bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sequence analysis of anti-AChR antibodies in experimental autoimmune myasthenia gravis.
Authors: Graus Y , Meng F , Vincent A , van Breda Vriesman P , de Baets M 
Published: December 2022

Abstract
Autoantibodies directed against the acetylcholine receptor (AChR) lead to AChR loss and muscular weakness in myasthenia gravis and its experimental model, experimental autoimmune myasthenia gravis (EAMG). The role of different anti-AChR sequences and specificities in the pathogenesis of EAMG was investigated by sequencing a panel of 19 mouse mAbs, previously elicited against Torpedo and human AChR, that bound to at least four different epitope regions. The pathogenicity of eight mAbs that cross-reacted with mouse or rat AChR was tested. EAMG was induced by four mAbs against the main immunogenic region (MIR). Sequence analysis of different anti-AChR specificities showed a large diversity of H and L chain sequences. Highly homologous H chain sequences (&gt; 90%) were found among some mAbs with similar specificities, whereas highly homologous L chain sequences were not restricted to Abs of a particular fine specificity. Sharing of a highly homologous VH gene or an identical DJH region was observed among three of four pathogenic anti-MIR mAbs, obtained by immunization with AChRs from different species. The VH genes of these three pathogenic mAbs were closely related to PC7183 germline genes indicating that some pathogenic Abs may already be present in the germline repertoire.
VH3 family antibodies bind domain D of staphylococcal protein A.
Authors: Roben P W , Salem A N , Silverman G J 
Published: December 2022

Abstract
Staphylococcal protein A (SpA) is a 45-kDa bacterial membrane protein that can interact with either Fc gamma, a constant region portion of IgG, or with the Fab portion that also mediates conventional Ag binding. In recent reports, SpA has been shown to specifically interact with Fab derived from the VH3 family and is little affected by VH CDR3, JH, or light chain usage. To identify a site on SpA responsible for VH3 Fab binding, we cloned and expressed in Escherichia coli the 61 amino acid sequence of SpA that represents domain D, and this small protein exhibited both the VH3 Fab and Fc gamma binding specificities. Surface plasmon resonance measurements demonstrated that domain D and native SpA had the strongest binding interactions with an IgM-kappa encoded by the germline configuration of the VH3 gene VH26c. In contrast, the apparent affinities for Fc gamma binding were at least fivefold weaker. A variant of domain D was also created that is devoid of the three-codon insertion that distinguishes domain D from all other domains in SpA. Although this deletion did not significantly affect the VH3 Fab-mediated SpA binding activity, it did improve the affinity of Fc gamma binding by an order of magnitude. These observations characterize a site on SpA responsible for binding interactions with B cell Ag receptors that are highly analogous to that of superantigens for T cell receptors.
Nitric oxide synthesis in rat peritoneal macrophages is induced by IgE/DNP complexes and cyclic AMP analogues. Evidence in favor of a common signaling mechanism.
Authors: Alonso A , Carvalho J , Alonso-Torre S R , Núñez L , Boscá L , Sánchez Crespo M 
Published: December 2022

Abstract
The production of nitric oxide was studied in rat adherent peritoneal cells stimulated with preformed IgE/DNP-BSA complexes made of IgE obtained from a secreting hybridoma. Stimulation with complexes at equivalence induced both the production of NO and an increased expression of the mRNA of the inducible isoform of NO synthase (iNOS). Production of NO was also elicited by a rabbit polyclonal F(ab')2 anti-CD23 cross-reacting with rat CD23. Because IgE/DNP-BSA complexes did not elicit Ca2+ mobilization and genistein did not influence the production of NO, cyclic AMP was considered as an alternative signaling molecule. Combination of a suboptimal concentration of dibutyryl cyclic AMP and IgE/DNP-BSA complexes showed an additive effect on NO production, whereas this was not observed when the agonists were used at supraoptimal doses. The inhibitor of cyclic AMP-specific phosphodiesterase IV, rolipram, which acts on the enzyme isoform predominantly expressed in inflammatory cells, also induced the production of NO. Furthermore, IgE/DNP-BSA complexes increased intracellular levels of cyclic AMP. Taken together, these data indicate that stimulation of mononuclear phagocytes via the low-affinity receptor Fc epsilon RII or rising intracellular concentrations of cyclic AMP leads to an enhanced expression of iNOS. Evidence in favor of the involvement of cyclic AMP in the signaling pathway linked to Fc epsilon RII is provided by the effect of IgE/DNP-BSA complexes on intracellular cyclic AMP levels and by the additive effect produced by dibutyryl cyclic AMP on NO production elicited by IgE/DNP-BSA complexes.
Matrilysin expression by human mononuclear phagocytes and its regulation by cytokines and hormones.
Authors: Busiek D F , Baragi V , Nehring L C , Parks W C , Welgus H G 
Published: December 2022

Abstract
Matrilysin is a recently described metalloproteinase with strong catalytic activity against a variety of extracellular matrix substrates including proteoglycans, elastin, laminin, fibronectin, gelatin, and entactin. Production of this metalloproteinase appears to be limited only to a few normal human cell types including glandular epithelium, mononuclear phagocytes, and renal mesangial cells. Furthermore, matrilysin expression in vivo has been demonstrated only in glandular epithelium, especially the endometrium. In the process of examining various cutaneous and lung inflammatory disorders for matrilysin expression by immunohistochemistry and in situ hybridization, we occasionally found monocytes within blood vessels and newly extravasated tissue-associated macrophages that exhibited matrilysin production. In specimens characterized by severe inflammation and, in particular, cystic fibrosis, this feature was commonly observed. We therefore studied the production of matrilysin by monocyte-derived macrophages in vitro in response to various physiologic signals such as endotoxin, phagocytosable material, cytokines, and hormones. We found that matrilysin expression was stimulated by LPS and opsonized zymosan. Up-regulation of matrilysin by LPS was PGE2-dependent, because indomethacin blocked production, an effect at least partially reversed by the addition of exogenous prostaglandin. LPS stimulated matrilysin production pretranslationally and, furthermore, when cultured cells were subjected to in situ hybridization after LPS exposure, considerable variability in matrilysin mRNA expression was observed on an individual cell basis, with some cells having strong signal and others being completely negative. We also found that matrilysin biosynthesis was inhibited by the lymphokines IL-4, IL-10, and IFN-gamma. Other cytokines such as IL-1, TNF-alpha, and IL-6 failed to modulate the production of matrilysin. Finally, matrilysin biosynthesis was suppressed by glucocorticoids and retinoids. Our studies indicate that matrilysin is produced in vivo by mononuclear phagocytes and is a highly regulated metalloproteinase whose production can be modified by a variety of physiologic and pharmacologic signals.
Involvement of protein kinase C during taxol-induced activation of murine peritoneal macrophages.
Authors: Jun C D , Choi B M , Kim H M , Chung H T 
Published: December 2022

Abstract
Taxol has been known to block cell division by stabilizing microtubules with promising anticancer activity. However, taxol has distinct cell cycle-independent effects. Recently, this novel drug has been shown to provide a second signal for murine macrophage activation to tumoricidal activity via L-arginine-dependent nitric oxide (NO) synthesis. To investigate the mechanism of taxol-induced NO synthesis, we evaluated the ability of protein kinase C (PKC) inhibitors such as staurosporine (STSN) or polymyxin B to block taxol-induced effects. Taxol alone had only a small effect, whereas taxol in combination with rIFN-gamma markedly increased NO synthesis in a dose-dependent manner. STSN and polymyxin B decreased NO synthesis, which had been induced by rIFN-gamma plus taxol. Furthermore, prolonged incubation of the cells with phorbol ester, which down-regulates PKC activity, abolished synergistic cooperative effect of taxol with rIFN-gamma on NO synthesis. Synergy between IFN-gamma and taxol was mainly dependent on taxol-induced TNF-alpha secretion because not only the increase of inducible NO synthase (iNOS) gene expression by rIFN-gamma plus taxol was associated with the increased expression of TNF-alpha gene but also taxol-induced NO production was decreased by the treatment of anti-murine TNF-alpha neutralizing Abs. STSN and polymyxin B potently inhibited taxol-induced TNF-alpha secretion and TNF-alpha gene expression as well as iNOS gene expression by rIFN-gamma plus taxol. However, rIFN-gamma plus TNF-alpha-induced NO synthesis was not blocked by STSN or polymyxin B. This result indicates that TNF-alpha-induced signaling for induction of NO synthesis is not dependent on PKC activation, and further suggests that the point at which TNF-alpha acts on the NO synthesis from rIFN-gamma-primed macrophages lies next to the point of PKC activation. In conclusion, the present results strongly suggest that the capacity of taxol to increase NO synthesis from rIFN-gamma-primed macrophages is the result of taxol-induced TNF-alpha secretion via the signal transduction pathway of PKC activation.
Increased cell-associated IL-8 in human exudative and A23187-treated peripheral blood neutrophils.
Authors: Kuhns D B , Gallin J I 
Published: December 2022

Abstract
IL-8 is a potent neutrophil chemoattractant that has been detected in high concentrations at acutely inflamed sites in vivo. Many cell types, including peripheral blood neutrophils, produce IL-8 that can be released by a variety of pro-inflammatory stimuli. However, the functional importance of neutrophil IL-8 during exudation is not yet known. We now report that neutrophils, harvested from skin lesions on the forearms of normal human volunteers (exudative neutrophils), expressed 100-fold higher levels of cell-associated IL-8 and spontaneously released up to 50-fold more IL-8 than freshly isolated peripheral blood neutrophils from the same donor. Furthermore, cell-associated IL-8 in peripheral blood neutrophils increased 20-fold during incubation at 37 degrees C in vitro and was increased over 200-fold after treatment with the Ca2+ ionophore A23187. More than 35% of the cell-associated IL-8 could be released by stimulation with either Ca2+ ionophore A23187 or phorbol myristate acetate. IL-8 was localized by sucrose gradient centrifugation to a subcellular fraction of heterogeneous, light membranous organelles. The accumulation of IL-8 within these organelles is inhibited by cycloheximide but not actinomycin D, suggesting that IL-8 accumulation is under translational, rather than transcriptional control. These studies indicate that peripheral blood neutrophils are capable of synthesis of large amounts of IL-8. Subsequent release of IL-8 during exudation may regulate neutrophil migration into sites of inflammation.
Identification and characterization of a novel protein associated with macrophage complement receptor 3.
Authors: Messika E J , Avni O , Gallily R , Yefenof E , Baniyash M 
Published: December 2022

Abstract
CR3 is a member of the beta 2 integrin family which functions as a bidirectional signaling receptor. The CR3 is composed of the alpha (CD11b) and beta (CD18) subunits, which contain a short intracytoplasmic domain devoid of catalytic activity. It was therefore postulated that CR3 is associated with intracellular molecules that link it to the cytoplasmic signal transduction apparatus. However, no direct association between such molecules and CR3 have been identified so far. We searched for CR3 co-associated molecules that might regulate the function of this receptor. For this purpose CR3 was immunoprecipitated from radiolabeled bone marrow macrophages using a combination of anti-CD11b and anti-CD18 mAbs. Two-dimensional isoelectric focusing analysis of the immunoprecipitates revealed the two CR3 subunits and an additional 16-kDa protein with an apparent isoelectric point of 5.1. This protein, designated p16/5.1, was intracellular, monomeric, nonglycosylated and noncovalently associated with CR3 but not with CR4. CR3-associated p16/5.1 was also detected in four of six macrophage lines as well as in thymic large macrophages, all of which express cell-surface CR3. We suggest that p16/5.1 may be involved in CR3-mediated function.
Ligand binding to Fc gamma R induces c-myc-dependent apoptosis in IL-2-stimulated NK cells.
Authors: Azzoni L , Anegon I , Calabretta B , Perussia B 
Published: December 2022

Abstract
The role of signals transduced via Fc gamma RIIIA in the modulation of the proliferative potential of NK cells has been investigated. Fc gamma R stimulation does not induce NK cell proliferation, and inhibits that induced by IL-2, but not by IL-12, as measured by [3H]TdR incorporation, without affecting entrance or progression through cell cycle. The inhibitory effect depends, at least in part, on induced apoptosis of the cells, detected by both light and electron microscopy examination. Fc gamma R stimulation induces apoptosis only in NK cells that have been previously activated by IL-2: this occurs within 3 h from receptor stimulation and is independent from de novo receptor-induced RNA or protein synthesis, but requires receptor-induced activation of protein tyrosine kinases and extracellular Ca2+ influx. IL-2 induces accumulation of c-myc mRNA in NK cells, and treatment of the cells with c-myc antisense oligodeoxyribonucleotides during the IL-2 stimulation phase inhibits the susceptibility to Fc gamma RIIIA-induced cell death, indicating that the induction of sustained levels of this proto-oncogene is necessary for the phenomenon. Thus, a two-step model is suggested for the Fc gamma R-induced apoptosis in IL-2 activated NK cells: the first step involves induced expression of c-myc, and possibly other permissive factors, upon IL-2 prestimulation; the second depends directly on the stimulation of the receptor, independently of additional gene induction. The evidence presented here suggests a mechanism of control of NK cell expansion at the latest stages of Ab-dependent immune responses.
Selective processing of exogenous antigens by antigen-presenting cells with deleted MHC genes.
Authors: Diment S , Shinde S 
Published: December 2022

Abstract
Recently, APCs expressing genes for the alpha- and beta-chains of MHC class II, but not other proteins encoded in the MHC class II locus, have been found to be defective in processing proteins by the MHC class II Ag presentation pathway. Ag presentation of hen egg OVA has been examined in one of these cell lines, T2.Ak. OVA was processed normally by T2.Ak when compared with OVA processed by T1.Ak, a cell line that expresses the MHC genes missing in T2.Ak. By contrast, native hen egg lysozyme (HEL) was not presented as Ag by T2.Ak, which is in agreement with earlier results. Digestion with thiol proteases is important for Ag processing of HEL. We therefore analyzed the expression of these enzymes in T1.Ak and T2.Ak by using a reagent that specifically radiolabels thiol proteases. In these experiments, the repertoire of proteases expressed in the microsomes of T1.Ak was found to be distinct from the repertoire expressed by T2.Ak. Finally, in in vitro digestion experiments, the group of thiol proteases active in T1.Ak microsomes digested HEL differently from the group identified in T2.Ak. These results provide evidence that the defect in Ag presentation that is encoded by MHC genes and manifests itself in defective processing of HEL is not absolute. Further, the mutation in T2.Ak coincides with altered activities of thiol proteases, a class of enzymes involved in processing exogenous Ags.
Fas antigen-mediated DNA fragmentation and apoptotic morphologic changes are regulated by elevated cytosolic Ca2+ level.
Authors: Oshimi Y , Miyazaki S 
Published: December 2022

Abstract
More than 80% of cells of the human B cell line FMO, which expresses the Fas Ag, underwent apoptosis within 2 h after addition of an anti-Fas mAb. Rises in cytosolic Ca2+ concentration ([Ca2+]i) and their effects were investigated by imaging individual cells continuously and introducing Ca2+ chelators to the outside and/or inside of the cell. The typical Ca2+ response consisted of 1) an early [Ca2+]i rise (basal [Ca2+]i, 85 to 110 nM; peak, 140 to 200 nM; duration, 15 to 20 min), 2) sustained elevation of [Ca2+]i at 140 to 150 nM, 3) a second Ca2+ rise (200 to 500 nM, 15 to 30 min) between 1.5 and 2 h, and 4) a large [Ca2+]i rise (1.2 to 2.0 microM) between 2 and 4 h after addition of mAb. Responses 1, 3, and 4 were mainly caused by Ca2+ entry, and response 2 involved intracellular Ca2+ release from stores. Apoptosis could be induced by mAb even in Ca(2+)-deprived external medium. Chelating cytosolic Ca2+ revealed that the [Ca2+]i rise is a prerequisite for fragmentation of DNA and chromatin, and is also necessary for fragmentation of cells. The critical [Ca2+]i was 140 to 150 nM and a sustained [Ca2+]i rise was more effective. A [Ca2+]i rise itself (without mAb) was ineffective. About 20% of mAb-treated cells showed chromatin condensation at the periphery of the nucleus (possibly an earlier stage of nuclear change) and a bubble-like cell shape even when [Ca2+]i was held below 100 nM. Thus, Ca2+ is mobilized immediately after Fas stimulation and functions as a key factor causing advanced apoptotic changes. Response 4 was related to secondary necrosis.
TGF-beta suppression of IFN-gamma-induced class II MHC gene expression does not involve inhibition of phosphorylation of JAK1, JAK2, or signal transducers and activators of transcription, or modification of IFN-gamma enhanced factor X expression.
Authors: Panek R B , Lee Y J , Benveniste E N 
Published: December 2022

Abstract
TGF-beta is a widely expressed immunoregulatory protein that exerts a diverse range of effects on many types of cells. One of the effects of TGF-beta is the inhibition of both constitutive and cytokine-inducible class II MHC gene expression. In this study, we demonstrate that TGF-beta inhibits expression of class II MHC surface protein, mRNA, and promoter activity in primary astrocytes, and that this inhibition is both dose and time dependent. TGF-beta does not act to inhibit IFN-gamma-induced gene expression in a global fashion, as induction of ICAM-1 and IRF-1 gene expression by IFN-gamma is unaffected by treatment with TGF-beta. Furthermore, TGF-beta does not affect events that are involved in IFN-gamma-induced intracellular signaling such as tyrosine phosphorylation of JAK1, JAK2, and STAT1 alpha, nor does it affect IFN-gamma induction of the class II X2 box binding protein IFN-gamma enhanced factor X. We speculate that TGF-beta may be exerting its effects by modulating the expression or function of constitutively expressed factors responsible for regulation of class II MHC gene expression in astrocytes.
Binding of a peptide antigen to multiple HLA alleles allows definition of an A2-like supertype.
Authors: del Guercio M F , Sidney J , Hermanson G , Perez C , Grey H M , Kubo R T , Sette A 
Published: December 2022

Abstract
Direct MHC binding assays with radiolabeled peptides and HLA class I-expressing mammalian cells such as EBV-transformed B cell lines and PHA-activated blasts have been developed. Significant binding of the radiolabeled probe could be obtained if the target cells were preincubated overnight at 26 degrees C in the presence of beta 2-microglobulin. Under these conditions, up to a few percent of the HLA molecules expressed by either cell type could be bound by the labeled peptides. With these assays, the degree of cross-reactivity of the A*0201-restricted hepatitis B virus core 18-27 peptide with other A2 subtypes was examined. It was determined that this peptide epitope also binds the A*0202, A*0205, and A*0206 but not A*0207 subtypes. Inhibition experiments with panels of synthetic peptide analogues underlined the similar ligand specificities of the HLA-A*0201, A*0202, and A*0205 alleles. Analysis of the polymorphic residues that help form the B and F pockets of various HLA alleles allowed prediction of binding of the hepatitis B virus core 18-27 epitope to two other HLA alleles (HLA-A*6802 and A*6901). Thus, it appears that a family of at least six different HLA-A molecules may share overlapping ligand specificities (aliphatic residues in position 2 and at the C termini). These results suggest that broadly cross-reactive peptide epitopes can be identified and greatly enhance the prospective feasibility of peptide-based vaccination approaches.
Fibrosarcoma cells expressing allogeneic MHC Class II antigens induce protective antitumor immunity.
Authors: Leach D R , Callahan G N 
Published: December 2022

Abstract
The initiation of effective immune responses usually requires presentation of Ags by MHC class I and class II molecules. Although most tumors express MHC class I molecules, MHC class II molecule expression is generally limited to specialized APCs. One reason spontaneous tumors may fail to elicit effective immune responses is that tumor Ags are inefficiently presented by APCs, and adequate T cell-mediated help is not generated. To test this hypothesis, we investigated the possibility of enhancing Th cell stimulation by inducing expression of MHC class II molecules on tumor cells. We transfected a murine fibrosarcoma, Sa1N, with the genes encoding allogeneic (I-Ad) or syngeneic (I-Ak) MHC class II molecules. We then compared the tumorigenic and immunogeneic potential of these transfectants to parental Sa1N tumor cells. Subcutaneous injection of allogeneic or syngeneic transfectants resulted in dramatically fewer tumors than injection of unmodified fibrosarcoma cells, and mice inoculated with MHC class II gene-transfected cells were resistant to subsequent challenge with parental Sa1N cells. Rejection of allogeneic MHC class II Ag+ tumor cells could be mediated by either CD4+ or CD8+ T cells, whereas rejection of secondary challenge with wild-type Sa1N tumor cells required both T cell subsets. These results demonstrate that allogeneic, as well as syngeneic, MHC class II Ag+ tumor cells can stimulate protective antitumor immunity.