bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localization of an Fc-binding reactivity to the constant region of human IgG4. Implications for the pathogenesis of rheumatoid arthritis.
Authors: Zack D J , Stempniak M , Wong A L , Weisbart R H 
Published: December 2022

Abstract
The majority of plasma cells in rheumatoid arthritis (RA) synovium produce rheumatoid factors (RF). IgG RF predominate in the immune complexes found in RA synovial fluid and have been implicated in the pathogenesis of RA. IgG4 RF are a major component of IgG RF produced in serum and synovium of RA patients, even though this subclass comprises only 4% of the serum IgG. We produced an IgG4 mAb, hRF-1, with RF reactivity from the synovial tissue of a patient with RA. mAb hRF-1 had binding specificity for mammalian IgG similar to Staphylococcus aureus protein A, which is characteristic of RF from patients with RA. To determine the molecular basis of this particular RF reactivity, the heavy and light chain genes of mAb hRF-1 were amplified by PCR, cloned, and ligated into the pSG5 plasmid for expression in COS-7 cells. Chain recombination experiments localized the Fc-binding reactivity to the hRF-1 heavy chain. Using a series of chimeric Ab sequences, the Fc-binding reactivity was mapped to the constant region of IgG4 rather than the variable region involved in classic RF reactivity. Multiple domains, including Hinge, CH2, and CH3 of the IgG4 constant region were required for Fc binding. Our studies demonstrate an example of RF-like Fc-binding reactivity that is conferred by the gamma-4 constant region rather than the classic Ag binding site and suggest that increased production of IgG4 may contribute to the pathogenesis of RA.
Defective TCR-mediated signaling in anergic T cells.
Authors: Migita K , Eguchi K , Kawabe Y , Tsukada T , Ichinose Y , Nagataki S , Ochi A 
Published: December 2022

Abstract
Extrathymic T cell tolerance to Ags can be achieved through clonal deletion by activation-induced programmed cell death as well as by functional unresponsiveness (anergy) of Ag reactive-T cells. Previous studies demonstrated that in vivo administration of staphylococcal enterotoxin B (SEB) induces SEB-specific T cell anergy. To investigate the molecular mechanisms of T cell anergy, we analyzed the TCR-mediated signal transduction in normal and anergic T cells. Anergic T cells exhibited impaired protein tyrosine phosphorylation on TCR-mediated stimulation. The altered tyrosine phosphorylation in anergic T cells may be caused by a defect in tyrosine phosphorylation of TCR zeta-chain and its subsequent association with ZAP-70 tyrosine kinase. Our data demonstrated that TCR zeta-chain phosphorylation and its sequential interaction with ZAP-70 are essential for the initiation of TCR-mediated signal transduction.
Differences in the avidity of TCR interactions with a superantigenic ligand affect negative selection but do not allow positive selection.
Authors: Chervonsky A V , Golovkina T V , Ross S R , Janeway C A 
Published: December 2022

Abstract
The products of the sag genes of the exogenous mouse mammary tumor virus (MMTV) genome and of endogenous Mtv integrants have been demonstrated to affect the T cell repertoire in mice by causing the deletion of T cells expressing receptors encoded by particular V beta gene segments. Since these deletions affect large populations of T cells with receptors of heterogeneous specificity, they serve as an important model for the study of T cell development in normal mice. Using several C3H/HeN-based strains that express different MMTV(C3H) transgenes, we demonstrate here that the stage of development at which T cell deletion occurs is determined by the level of ligand expression. Although at low levels of ligand expression in the thymus some signs of activation were observed in immature thymocytes, we were unable to detect a level of Sag expression that led to net positive selection. Moreover, we detected a level of Sag-transgene expression that did not cause negative selection in the thymus; no signs of positive selection were observed either. Inclusion of the env gene in the construct, earlier shown to markedly potentiate stimulation by Sag in mixed lymphocyte reactions, also markedly increased the ability of Sag to drive negative selection. These data are interpreted as showing that marked quantitative differences in expression of superantigens does not reveal a level at which only positive selection occurs. This, in turn, suggests that positive selection will occur on ligands distinct from those that drive clonal deletion.
Mapping the Ig superantigen-binding site of HIV-1 gp120.
Authors: Goodglick L , Zevit N , Neshat M S , Braun J 
Published: December 2022

Abstract
The envelope glycoprotein, gp120, of HIV-1 has recently been identified as a member of the new family of Ig superantigens (Ig-SAg). This classification is based on the selective binding of gp120 to an unusually high proportion of endogenous, nonimmune Ig, and the selective activation of nonimmune B cells by gp120 in vitro. Many, if not all of the nonimmune Ig that bind to gp120 are members of the VH3 Ig gene family. The aim of this study was to determine the epitope on gp120 that was responsible for its Ig-SAg binding activity. To do this, we utilized a panel of 30 peptides derived from gp160 in a competition-binding assay. For five Igs that were tested, as well as for polyclonal serum IgM, two overlapping peptides (each 20 amino acids in length) were identified that were potent inhibitors of gp120 binding. Similarly, the 10 amino acid overlap region of these two peptides had inhibitory activity. Thus, this decamer sequence represented the optimal Ig-SAg epitope or mimotope. The amino acid residue at position 1 of the decamer, and to a lesser extent at position 10, was critical for peptide binding. In addition to this decamer peptide, other peptides that shared modest sequence homology were also selectively inhibitory for specific Ig samples. These findings provide the first definition of an Ig-SAg ligand at the peptide level and will facilitate further structural and biologic characterization of this new class of pathogenic Ags.
Inhibition of expression of cyclin A in human B cells by an immunosuppressant mizoribine.
Authors: Hirohata S , Yanagida T 
Published: December 2022

Abstract
Mizoribine has been used to prevent rejection of organ allografts in humans and in animal models. Recent clinical trials have demonstrated its efficacy in rheumatoid arthritis and lupus nephritis, in which abnormalities of B cell functions are also involved. We therefore examined the effects of mizoribine on the in vitro function of human B cells. IgM production was induced from highly purified B cells obtained from healthy donors by stimulation with Staphylococcus aureus Cowan I (SA) plus IL-2. Mizoribine suppressed the production of IgM at its pharmacologically attainable concentrations (1 to 3 micrograms/ml) in a dose-dependent manner. Mizoribine had to be present within the first 96 h after the initiation of cultures to exert its suppressive effects on B cell responses. Cell cycle analysis disclosed that mizoribine significantly decreased the numbers of B cells in S + G2 + M phases. Mizoribine did not decrease GTP levels in SA-stimulated B cells, whereas mizoribine led to a decrease in GTP levels in activated T cells, which was reversed by addition of GMP. Consistently, the suppressive effects of mizoribine on the IgM production of SA-stimulated B cells was not reversed by the addition of GMP as much as 40 microM, which overcame the inhibitory effects of mizoribine on the proliferation of anti-CD3-stimulated T cells. Although mizoribine did not suppress the expression of CD25 and cdc2 kinase, mizoribine markedly suppressed the expression of cyclin A in SA-activated B cells. These results indicate that mizoribine directly suppresses the function of human B cells without interfering with the initial phase of activation. Moreover, the data demonstrate that mizoribine interferes with the cell cycle progression of activated B cells by suppressing the expression of cyclin A by a mechanism distinct from guanine ribonucleotide depletion.
Listeriolysin is processed efficiently into an MHC class I-associated epitope in Listeria monocytogenes-infected cells.
Authors: Villanueva M S , Sijts A J , Pamer E G 
Published: December 2022

Abstract
Listeria monocytogenes is an intracellular pathogen that enters the cytoplasm of infected cells by secreting listeriolysin (LLO), a protein that destroys the phagosomal membrane. In infected mice, LLO is a major Ag detected by protective, MHC class I-restricted CTLs. Although the role of LLO in pathogenesis and host immunity is well established, its rate of intracellular synthesis has yet to be determined. Herein we show that cytosolic L. monocytogenes secrete LLO at a relatively low rate of approximately one molecule per bacterium per minute. Under extracellular labeling conditions, the rate of LLO secretion is approximately 50-fold higher. Intracellular LLO synthesis suffices, however, for the accumulation of 600 to 1000 H-2Kd-associated LLO 91-99 epitopes per cell. We calculate that between four and 11 LLO molecules are degraded for each LLO 91-99 epitope bound by H-2Kd. Our findings indicate that the antigenicity of LLO, with respect to MHC class I-restricted CTLs, cannot be attributed to high levels of intracellular secretion. Rather, LLO is a dominant Ag because it is rapidly degraded and very efficiently processed into an MHC class I-associated epitope.
Positive selection of thymocytes involves sustained interactions with the thymic microenvironment.
Authors: Wilkinson R W , Anderson G , Owen J J , Jenkinson E J 
Published: December 2022

Abstract
CD4+8+ cortical thymocytes are critically dependent upon interaction with the thymic epithelium to undergo positive selection and maturation into single-positive CD4+ or CD8+ cells. Here we investigate further the nature of this interaction and provide evidence that positive selection requires sustained, rather than "single hit," interaction with thymic stromal cells. We also show that calcineurin-mediated signaling in thymocytes is required for the initial stages of positive selection, but is not essential throughout the period of thymocyte dependence on stromal cell contact during positive selection. In addition, we show that double-positive thymocytes that have initiated positive selection (CD69+4+8+) and newly generated single-positive (CD69+4+) cells differ markedly in response to the same stimulus through the TCR. The former undergo deletion, whereas the latter proliferate, indicating that a critical change in response to TCR ligation occurs within the narrow developmental window between these two stages.
Nuclear factor-IL6 activates the human IL-4 promoter in T cells.
Authors: Davydov I V , Krammer P H , Li-Weber M 
Published: December 2022

Abstract
Positive regulatory element I (PRE-I) is a strong enhancer element essential for expression of the human IL-4 gene. To identify transcription factors binding to PRE-I, we screened a cDNA expression library from Jurkat T cells and isolated a cDNA encoding nuclear factor (NF)-IL6 (also known as C/EBP beta). NF-IL6 mRNA was found in human Jurkat T cells and in the mouse Th2 clone D10, but not in Th1 clone 29. rNF-IL6 expressed in bacteria was shown to specifically bind to PRE-I. PRE-I forms multiple DNA-protein complexes with nuclear extracts from Jurkat cells. Some of these complexes were demonstrated to contain NF-IL6 by using anti-C/EBP beta Abs. Overexpression of NF-IL6 enhanced expression of the chloramphenicol acetyl transferase reporter gene linked to the PRE-I-thymidine kinase or the human IL-4 promoter more than 10-fold in Jurkat cells. Promoter deletion studies revealed two additional NF-IL6 binding sites located at positions -44 to -36 (C/EBP proximal) and -87 to -79 (C/EBP medial), respectively. Our results demonstrate that NF-IL6 is involved in transcriptional activation of the human IL-4 promoter in T cells.
Molecular characterization of two murine eosinophil beta chemokine receptors.
Authors: Post T W , Bozic C R , Rothenberg M E , Luster A D , Gerard N , Gerard C 
Published: December 2022

Abstract
beta or C-C chemokines including RANTES, MCP-3, MIP-1 alpha, and eotaxin have been implicated in the pathogenesis of eosinophilic inflammation. Two human beta chemokine receptors have been cloned and characterized: the MIP-1 alpha/RANTES receptor or C-C chemokine receptor 1 (CCR-1) and the MCP-1 receptor or C-C chemokine receptor 2 (CCR-2). However, no murine beta chemokine receptors have thus far been reported. Molecular cloning from mouse genomic DNA and cDNA libraries yielded two murine beta chemokine receptors with 79% and 65% sequence identity with human CCR-1, and 50% and 55% with human CCR-2. COS cells transiently transfected with the murine homologue of human CCR-1 bind murine MIP-1 alpha and human RANTES with Kds of 3.4 nM and 4.2 nM and murine MIP-1 beta with an EC50 of 8.9 nM. The other murine beta chemokine receptor, which we have designated murine CCR-3, also binds murine MIP-1 alpha. The mRNAs for both receptors are expressed in eosinophils from IL-5 transgenic mice. The level of murine CCR-3 mRNA in these mouse eosinophils exceeds that of CCR-1 mRNA and approaches actin levels. Murine MIP-1 alpha was found to be a potent chemoattractant for murine eosinophils. Our findings suggest that the murine MIP-1 alpha ligand/receptor system is an important mediator of murine eosinophil trafficking.
Protein tyrosine phosphatase activity associates with the high affinity IgE receptor and dephosphorylates the receptor subunits, but not Lyn or Syk.
Authors: Swieter M , Berenstein E H , Siraganian R P 
Published: December 2022

Abstract
Protein tyrosine phosphorylation is an early event in the high affinity IgE receptor (Fc epsilon RI)-mediated signaling cascade leading to secretion in mast cells. Numerous proteins, including the beta- and gamma-subunits of Fc epsilon RI, become tyrosine phosphorylated after receptor aggregation. Dephosphorylation of these proteins may be important to reverse and limit transmembrane signaling. RBL-2H3 mast cell lysates were found to contain protein tyrosine phosphatase activity that dephosphorylated the tyrosine-phosphorylated beta- and gamma-subunits of Fc epsilon RI. The protein tyrosine phosphatase activity associated with Fc epsilon RI and was equally present with receptors from nonactivated and stimulated cells. Moreover, the phosphatase eluted from the immunoprecipitates and, when added back, dephosphorylated both tyrosine-phosphorylated beta- and gamma-subunits, but not tyrosine-phosphorylated Lyn or Syk. These results strongly suggest that the IgE receptor-associated protein tyrosine phosphatase may regulate the steady state level of tyrosylphosphate of the beta- and gamma-subunits and, therefore, may modulate the interaction of these subunits with other downstream molecules, such as Syk.
Rapid oscillations of actin polymerization/depolymerization in polymorphonuclear leukocytes stimulated by leukotriene B4 and platelet-activating factor.
Authors: Omann G M , Rengan R , Hoffman J F , Linderman J J 
Published: December 2022

Abstract
We previously showed that activation of polymorphonuclear leukocytes by leukotriene B4 (LTB4) and platelet-activating factor produces a rapidly oscillating actin polymerization/depolymerization response. In this study, we show that 1) oscillations are not due to the stimulated cyclic release of autocoids that could bind to cell surface receptors and activate subsequent cycles; 2) oscillations are not related to oscillations of ligand binding; and 3) the particular kinetic pattern is a property of the receptor, not of the binding constants of the ligand. The major conclusion of these studies is that the oscillations are a property of the intrinsic signaling pathways triggered by these chemoattractants. We also questioned whether increased actin nucleation activity was induced by LTB4 and found that, although LTB4 induced a transient actin nucleation response, there was not a direct correlation between oscillations of the actin polymerization/depolymerization and the actin nucleation activity. This suggests that processes other than actin nucleation, such as release of monomeric actin from monomer sequestering proteins and regulation of depolymerization, are likely to be involved.
The effect of pregnancy on polymorphonuclear leukocyte function.
Authors: Crouch S P , Crocker I P , Fletcher J 
Published: December 2022

Abstract
Pregnancy exerts suppressive effects on a number of chronic inflammatory conditions, particularly rheumatoid arthritis. We isolated peripheral blood polymorphonuclear leukocytes (PMN) from pregnant women at 30 to 34 wk (n = 34) and showed significant reductions in respiratory burst activity compared with nonpregnant controls (n = 34), as determined by lucigenin-enhanced chemiluminescence (LUCL). Responses to FMLP were reduced by 54% (p = 0.0046) and to zymosan-activated serum (ZAS) by 69% (p = 0.0043). Following LUCL responses to these agonists in women throughout the course of their pregnancy (n = 7) revealed significantly reduced responses by the second and third trimesters (p &lt; 0.005). Intracellular H2O2 production in PMN at 30 to 34 wk gestation was significantly reduced (p = 0.0454) in response to FMLP, compared with the nonpregnant controls. Investigation of adhesion molecule expression revealed no differences in CD11b or CD18. However, loss of CD62L from the PMN surface in response to FMLP and ZAS was significantly reduced at 30 to 34 wk, as compared with controls (FMLP, p = 0.049; ZAS, p = 0.01; n = 34). There were no significant differences in cell surface formyl peptide receptor expression, although there were statistical differences in LUCL responses to all concentrations of FMLP used (p &lt; 0.05). Incubating PMN with TNF, IL-8, and granulocyte-macrophage CSF increased formyl peptide receptor expression but revealed no differences between the two groups. Priming of pregnancy PMN with the same cytokines gave significantly reduced LUCL when cells were subsequently stimulated with FMLP (p &lt; 0.05; n = 6). Our results show a reduction in PMN NADPH-oxidase activity during pregnancy and may offer a partial explanation for the remission of symptoms observed in rheumatoid arthritis.
Relative perforin- and Fas-mediated lysis in T1 and T2 CD8 effector populations.
Authors: Carter L L , Dutton R W 
Published: December 2022

Abstract
IFN-gamma-secreting T1 and IL-5-secreting T2 subsets of CD8 effectors were generated in vitro using freshly isolated cells from wild-type and perforin knockout mice stimulated with allogeneic Ag-presenting cells. Both T1 and T2 effectors from wild-type mice exhibited perforin-mediated cytolysis. T1, but not T2, populations from perforin knockout mice displayed significant lysis by the Fas-mediated pathway. Th1 cells have recently been shown to be regulated by Fas and we speculate that Fas-mediated mechanisms are involved in the regulation of both Th1 and T1 populations of T cells.
Regulation of NK cell functions by TGF-beta 1.
Authors: Bellone G , Aste-Amezaga M , Trinchieri G , Rodeck U 
Published: December 2022

Abstract
The contribution of exogenous and endogenous TGF-beta 1 to human peripheral blood NK cell proliferation and activity in vitro was investigated. Exogenous bioactive TGF-beta 1 inhibited NK cell DNA synthesis and production of IFN-gamma, TNF-alpha, and granulocyte-macrophage CSF (GM-CSF) by NK cultures consisting of &gt; 98% CD56+ cells. The cytotoxic activity of NK cells was also weakly inhibited by exogenous TGF-beta 1. All TGF-beta 1-induced inhibitory effects occurred in the absence and presence of the NK cell-activating cytokines IFN-alpha, IL-2, and IL-12. Unstimulated NK cell cultures expressed steady state TGF-beta 1 mRNA detected by Northern blot analysis and produced TGF-beta protein (1.6 ng/ml), as determined by ELISA. When NK cell proliferation was induced by IL-2, IL-12, IFN-alpha, or a combination of IL-2 and IL-12, expression of TGF-beta 1 mRNA and protein was moderately and consistently reduced by approximately 20%, as compared with unstimulated control cultures. Unstimulated and rapidly proliferating NK cell cultures secreted primarily latent TGF-beta into their culture medium, as determined by the Mv1Lu bioassay. These results indicate that, in vitro, endogenous NK cell-derived TGF-beta 1 has no negative autocrine effect upon activation of NK cells by various cytokines.
IL-10 induces the tyrosine phosphorylation of tyk2 and Jak1 and the differential assembly of STAT1 alpha and STAT3 complexes in human T cells and monocytes.
Authors: Finbloom D S , Winestock K D 
Published: December 2022

Abstract
IL-10 affects monocytes and T cells by driving the progression of immune responsiveness such that Th2 lymphocyte-mediated effects predominate. In this report, we show that in monocytes and T cells IL-10 stimulates tyrosine phosphorylation of the signal transducers and activators of transcription, STAT1 alpha and STAT3, in a differential manner such that the relative formation of homo- and heterodimers varies between the two cell types. Moreover, monocytes express a novel IL-10-stimulated STAT protein with an M(r) of 70 kDa that is recognized by the anti-STAT3 Ab but is not observed in T cells. IL-10 treatment of both T cells and monocytes results in the ligand-induced tyrosine phosphorylation of tyk2 and Jak1, but not Jak2 or Jak3. Selective modulation of immune responsiveness by IL-10 in cells such as monocytes and T cells may result in part from the differential activation of STAT protein pairs.
Structure of the gene for the human myeloid IgA Fc receptor (CD89).
Authors: de Wit T P , Morton H C , Capel P J , van de Winkel J G 
Published: December 2022

Abstract
A better understanding of IgA's role in immunity requires insight in IgAR complexity. We have now isolated, characterized, and sequenced the gene encoding the prototypic human myeloid IgA FcR (CD89). The gene consists of five exons and spans approximately 12 kilobase pairs. The leader peptide is encoded by two exons, the second of which is 36 bp long and specifies the predicted peptidase cleavage site. A similar, but shorter (21 bp) mini-exon has been found in the FcR for IgG (Fc gamma R) genes, and the FcR for IgE (Fc epsilon RI alpha) gene (human and rodent). The third and fourth exons code for two homologous Ig-like domains. The final exon encodes a short extracellular region, a hydrophobic transmembrane region, and a short cytoplasmic tail. The sequence of the 5'-flanking region was determined, and one major and several minor transcription initiation sites were mapped by primer extension studies. A putative TATA box was located at an appropriate location relative to the start site. Southern blot analyses of genomic DNA confirm the restriction map generated from cloned DNA. These data define the Fc alpha R gene as a distantly related member of the IgR gene family.