)RIIIb on PMN does not induce lysis, indicating that the bridging of target cells to PMN per se is not sufficient for killing. Moreover, CD44-directed killing by PMN results in the lysis of bystander cells, suggesting that the mechanisms of tumor cytolysis by CD44-targeted PMN does not require cell-cell contact. Lastly, PMN lyse target cells coated with hyaluronic acid (HA), the principal ligand for CD44, and this cytolytic activity is specifically blocked by the polyclonal anti-CD44 F(ab')2 and by an anti-CD44 mAb. We suggest that the interaction of HA with CD44 on neutrophils might initiate cytotoxic or inflammatory responses in vivo when neutrophils encounter high amounts of HA, for example on tumor cells, or in the extracellular matrix.
Modulation of human platelet-activating factor receptor gene expression by protein kinase C activation.
Authors: Thivierge M , Parent J L , Stankova J , Rola-Pleszczynski M 
Published: December 2022

Abstract
The effect of PMA on early and late regulation of platelet-activating factor receptor (PAF-R) expression was examined in human monocytes. Treatment with 16 nM PMA for 5 min initiated a rapid reduction (50-75%) in [3H]WEB 2086 binding, which was maximal between 5 and 15 min. Scatchard analysis revealed that PMA treatment reduced the number of binding sites to 50% of control cells without an appreciable change in their affinity. In parallel cultures, flow cytometry analysis using anti-PAF-R Abs failed to reveal any significant decrease in the level of PAF-R expression until after 4 h of treatment with PMA. By 24 h, PAF-R expression had declined by 80 to 90%. This PMA-induced down-regulation of surface PAF-R expression was preceded by a rapid down-regulation of PAF-R mRNA expression. PMA-mediated down-regulation could be blocked by the protein kinase C (PKC) inhibitors H-7 and calphostin C. Activation of PKC by the diacylglycerol analogue 1-oleoyl-2-acetylglycerol also resulted in down-regulation of PAF-R mRNA accumulation, whereas the inactive phorbol diester 4alpha-PMA was ineffective. The rapid disappearance of the PAF-R transcripts was associated with decreased stability of receptor mRNA and not with a change in the nuclear transcription rate of the PAF-R gene. These findings indicate that PAF-R gene expression in human leukocytes can be regulated through a PKC-dependent pathway and involves post-transcriptional destabilization of receptor mRNA.
Breaking of B cell tolerance toward a highly conserved self protein.
Authors: Dalum I , Jensen M R , Hindersson P , Elsner H I , Mouritsen S 
Published: December 2022

Abstract
Self proteins are processed and presented by APCs in the same way as foreign proteins. Presentation of fragments derived from self proteins does not, however, lead to Th cell stimulation because of T cell tolerance. In this study, a novel approach was used to investigate whether B cell tolerance toward a self Ag could be due to the absence of this Th cell recognition. The highly conserved nonimmunogenic protein ubiquitin was used as a model protein. Two modified ubiquitin molecules were constructed with ubiquitin segments exchanged either with the T cell epitope, OVA(325-336), which binds to the mouse A(d) MHC class II molecule, or with the T cell epitope, hen egg lysozyme(50-61), which binds to the A(k) molecule. Mice were immunized with the resulting proteins. Both modified proteins elicited strong autoantibody responses toward soluble native ubiquitin, demonstrating that insertion of a single foreign T cell epitope can overcome the B cell nonresponsiveness. The T cell regulatory role of one of the inserted foreign T cell epitopes in ubiquitin was studied, and at least two different Th cell specificities were found to operate in the response. The T cells were directed against: 1) the inserted epitope, and 2) a combination of the inserted epitope and parts of the neighboring ubiquitin regions. Therefore, the absence of T cell help seems to be an important reason for B cell tolerance toward self proteins.
Recipient CD8+ cells are responsible for the rapid elimination of allogeneic donor lymphoid cells.
Authors: Fast L D 
Published: December 2022

Abstract
Blood transfusion can result in a variety of immunologic responses, including alloimmunization, transfusion-associated graft-versus-host disease, and immunosuppression that results in increased postoperative infection rate, and can also result in increased survival of allografts. One of the many factors influencing the resulting immunologic responses from a blood transfusion is the persistence of the donor leukocytes. A recent study has shown that almost all (99.9%) allogeneic leukocytes are removed within 2 days following transfusion but did not characterize the mechanism responsible for the rapid removal of allogeneic donor cells. Using a murine model these studies show that it is recipient CD8+ T cells that are responsible for the rapid elimination of allogeneic lymphocytes in naive recipients. Effective elimination was dependent on the donor/recipient combination and required that the donor cells express at least one MHC class I disparity to be recognized by the recipient CD8+ cells and that the donor cells also be able to induce additional responses that were needed by the CD8+ cells to manifest full activity. The perforin pathway was the predominant pathway used by the recipient CD8+ cells to mediate this elimination.
Binding of human complement component C4b-binding protein (C4BP) to Streptococcus pyogenes involves the C4b-binding site.
Authors: Accardo P , Sánchez-Corral P , Criado O , García E , Rodríguez de Córdoba S 
Published: December 2022

Abstract
A key step in the elimination of invading pathogens from the body is the covalent binding of complement proteins C3b and C4b to their surface. However, many pathogens have evolved mechanisms to avoid the complement system of the host. Understanding how these mechanisms work may lead to more efficacious forms of therapy. Here we provide an insight into the molecular basis of how Streptococcus pyogenes binds human plasma C4b-binding protein (hC4BP), a complement regulatory molecule that may decrease C3b and C4b deposition on the streptococcal surface. We show that streptococcal surface molecules bind to a site on hC4BP that is indistinguishable from the C4b binding site. This site involves multiple binding surfaces that span short consensus repeats 1 to 3 of the alpha-chain of hC4BP. We propose that hC4BP is bound to the bacterial surface because the streptococcal surface molecules involved in the interaction mimic human C4b epitopes.
Molecular characterization of Bip 1, a monoclonal antibody that modulates IgE binding to birch pollen allergen, Bet v 1.
Authors: Laffer S , Vangelista L , Steinberger P , Kraft D , Pastore A , Valenta R 
Published: December 2022

Abstract
Bet v 1 and homologous proteins represent major cross-reactive allergens for more than 95% of tree pollen-, fruit-, and vegetable-allergic individuals. To study the interaction of Bet v 1 and the immune system, we characterized a Bet v 1-specific mAb, Bip 1. Soluble rBip 1 Fabs were expressed in Escherichia coli and purified by affinity chromatography using immobilized Bet v 1. Bip 1 Fabs displayed a cross-reactivity to homologous allergens comparable with that of IgE Abs from allergic patients. Preincubation of Bet v 1 with Bip 1 led to an up to fivefold increase of allergic patients' IgE binding to Bet v 1. This enhancement in IgE binding may be interpreted as stabilization of a Bet v 1 state, in which certain IgE epitopes are better applicable. It also shows that allergic patients possess IgE Abs directed against different Bet v 1 conformations. The modulation of Ab binding to a given Ag by other Abs was observed also for human Bet v 1-specific IgG Abs, and may represent a novel mechanism for the regulation of specific humoral immune responses in a complex network.
Humanization of an anti-lymphocyte function-associated antigen (LFA)-1 monoclonal antibody and reengineering of the humanized antibody for binding to rhesus LFA-1.
Authors: Werther W A , Gonzalez T N , O'Connor S J , McCabe S , Chan B , Hotaling T , Champe M , Fox J A , Jardieu P M , Berman P W , Presta L G 
Published: December 2022

Abstract
Lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) is involved in leukocyte adhesion during cellular interactions essential for immunologic responses and inflammation. mAbs against LFA-1 have been shown to inhibit several T cell-dependent immune functions in vitro and prevent graft failure after bone marrow transplantation in vivo. A murine anti-human CD11a mAb, MHM24, has been humanized and shown to prevent adhesion of human T cells to human keratinocytes and the proliferation of T cells in response to nonautologous leukocytes in the mixed lymphocyte response assay. However, of the nonhuman primate CD11a that we tested, the murine and humanized mAbs cross-reacted only with chimpanzee CD11a. To have a mAb available for preclinical studies in rhesus monkeys, the humanized mAb was reengineered to bind to rhesus CD11a by changing four residues in one of the complementarity-determining regions, CDR-H2, in the variable heavy domain. Cloning and molecular modeling of rhesus CD11a I-domain suggested that the changes from Lys197 and/or Arg189 in human CD11a I-domain to Glu197 and Gln189 in rhesus CD11a I-domain may be the reason that rhesus CD11a does not bind to the murine and humanized mAbs.
Glycoinositolphospholipids purified from Trypanosoma cruzi stimulate Ig production in vitro.
Authors: Bento C A , Melo M B , Previato J O , Mendonça-Previato L , Peçanha L M 
Published: December 2022

Abstract
We have investigated the effects of glycoinositolphospholipid (GIPL) purified from Trypanosoma cruzi on murine B cell activation. The GIPL neither stimulated any proliferative response by itself, nor affected the blastogenesis induced by surface IgD cross-linking or LPS. On the other hand, the GIPL significantly stimulated both low and high density B cells to secrete IgM in vitro. The GIPL induced B cells to produce IgM when added in the presence of either the surface Ig cross-linker, anti-delta-dextran, or a combination of IL-4 and IL-5. The T. cruzi-derived GIPL also stimulated Ig class switch to IgG1 in cultures stimulated with GIPL, IL-4, and IL-5. The IgG1 secretion was comparable to that induced by LPS plus IL-4. Production of IgG3 was also detected and the GIPL also potentiated the IgG3 production induced by LPS. The stimulatory effect of the T. cruzi-derived GIPL was mediated mainly by its oligosaccharide moiety. This isolated fraction induced a potent IgM secretory response, compared with a much lower response induced by the isolated GIPL ceramide. Taken together, our data suggest that the stimulatory effect of the T. cruzi-derived GIPL on B cell activation could play a role on the conspicuous Ig production observed during infection of the host with T. cruzi.
Loss of either CD4+ or CD8+ T cells does not affect the magnitude of protective immunity to an intracellular pathogen, Francisella tularensis strain LVS.
Authors: Yee D , Rhinehart-Jones T R , Elkins K L 
Published: December 2022

Abstract
Normal mice readily survive a sublethal intradermal (i.d.) infection with Francisella tularensis live vaccine strain (LVS), a model intracellular bacterium, and are strongly protected against subsequent lethal challenge. However, athymic nu/nu mice, which lack mature alphabeta TCR+ T lymphocytes, succumb to i.d. infection within 30 days. Here we characterize the alphabeta T cell subpopulations necessary for both resolution of i.d. infection and generation of optimal protective immunity to LVS. BALB/cByJ mice treated with anti-CD4 or anti-CD8 Abs before i.d. infection survived and cleared bacteria, and anti-CD4- or anti-CD8-treated immune mice survived a very strong i.p. challenge of 10,000 LD50s. Among mutant mice with targeted gene disruptions (knockouts), CD4-, beta2-microglobulin-deficient (which are also CD8-), and gammadelta TCR- mice all resolved a large sublethal i.d. infection. All CD4- and beta2-microglobulin-deficient mice readily survived subsequent lethal i.p. challenge of 10,000 LD50s, even in the absence of specific IgG Abs, as did most (86%) gammadelta TCR- mice. In contrast, alphabeta TCR- mice or alphabeta + gammadelta TCR- mice died about 35 days after i.d. infection. Depletion of gammadelta+ T cells from alphabeta TCR- mice had no effect on mean time to death from i.d. LVS infection. Therefore alphabeta TCR+ cells are required for protection, but either CD4+ or CD8+ T cells are individually sufficient to resolve a large sublethal i.d. LVS infection and to protect against a maximal secondary lethal challenge. These results emphasize the remarkable plasticity of the alphabeta T cell response in protective immunity to intracellular bacteria.
Lethal synergism between influenza infection and staphylococcal enterotoxin B in mice.
Authors: Zhang W J , Sarawar S , Nguyen P , Daly K , Rehg J E , Doherty P C , Woodland D L , Blackman M A 
Published: December 2022

Abstract
Superantigen hyperactivation of the immune system has variable, sometimes lethal consequences for the host. Here we show that concurrent influenza infection enhanced the effects of the bacterial superantigen staphylococcal enterotoxin B (SEB) in mice. The effect was T cell-dependent, and maximal synergism was observed when SEB was administered 7 days after the virus, a timepoint during infection associated with high viral titers, a vigorous cytotoxic T cell response, and extensive lung pathology. The influenza infection enhanced the SEB-induced cytokine response in terms of higher absolute levels of cytokine, sustained secretion, and localization to the respiratory tract. In particular, TNF and IFN-gamma were implicated in the mechanism of death because their neutralization protected the mice from death, and recombinant IFN-gamma and TNFalpha mimicked the lethal effect of SEB in influenza-infected mice. This lethal synergism between concurrent influenza infection and superantigen exposure points to the danger of secondary bacterial involvement in viral pneumonia, and suggests mechanisms that may contribute to sudden and unexpected death from influenza infection. In addition, these data demonstrate that the in vivo effects of superantigen exposure can be strongly influenced by the immune activation status of the host.
Modulation of natural IgM binding and complement activation by natural IgG antibodies: a role for IgG anti-Gal alpha1-3Gal antibodies.
Authors: Yu P B , Holzknecht Z E , Bruno D , Parker W , Platt J L 
Published: December 2022

Abstract
The most abundant natural IgG Abs in human serum are thought to be Abs specific for Gal alpha1-3Gal, a carbohydrate expressed in lower mammals. IgG Abs specific for Gal alpha1-3Gal have been postulated to contribute to host defense and to participate in the rejection of interspecies organ grafts. Our previous studies indicated, however, that IgM and not IgG anti-Gal alpha1-3Gal Abs activate complement on foreign surfaces, and thus the physiologic role of IgG anti-Gal alpha1-3Gal remains uncertain. We tested whether the IgG anti-Gal alpha1-3Gal in a human serum might in fact compete with IgM for binding and thus modulate complement fixation by IgM. Several lines of evidence suggested such competition might occur. First, the functional avidity of IgG and IgM for Gal alpha1-3Gal on cell surfaces were nearly within the same order of magnitude, and in some sera the molar concentrations of IgG and IgM anti-Gal alpha1-3Gal were comparable. Second, binding of human IgM to Gal alpha1-3Gal on cell surfaces was inversely correlated with the concentration of IgG anti-Gal alpha1-3Gal in serum. Third, combination of IgG and IgM Abs specific for Gal alpha1-3Gal demonstrated direct competition for binding. The presence of IgG anti-Gal alpha1-3Gal, which was predominantly IgG2, attenuated by up to 80% the fixation of C1q mediated by IgM, presumably by competing for antigenic sites recognized by IgM Abs that fix complement. Thus, IgG Abs specific for Gal alpha1-3Gal modulate complement activation by IgM specific for that structure and might in this way modulate the consequences that ensue when human blood is brought into contact with foreign organisms or xenogenic cells.
Inhibition of protein kinase C-mediated CD4 down-regulation by oxidative stress in T lymphocytes.
Authors: Nakamura K , Sasada T , Sono H , Yodoi J 
Published: December 2022

Abstract
The CD4 molecule acts as a receptor for class II MHC molecules to stabilize Ag recognition by the TCR and as a high affinity receptor for HIV-1. In this study, we investigated the effect of oxidative stress on the level of CD4 expression on cultured peripheral blood T lymphocytes (PBL blasts). As previously reported, we observed that the surface CD4 was down-regulated by PMA. Unexpectedly, treatment of PBL blasts with hydrogen peroxide (H2O2) or a sulfhydryl oxidative reagent, diamide, almost completely inhibited PMA-induced CD4 down-regulation, although these oxidants per se did not affect the level of CD4 expression. We next assessed the serine phosphorylation of CD4, which is reported to be an indispensable process for PMA-induced CD4 endocytosis. PMA could induce the serine phosphorylation even in the presence of oxidants. We also found that these oxidants had an additive effect on PMA-induced dissociation between CD4 and p56(lck), which is known to be another necessary step for CD4 endocytosis. These results indicate that in T cells, oxidants inhibit protein kinase C-mediated CD4 down-regulation due to perturbing a signaling process other than the above two steps, implying that oxidative stress may tune the functions of CD4+ T cells and their susceptibility to HIV-1 through the control of CD4 expression.