bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane-proximal Ig-like domain of Fc gamma RIII (CD16) contains residues critical for ligand binding.
Authors: Hibbs M L , Tolvanen M , Carpén O
Published: December 2022

Ag-Ab complexes are cleared from the circulation through a complex system of receptors for the Fc portion of Ig (FcRs). Fc gamma RIII (CD16) is a low affinity FcR for IgG that is composed of two highly homologous Ig-like extracellular domains. Using secondary structure predictions, we located a strongly hydrophilic region in the second Ig-like domain of Fc gamma RIII that is predicted to lie between beta-strands C and C'. Substitutions of seven out of eight amino acids in this region abolished binding to IgG. Substitution of a conformationally adjacent amino acid in a bend just before beta-strand F and an amino acid in the B-C loop also affected ligand binding. However, amino acid substitutions in two different predicted loops in the second Ig-like domain as well as substitutions to three predicted loops in the first Ig-like domain had no effect on function. A chimeric Fc gamma RIII molecule lacking the second Ig-like domain was unable to bind IgG further, suggesting the presence of the binding site in the second domain. Neutralizing mAbs that inhibit Fc gamma RIII interaction with IgG were mapped to the E-F loop in the membrane proximal domain of Fc gamma RIII, providing further evidence of the importance of this region of the molecule in ligand interaction.
HLA class II antigens and the HIV envelope glycoprotein gp120 bind to the same face of CD4.
Authors: Houlgatte R , Scarmato P , el Marhomy S , Martin M , Ostankovitch M , Lafosse S , Vervisch A , Auffray C , Platier-Tonneau D
Published: December 2022

Although the HIV gp120 binding site of CD4 is well characterized, its interaction site with HLA class II molecules is still controversial. Sixty-seven mutations within the four extracellular domains of CD4 were examined for their effects on cell surface expression and conformational changes and for adhesion of HLA class II-expressing B lymphocytes and HIV gp120 binding to CD4-transfected COS cells. Mutations within the gp120 binding site affected both assays similarly, indicating that the two sites fully overlap. A few additional substitutions of residues mapping on the same face of domains 1 and 2 induced decreased rosette formation. Molecular modeling studies indicated that this is likely to be the consequence of conformational changes induced by the mutations. Thus, CD4 appears to interact with HLA class II molecules mainly through the HIV gp120 binding site and possibly through a second minor interaction site mapping on the same face of the molecule.
An isotype switched and somatically mutated rheumatoid factor clone isolated from a MRL-lpr/lpr mouse exhibits limited intraclonal affinity maturation.
Authors: Jacobson B A , Sharon J , Shan H , Shlomchik M , Weigert M G , Marshak-Rothstein A
Published: December 2022

Employing site-directed mutagenesis we have reconstructed and expressed the germ-line precursor of an expanded rheumatoid factor (RF) clone. This RF clone, designated clone F, was isolated from an autoimmune MRL/MpJ-lpr/lpr mouse. Most of the clone members were extensively mutated and isotyped-switched. The predominant isotype of clone F was gamma 3. The RF bound specifically to the MRL gamma 2 a allotype (Igh-1j) but not to the B6 gamma 2a allotype (Igh-1b). The germ-line antibody was also found to bind gamma 2a in an RF assay. The affinities of the germ-line RF and representative members of the clone were measured in an ELISA-based equilibrium binding assay. The dissociation constant (Kd) of the germ-line RF was 2.5 x 10(-6) M. All of the expressed clone members had affinities within a two- to sixfold range of the germ line, indicating that the mechanisms of somatic hypermutation and selection resulted in only limited affinity maturation of this autoantibody clone.
Fc gamma receptor cross-linking down-regulates IL-1 receptor antagonist and induces IL-1 beta in mononuclear phagocytes stimulated with endotoxin or Staphylococcus aureus.
Authors: Marsh C B , Pope H A , Wewers M D
Published: December 2022

The cross-linking of monocyte Fc gamma R is a potent stimulus for IL-1ra production but does not induce IL-1 beta. However, during systemic infection, IgG-coated bacteria can activate mononuclear phagocytes via both cell wall components and opsonized IgG. Therefore, we analyzed the effect of combinations of Fc gamma R cross-linking and bacterial cell wall components on mononuclear phagocyte IL-1 beta and IL-1ra production. Human mononuclear cells and monocytes were cultured either alone or with combinations of immobilized IgG, LPS, or heat-killed Staphylococcus aureus (HKSA). Cells cultured on immobilized IgG released large amounts of IL-1ra but no detectable IL-1 beta. In response to LPS, mononuclear cells released IL-1ra at 1000-fold lower doses of LPS than was required to induce IL-1 beta. However, when measured in the presence of immobilized IgG, the LPS sensitivity for IL-1 beta release increased 100-fold, whereas IL-1ra release correlated inversely with the LPS dose. Furthermore, HKSA, a nonendotoxin stimulus, affected mononuclear cell IL-1 beta and IL-1ra release similarly. In addition, polymyxin B, a specific endotoxin inhibitor, blocked the LPS, but not the HKSA-induced changes in IL-1 beta and IL-1ra secretion, irrespective of immobilized IgG co-stimulation. In summary, these results suggest that mononuclear phagocyte stimulation with immobilized IgG favors IL-1ra over IL-1 beta production. Conversely, the addition of LPS or HKSA to the Fc gamma R-stimulated cells augments IL-1 beta but suppresses IL-1ra production.
Epitopes on proteinase-3 recognized by antibodies from patients with Wegener's granulomatosis.
Authors: Williams R C , Staud R , Malone C C , Payabyab J , Byres L , Underwood D
Published: December 2022

The 228 amino acid primary sequence of proteinase-3 (PR3) was studied for antigenic epitopes, which react with IgG Ab in sera of patients with Wegener's granulomatosis, by synthesizing overlapping 7 mers of PR3 linear sequence on pins. Main regions of linear sequence reactivity included GHEAQPH (at residues 4-10), QPHSRPY (8-14), TQEPTQQ (65-71), ATVQLPQ (108-114), QLPQQDQ (111-117), PVPHGTQ (118-124), RVGAHDP (132-138), FCRPHNI (154-160), PRRKAGI (165-171), FGDSGGP (173-179), and IDSFVIW (189-195). All of these regions were surface accessible and seemed to be on the outside of the molecule. By substituting a glycine or an alanine for each residue within each reactive epitope, we identified the arginine at 12, valine at 119, proline at 120, histidine at 121, arginine at 132, alanine at 135, histidine at 136, and glycine at 178 as major immunodominant single residues that contribute to antigenic determinants. Visualization of these reactive regions on a three-dimensional computer-generated carbon PR3 trace diagram showed that one aspect of the molecule on the inferolateral surface comprised most of the antigenic regions. Two peptides, ATVQLPQ and RVGAHDP, when preincubated with Wegener's granulomatosis sera, produced almost complete inhibition of Wegener's granulomatosis IgG Abs either binding to PR3 on the ELISA plate or by reacting with polymorphonuclear leukocyte azurophilic granules in immunofluorescence assays for cANCA. FGDSGGP (at residues 173-179), one epitope that was recognized by Wegener's patient sera Abs, included part of the active catalytic triad for PR3. Rabbit Abs against the PR3 peptides ATVQLPQ or RVGAHDP showed a cANCA cytoplasmic granular pattern of immunofluorescence staining when they were incubated with polymorphonuclear leukocytes. These findings indicate that it is possible to identify various antigenic sites on PR3 by using overlapping 7 mers of portions of the solvent, accessible linear sequence.
Quantitative differences in cell surface expression of class I MHC antigens on murine epidermal Langerhans cells.
Authors: Sharrow S O , Barden L A , Singer A , Katz S I
Published: December 2022

Epidermal Langerhans cells are derived from cells of bone marrow origin and, as the primary APC population in the skin, are responsible for initiation of many immune responses. Consequently, cell surface expression of MHC Ags by Langerhans cells is central to their function. Although murine Langerhans cells express class II MHC Ags at high levels, their level of expression of class I MHC has been controversial. In this study, cell surface expression of multiple individual class I MHC Ags on murine epidermal Langerhans cells was analyzed using quantitative immunofluorescence. It was found that Langerhans cells differentially express products of distinct class I genes. Langerhans cells expressed low cell surface amounts of H-2K and Qa-2, whereas expression of surface H-2D and H-2L by the same cells was high. Murine epidermal Langerhans cells therefore express low cell surface amounts of some but not all class I MHC Ags. Differential surface expression of products of distinct class I MHC genes by Langerhans cells may have a profound effect on cutaneous immune responses.
Expression cloning of a human IL-12 receptor component. A new member of the cytokine receptor superfamily with strong homology to gp130.
Authors: Chua A O , Chizzonite R , Desai B B , Truitt T P , Nunes P , Minetti L J , Warrier R R , Presky D H , Levine J F , Gately M K
Published: December 2022

A cDNA encoding a human IL-12R subunit was isolated by expression cloning. This subunit is a 662 amino acid type I transmembrane protein with an extracellular domain of 516 amino acids and a cytoplasmic domain of 91 amino acids. It is a member of the hemopoietin receptor superfamily and is most closely related over its entire length to gp130 and the receptors for granulocyte-CSF (G-CSF) and leukemia-inhibitory factor. When expressed in COS cells, this IL-12R subunit binds both human and murine IL-12 with an apparent affinity of 2 to 5 nM. The transfected COS cells express both monomers and disulfide-linked dimers or oligomers of the IL-12R subunit on their surface. However, unlike the IL-6-induced dimerization of gp130, the oligomerization of the IL-12R subunit is not dependent on binding of IL-12. Only the IL-12R subunit dimers/oligomers but not the monomers bind IL-12 with an affinity of 2 to 5 nM. A polyclonal antiserum raised against this receptor subunit specifically inhibits IL-12-induced proliferation of PHA-activated PBMC. The data are consistent with the hypotheses that 1) a dimer/oligomer of the cloned IL-12R subunit (IL-12R-beta) represents the low affinity IL-12 binding site identified on human lymphoblasts, 2) the cloned receptor subunit is involved in IL-12 signal transduction, and 3) an additional, as of yet unidentified subunit is required to generate a high affinity IL-12R complex.
Upstream NFIL-6-like site located within a DNase I hypersensitivity region mediates LPS-induced transcription of the murine interleukin-1 beta gene.
Authors: Godambe S A , Chaplin D D , Takova T , Bellone C J
Published: December 2022

To define the cis-acting elements that regulate LPS-stimulated IL-1 beta gene transcription, we analyzed the murine IL-1 beta gene by digestion with DNase I. At least two hypersensitive sites were located between 2200 and 2600 bp upstream of the transcription start site in mononuclear phagocytes, but not in an IL-1 nonproducing immature T cell line. Specific DNA sequences required for LPS induction of IL-1 beta gene expression were identified within the DNase I hypersensitive (DH) region using transfection of reporter constructs that contained portions of the IL-1 beta 5'-flanking region. Two specific DNA sequences were targets for nuclear factor binding as assessed with use of electrophoretic mobility shift analysis (EMSA). One site contained a consensus sequence for NFIL-6 binding. Base substitutions within this NFIL-6 site resulted in virtual elimination of LPS-induced IL-1 beta gene transcription. Introduction of multimers of the NFIL-6-like sequence immediately 5' to homologous or heterologous promoters conferred LPS-induced transcription, indicating that this NFIL-6-like consensus site was a transcriptional activator. Anti-C/EBP beta (NFIL-6) and anti-C/EBP delta (NFIL-6 beta) Abs identified both of these proteins in complexes formed between the NFIL-6-like element and mononuclear cell nuclear extracts. C/EBP delta (NFIL-6 beta) was not detected in complexes utilizing extracts from the IL-1 nonproducing T cell line. These data are consistent with the requirement for C/EBP beta (NFIL-6) and C/EBP delta (NFIL-6 beta) in the activation of murine IL-1 beta gene expression by endotoxin.
IL-10-induced factors belonging to the p91 family of proteins bind to IFN-gamma-responsive promoter elements.
Authors: Lehmann J , Seegert D , Strehlow I , Schindler C , Lohmann-Matthes M L , Decker T
Published: December 2022

Expression of the gene encoding the high affinity IgG receptor (Fc gamma RI) is stimulated by IFN-gamma through a promoter element designated gamma-IFN activation site (GAS). This sequence binds a transcription factor designated gamma-IFN activation factor (GAF). GAF-GAS complexes contain an IFN-regulated 91-kDa protein (p91). In mouse peritoneal macrophages, IL-4 and IL-10 influenced both basal and IFN-gamma-induced expression of Fc gamma RI in opposite ways: IL-10 was stimulatory and IL-4 repressed Fc gamma RI expression. IL-4 or IL-10 did not affect the activation of GAF by IFN-gamma, but both activated the binding of latent, receptor-activated factors (RAFTs) to the Fc gamma RI GAS. RAFTs-IL-4 and -IL-10 migrated similarly in electrophoretic mobility shift assays but could be distinguished through their specificities for different GAS sequences and their reactivity with anti-p91 antisera. These experiments also revealed two distinct RAFTs-IL-10 to be members of the p91 family of proteins. The data suggest GAS-related elements to integrate signals from IFN-gamma-, IL-4- and IL-10-activated signaling paths.
Analysis of binding of monoclonal antibody to a malarial peptide by surface plasmon resonance biosensor and integrated rate equations.
Authors: Wohlhueter R M , Parekh K , Udhayakumar V , Fang S , Lal A A
Published: December 2022

Using biosensor technology and integrated rate equations, we have developed procedures to determine the kinetic parameters and equilibrium affinity constant of Ag-Ab interactions. The Ag used in these studies was a peptide that represents the major B cell epitope of the circumsporozoite protein of Plasmodium falciparum, a promising malaria vaccine candidate Ag. Measurements of association and dissociation rate constants of this peptide with the mAb 2A10 were determined by fitting integrated rate equations to binding data obtained with a BIAcore surface plasmon-resonance biosensor. We examined whether accurate estimates of initial velocity and final equilibrium levels of binding of Ab to peptides can be obtained using these methods, and whether kinetic rates and equilibrium constants obtained with systematic variation of the experimental parameters conform to a simple bimolecular model of binding. We found that initial velocity was approximately first order with respect to Ab concentration. When we used a series of four sensor cells with different peptides loads, however, we found that the initial velocity of binding appeared to be nearly independent of peptide concentration. Equilibrium analyses yielded dissociation constants of approximately 3 x 10(-7) M. Integrated rate treatment of biosensor data supports a critical examination of the assumptions on which the binding models are based and suggests a need to refine such models. Nevertheless, it provides a powerful quantitative tool for assessing the Ag-Ab binding reaction.
Origin and steady-state turnover of class II MHC-bearing dendritic cells in the epithelium of the conducting airways.
Authors: Holt P G , Haining S , Nelson D J , Sedgwick J D
Published: December 2022

Recent studies have identified a contiguous network of class II MHC-bearing dendritic cells (DC) in the airway epithelium of several species, including humans. This network seems comparable to the epidermal Langerhans cell population, comprising up to 700 DC per mm2 of airway epithelium. Moreover, it accounts for virtually all local immunostaining for class II MHC, suggesting an important role in surveillance for inhaled Ag. This study examines the turnover of these airway DC using a radiation chimera model that uses congenic rats expressing different allotypic variants of CD45, detectable via mAbs. Steady-state bone marrow renewal of the airway DC population (which is continuously depleted by migration of mature cells to draining lymph nodes) was interrupted via x-irradiation or high-dose dexamethasone, after which the resident population declined by 85% over the ensuing 72 h. After transplantation with congenic bone marrow and an initial lag period for graft establishment, the airway DC population was rapidly restored to preirradiation levels. These findings indicate a half-life of < or = 2 days for airway epithelial DC. In contrast, epidermal Langerhans cell half-life was > or = 15 days. The only comparable (short) half-life previously reported for a peripheral tissue DC population, is that derived from the gut wall. This indicates that rapidly turning over DC populations are a unique feature of the major "mucosal" organ systems, which is consistent with these DC playing an important role in surveillance of mucosal tissues for incoming Ag.
Peripheral blood mononuclear cells stimulated with C5a or lipopolysaccharide to synthesize equivalent levels of IL-1 beta mRNA show unequal IL-1 beta protein accumulation but similar polyribosome profiles.
Authors: Kaspar R L , Gehrke L
Published: December 2022

Recent reports suggest that regulation of IL-1 beta gene expression in human monocytes may include translation level as well as transcription level control mechanisms. We studied IL-1 beta expression in PBMC stimulated with recombinant complement protein C5a or with LPS. IL-1 beta mRNA was expressed by C5a-treated PBMC, but very little or no IL-1 beta protein could be detected by ELISA or by Western blot analysis using a polyclonal Ab that reacts equally with pro-IL-1 beta and processed mature IL-1 beta. LPS-treated cells produced both IL-1 beta mRNA and protein. Velocity sedimentation analysis revealed, however, that IL-1 beta mRNA assembles into large polyribosomes in both C5a- and LPS-treated cells. Translation of the IL-1 beta mRNA in C5a-treated cells is not therefore blocked at the level of protein synthesis initiation. IL-1 beta mRNA was released from polyribosomes by treating the cells with puromycin, suggesting that the ribosomes are not frozen at the elongation phase of protein synthesis. One explanation for the data is that the rate of IL-1 beta polypeptide chain elongation or termination may be diminished in the C5a-stimulated PBMC.
Discordant adaptation of human peritoneal macrophages to stimulation by lipopolysaccharide and the synthetic lipid A analogue SDZ MRL 953. Down-regulation of TNF-alpha and IL-6 is paralleled by an up-regulation of IL-1 beta and granulocyte colony-stimulating factor expression.
Authors: Knopf H P , Otto F , Engelhardt R , Freudenberg M A , Galanos C , Herrmann F , Schumann R R
Published: December 2022

Human peritoneal macrophages were exposed to increasing doses of LPS or a synthetic lipid A analogue (SDZ MRL 953) and production of the cytokines IL-1 beta, IL-6, TNF-alpha, and G-CSF was assessed at the protein and mRNA level. Cells were also prestimulated with low doses of LPS and SDZ MRL 953 to study their adaptation to a secondary challenge with high doses of LPS. The ability of macrophages to produce high levels of TNF-alpha and IL-6 after stimulation with LPS could be relieved almost completely by preincubating cells with low doses of LPS. Decreases of TNF-alpha and IL-6 production resulted from inhibition of gene transcription and/or changes in mRNA stability, as transcript levels of these cytokines were down-modulated by the process of LPS adaptation. Surprisingly, however, adapted cells were able to synthesize even larger quantities of G-CSF and IL-1 beta when exposed to a secondary LPS challenge. mRNA levels of the adapted cells remained unaltered for IL-1 beta, but were slightly increased for G-CSF as assessed by Northern blot analysis. High doses of the synthetic lipid A analogue SDZ MRL 953 were also able to adapt macrophages to a secondary LPS challenge by down-regulating TNF-alpha and IL-6 production, whereas priming secretion of G-CSF and IL-1 beta as well. We describe here the discordant adaptation of human peritoneal macrophages to a secondary LPS stimulus in vitro. These findings appear to have ramifications for the in vivo endotoxin response during inflammation and also Gram-negative septicemia.
Gender differences in IL-1 alpha, IL-1 beta, and IL-1 receptor antagonist secretion from mononuclear cells and urinary excretion.
Authors: Lynch E A , Dinarello C A , Cannon J G
Published: December 2022

Previous studies have reported increased secretion of IL-1-like activity from mononuclear cells and increased circulating levels during the luteal phase of the menstrual cycle. In this investigation, specific RIAs for the agonists IL-1 alpha and IL-beta as well as IL-1 receptor antagonist (IL-1Ra) were used to determine whether differential IL-1 secretory patterns exist between men and women or between phases of the menstrual cycle. Mononuclear cells were isolated from six men and five women at 4-h intervals from 8 am to 8 pm, with the women studied once in midfollicular phase and once in midluteal phase. In the absence of any intentional stimulation, significant differences in secretion were observed between groups (p < 0.03) for all three species of IL-1: women's cells isolated during the luteal phase secreted 5- to 10-fold more than cells from men, and women's cells isolated during the follicular phase secreted 13- to 28-fold more than cells from men. In addition, total 24-h urine samples were collected in intervals with end points coinciding with the blood samples. Urinary excretion correlated with cellular secretion for IL-beta and IL-1Ra (p = 0.024 and 0.028, respectively), indicating that the in vitro results may correspond to differential processes occurring in vivo. Although greater absolute amounts of each species of IL-1 were secreted during the follicular phase, the ratio of agonist to antagonist secreted was greater in the luteal phase (p < 0.05), in agreement with previous studies of bioactivity. These results indicate that the regulation of IL-1 secretion is fundamentally different in women compared with men and alludes to the possibility that IL-1 may serve different biologic functions in women than men.
CR2 is the primary acceptor site for C3 during alternative pathway activation of complement on human peripheral B lymphocytes.
Authors: Marquart H V , Svehag S E , Leslie R G
Published: December 2022

Human cells infected with certain viruses acquire the ability to activate the alternative pathway (AP) of complement. Complement receptor 2 on EBV-infected lymphoblastoid cell lines has been reported to act as the covalent binding site for C3b during AP activation. Using flow cytometry, we investigated the ability of normal human peripheral blood leukocytes to activate the AP in homologous serum. Deposition of C3 fragments was determined as a measurement of complement activation on each of the subpopulations of the blood cells. Incubating human peripheral blood leukocytes with homologous or autologous serum resulted in C3 deposition on B cells and, to a lesser extent, on monocytes and polymorphonuclear leukocytes. Complement activation in the presence of Mg2+ ions and EGTA revealed major involvement of the AP in the case of B cells, and to a lesser extent for other leukocyte populations examined. Preincubation of the leukocytes with polyclonal anti-complement receptor 2 Ab markedly decreased the C3 fragment deposition, as a result of in vitro AP activation, on B cells, indicating that on normal human B cells this receptor may be involved in AP activation. Freshly isolated, normal human B cells also bear low but significant amounts of C3d,g fragments on their membranes, indicating that this AP activation also occurs in vivo. AP activation was partially decreased in the presence of autologous erythrocytes (RBC) suggesting that complement regulatory proteins on RBC play a role in limiting the AP activation in vivo.
Antigen receptor-mediated transmembrane signaling in Wiskott-Aldrich syndrome.
Authors: Henriquez N V , Rijkers G T , Zegers B J
Published: December 2022

The X-linked immunodeficiency Wiskott-Aldrich syndrome (WAS) is a condition that includes a deficient anti-polysaccharide Ab response. Recently, it has been suggested that B cells from patients with WAS show a defective calcium mobilization response upon engagement of sIgM. Because primarily EBV-transformed cells were used in these studies, we tested freshly isolated blood B cells for their calcium mobilization capability upon engagement of sIg and CD19. No significant differences in the calcium mobilization capability of CD20+ B cells of four individual WAS patients compared with capability in normal controls were found. Receptor desensitization as assessed by calcium mobilization inhibition also seemed to be intact. T cells were tested for their anti-CD3-induced calcium flux and, again, no abnormalities could be observed when compared with T cells from healthy individuals. We conclude that WAS B and T cells can be stimulated into a normal calcium mobilization response when their AgRs are cross-linked. It is highly improbable that the immune dysfunction observed in WAS patients is related to a direct disorder of their B and/or T cell AgRs.
Characterization of peripheral autoregulatory mechanisms that prevent development of cyclosporin-induced syngeneic graft-versus-host disease.
Authors: Hess A D , Fischer A C , Horwitz L , Bright E C , Laulis M K
Published: December 2022

Administration of cyclosporin after syngeneic bone marrow transplantation paradoxically elicits a T lymphocyte-dependent autoaggression syndrome termed syngeneic graft-vs-host disease (SGVHD). The induction of SGVHD requires two essential components, the emergence of autoreactive lymphocytes from the thymus and the elimination of a T cell-dependent peripheral autoregulatory mechanism. These studies used the SGVHD model to further characterize this regulatory system that modifies the autoimmune potential of autoreactive effector cells. Our studies reveal that although cyclosporin did not interfere with the effector function of the autoregulatory T cells, it prevented the reconstitution of the regulatory system after syngeneic bone marrow transplantation. Furthermore, the autoregulation of SGVHD is a dynamic process specifically recognizing and responding to the autoreactive SGVHD effector cells. Challenge or priming of normal Lewis rats by intravenous infusion of irradiated SGVHD effector cells activates and amplifies this autoregulatory system resulting in: 1) a threefold enhancement of autoregulatory T cell function, 2) the appearance of a dominant autoregulatory T cell population belonging to the CD4+ T helper lymphocyte subset, and 3) the capacity of irradiated primed autoregulatory T cells to inactivate SGVHD effector lymphocytes in vitro. Additional studies reveal that effective autoregulation required a specific interaction of the TCR-alpha/beta on the autoregulatory cells with the MHC class II determinants on the autoreactive lymphocytes.
Dissociation rate of antibody-gp120 binding interactions is predictive of V3-mediated neutralization of HIV-1.
Authors: VanCott T C , Bethke F R , Polonis V R , Gorny M K , Zolla-Pazner S , Redfield R R , Birx D L
Published: December 2022

mAbs specific for the V3 loop of HIV-1 are capable of neutralizing laboratory strains of HIV-1 in vitro. In this report we use surface plasmon resonance and biosensor technology to demonstrate that the ability of V3-specific mAbs to neutralize HIV-1(MN) correlated with the dissociation rate constant of the homologous mAb-gp120 binding interaction. mAbs capable of binding diverse strains of gp120 with similar association rate constants exhibited marked differences in the dissociation rate. The dissociation rate, and not the association rate, was found to be predictive of the neutralization capacity of the mAb. Furthermore, synthetic peptides corresponding to the V3 loop of HIV-1(IIIB, MN) yielded quantitatively similar binding kinetic profiles abrogating the need for purified recombinant gp120 protein and potentially facilitating the screening of more diverse isolates. Biosensor immobilized V3 peptides were found to mimic their conformational structure in solution. This offers advantages to peptides studied by ELISA where some degree of denaturation and masking of epitopes can occur upon adsorption of peptides to plastic surfaces. The impact of amino acid substitutions within epitopes on subsequent mAb binding was dissected by observing alterations in dissociation rates. The technique provides rapid kinetic analyses of V3 Ab binding interactions with diverse V3 sequences, facilitating the efficient screening and selection of those most likely to possess the broadest and most potent HIV-1 neutralizing potentials.
Identification of epitopes of myelin oligodendrocyte glycoprotein for the induction of experimental allergic encephalomyelitis in SJL and Biozzi AB/H mice.
Authors: Amor S , Groome N , Linington C , Morris M M , Dornmair K , Gardinier M V , Matthieu J M , Baker D
Published: December 2022

A recombinant protein corresponding to the Ig-like domain of myelin oligodendrocyte glycoprotein (MOG) and synthetic 15-mer peptides of the whole MOG molecule with eight amino acid overlaps were screened for their ability to induce experimental allergic encephalomyelitis (EAE) in Biozzi AB/H (H-2dq1) and SJL (H-2S) mice. Clinical and histologic evidence of EAE developed after sensitization with the recombinant MOG protein in both AB/H and SJL mice. In AB/H mice at least three MOG epitopes within residues 1-22, 43-57, and 134-148 induced clinical and histologic EAE, whereas only the sequence 92-106 was encephalitogenic in SJL mice. Histologically, the inflammatory response in the central nervous system consisted of perivascular accumulations of CD5+ T cells and F4/80+ macrophage/microglia cells equally distributed in the brain and spinal cord. The subpial/meningeal infiltration, characteristic of mouse EAE induced with spinal cord homogenate, was only observed in cases of severe clinical disease in SJL mice in which the cellular infiltrates predominated in the spinal cord. In spite of the presence of histologic lesions in AB/H mice immunized with MOG, clinical disease either rapidly resolved or was clinically silent. In contrast to immunization of SJL mice with recombinant MOG, sensitization to MOG 92-106 induced severe clinical paralysis. After recovery these animals relapsed and exhibited demyelinated lesions. This study is the first to describe encephalitogenic epitopes of MOG that induce both clinical and histologic signs of EAE in mice. These and previous findings implicating MOG as a target Ag for Ab-mediated attack in EAE suggest that such autoreactivity to MOG may be significant in the development of human demyelinating diseases such as multiple sclerosis.
Characterization of a 70-kDa, EBV gp350/220-binding protein on HSB-2 T cells.
Authors: Hedrick J A , Lao Z , Lipps S G , Wang Y , Todd S C , Lambris J D , Tsoukas C D
Published: December 2022

EBV binds and infects HSB-2 T cells via a receptor distinct from CD21. To further study this novel EBV receptor, we expressed the first 470 amino acids of the EBV-gp350/220 using the baculovirus expression system. The recombinant gp350/220(1-470) has a m.w. of 95 kDa, reacts with anti-gp350/220 Abs, and binds CD21 in ELISA. Radiolabeled gp350/220(1-470) binds both HSB-2 and Raji cells. The gp350/220(1-470) protein also inhibits EBV binding to both HSB-2 and Raji, detected by flow cytometry. Lysates of HSB-2 cells compete with CD21 for binding to gp350/220(1-470), suggesting that the two receptors bind related epitopes on the recombinant protein. Scatchard analysis reveals that gp350/220(1-470) binds to 34,000 high affinity sites/HSB-2 cell (Kd = 0.92 x 10(-8) M) compared with the 97,000 high affinity sites bound/Raji cell (Kd = 1.78 x 10(-8) M). Utilizing a gp350/220(1-470)-affinity matrix, we identify a 70-kDa (55-kDa nonreduced) protein on the surfaces of 125I-labeled HSB-2 cells. Binding of this protein to the matrix is inhibited by anti-gp350/220 Ab 72A1. In summary, we characterize a novel EBV-binding molecule on HSB-2 cells, compare its reactivity with gp350/220 to that of CD21, and provide evidence of a gp350/220-reactive, 70-kDa protein on the surfaces of HSB-2 cells. In view of previous evidence of HSB-2 infectivity by EBV, we propose that the 70 kDa protein represents the novel EBV receptor.
Screening for cytokine messenger ribonucleic acids in purified human decidual lymphocyte populations by the reverse-transcriptase polymerase chain reaction.
Authors: Jokhi P P , King A , Sharkey A M , Smith S K , Loke Y W
Published: December 2022

At the time of human embryo implantation, large numbers of maternal CD56brightCD16- NK cells appear in the uterus. These unusual lymphocytes are believed to control the migration and differentiation of highly invasive fetally derived trophoblast cells, which infiltrate into the maternal uterus to remodel the spiral arteries during the first trimester. One possible mechanism of control is by cytokine production. In this study, highly purified (> 99%) populations of first trimester decidual CD56brightCD16- NK cells and CD3+ T lymphocytes were obtained by using a FACS. These cells were examined by reverse transcriptase PCR for their expression of mRNAs for the following cytokines: granulocyte-macrophage (GM)-CSF, CSF-1, TNF-alpha, IFN-gamma, TGF-beta 1, leukemia-inhibitory factor (LIF), and IL-2. Then, the expression was compared with that of resting PBL. The identity of the PCR products was verified by Southern blotting and hybridization with cytokine-specific probes. Both decidual CD56brightCD16- NK cells and CD3+ T cells were found to express mRNA for CSF-1, TNF-alpha, IFN-gamma TGF-beta 1, and LIF, but GM-CSF mRNA was detected only in CD56bright NK cells. IL-2 mRNA was detected in only some decidual T cell samples, and then only after at least two rounds of amplification. In contrast, peripheral blood CD56brightCD16- NK cells, CD56dimCD16+ NK cells, and CD3+ T cells expressed mRNA only for TNF-alpha and TGF-beta 1, but not for GM-CSF, CSF-1, IFN-gamma, LIF, or IL-2. These results suggest that both decidual NK cells and decidual T cells produce a variety of cytokines that may be involved in the control of trophoblast migration and differentiation during pregnancy.
Involvement of Janus kinases, p52shc, Raf-1, and MEK-1 in the IL-6-induced mitogen-activated protein kinase cascade of a growth-responsive B cell line.
Authors: Kumar G , Gupta S , Wang S , Nel A E
Published: December 2022

We have previously shown that the IL-6R in a growth-responsive B cell line, AF10, induces activation of mitogen-activated protein (MAP) kinase. Here we demonstrate the activation of Raf-1 and MEK-1, which act as a MAP kinase kinase kinase and a MAP kinase kinase, respectively, in the MAP kinase cascade induced by IL-6 in AF10 cells. IL-6 also induced tyrosine phosphorylation of the signaling transducing subunit of the IL-6R in AF10 cells, along with tyrosine phosphorylation of the gp130-associated tyrosine protein kinase JAK1 and the adaptor molecule p52shc. Although induction of tyrosine phosphorylation and activation of MAP kinase by IL-6 in a differentiation-responsive B cell line, SKW 6.4, were below the limits of detection, the phorbol ester PMA did activate Raf-1, MEK-1, and MAP kinase without inducing the phosphorylation of gp130, JAKs, or p52shc. These results suggest that JAK kinase family members associated with the IL-6R may participate in the activation of MAP kinase in AF10 cells by way of an adaptor protein and Ras-dependent kinase cascade.
Origin of a T cell clone with a mismatched combination of MHC restriction and coreceptor expression.
Authors: Suzuki H , Eshima K , Takagaki Y , Hanaoka S , Katsuki M , Yokoyama M , Hasegawa T , Yamazaki S , Shinohara N
Published: December 2022

Although the existence of a large number of CD8+ class II MHC-specific CTLs had long been noticed, the origin of such T cells with a discordant combination of specificity and phenotype has been a mystery in the positive selection model. Recent reports suggesting the independency of the positive selection of T cells from coreceptor-mediated signals raised a possibility that they might be the progeny of putative transitional, mismatched, single-positive cells appearing before positive selection as proposed in the stochastic/selective model. By developing transgenic mice carrying TCR alpha and beta chain genes of a CD8+ class II MHC Ag-specific allogeneic CTL clone QM11, the origin of such T cells with mismatched TCR specificity and coreceptor expression was studied. The results indicate that QM11 belongs to a conventional CD8+ T cell population whose maturation is dependent on a class I (or class I-like) MHC product. Consequently, the reactivity of QM11 to I-Ak can be considered to be an accidental cross-reaction.
The aggregation of the high affinity IgE receptor induces tyrosine phosphorylation of paxillin, a focal adhesion protein.
Authors: Hamawy M M , Swaim W D , Minoguchi K , de Feijter A W , Mergenhagen S E , Siraganian R P
Published: December 2022

Tyrosine phosphorylation of proteins is an essential component of high affinity IgE receptor (Fc epsilon RI) signaling and secretion. This signaling and secretion is also dependent on the organization of the cytoskeleton. Here we report that the aggregation of Fc epsilon RI on rat basophilic leukemia cells results in tyrosine phosphorylation of the cytoskeletal protein, paxillin. Tyrosine phosphorylation of paxillin is a relatively late event after Fc epsilon RI aggregation. Both the direct increase in intracellular Ca2+ with calcium ionophore and the activation of protein kinase C (PKC) with PMA induced tyrosine phosphorylation of paxillin. The optimal tyrosine phosphorylation of paxillin by Fc epsilon RI aggregation required PKC and extracellular Ca2+. However, there was also Fc epsilon RI-mediated tyrosine phosphorylation of paxillin independent of Ca2+ influx or PKC activation. By fluorescent microscopy, cell stimulation induced a redistribution of paxillin toward the periphery of the cells. Although Fc epsilon RI aggregation induced tyrosine phosphorylation of paxillin in nonadherent cells, adherence markedly enhanced this phosphorylation. Together, the data suggest a role for paxillin in Fc epsilon RI signaling.
Dominant chymotrypsin-like esterase activity in human lymphocyte granules is mediated by the serine carboxypeptidase called cathepsin A-like protective protein.
Authors: Hanna W L , Turbov J M , Jackman H L , Tan F , Froelich C J
Published: December 2022

We identified a chymotrypsin-like activity in the granules of IL-2 lymphokine-activated killer (LAK) cells and a NK cell line (YT) that reacted preferentially with the oligopeptide substrate succinyl-Phe-Leu-Phe-thiobenzyl ester (Suc-Phe-Leu-Phe-SBzl). The enzyme was isolated by detergent extraction of sedimented cytotoxic granules and then by a sequence of sieve, hydrophobic, and anion exchange chromatography. On SDS-PAGE, the protein migrated at 42 kDa in nonreduced form and became two bands (31 and 19 kDa, respectively) after reduction. Amino-terminal sequencing of the reduced protein bands revealed 100% homology with cathepsin A-like protective protein (CAPP), a lysosomal enzyme that expresses serine carboxypeptidase and deamidase activities. The carboxypeptidase activity of lymphocyte CAPP was verified by showing that the protease preferred hydrophobic amino acids in the penultimate position of the C terminus (i.e., cleaved arginine from dansyl-Phe-Leu-Arg). The presence of lymphocyte CAPP in secretory lysosomes was demonstrated by showing that Suc-Phe-Leu-Phe-SBzl activity co-migrated with tryptase and Asp-ase activities on Percoll density gradients and that 95% of the Suc-Phe-Leu-Phe-SBzl activity in granule fractions of cavitated YT cells could be immunoprecipitated with an anti-CAPP antiserum. In addition, calcium ionophore-stimulated YT cells were shown to secrete immunoprecipitable CAPP. As proposed for platelets, lymphocyte CAPP may be secreted to function extracellularly by inactivating bioactive peptides.
Signals from platelet/endothelial cell adhesion molecule enhance the adhesive activity of the very late antigen-4 integrin of human CD34+ hemopoietic progenitor cells.
Authors: Leavesley D I , Oliver J M , Swart B W , Berndt M C , Haylock D N , Simmons P J
Published: December 2022

Adhesive interactions between human CD34+ hemopoietic progenitor cells and bone marrow stromal cells control the localization, proliferation, and differentiation of CD34+ cells. Changes in adhesive interactions may contribute to the mobilization of CD34+ cells to the blood induced by chemotherapy and cytokines. Thus, the identities and functional states of adhesion receptors are critical properties of CD34+ cells. Here, we confirm that the adhesion receptors very late antigen-4 (VLA-4), LFA-1, and platelet/endothelial cell adhesion molecule-1 (PECAM-1) are expressed on the CD34+ cell line KG1a and on CD34+ normal, steady state bone marrow cells. Therapeutically mobilized CD34+ cells express similar levels of PECAM-1 but reduced levels of VLA-4 and LFA-1 in comparison with steady state bone marrow cells. Integrin adhesive activity was measured from the binding of PKH 26- or phycoerythrin-labeled CD34+ cells to FITC-labeled Chinese hamster ovary (CHO) cells expressing vascular CAM-1 (VCAM-1) or intercellular CAM-1, which are ligands for VLA-4 and LFA-1, respectively. Incubation mixtures were analyzed by flow cytometry for the loss of free CD34+ cells and gain of CD34(+)-CHO cell aggregates. VLA-4 mediates the strong and specific adhesion of KG1a cells and bone marrow CD34+ cells to VCAM-1-transfected CHO cells. CD34+ cells mobilized with granulocyte colony stimulating factor (G-CSF) or cyclophosphamide also bind VCAM-1 via VLA-4. The VLA-4-mediated adhesion of all CD34+ cells to VCAM-1 is enhanced by Abs to the coexpressed adhesion receptor PECAM-1, implicating signals transmitted from PECAM-1 as determinants of VLA-4 integrin activity. VLA-4 function in CD34+ cells mobilized with G-CSF or cyclophosphamide is equivalent to steady state CD34+ cells. LFA-1 mediates minimal adhesion between CD34+ cells and intercellular CAM-1 transfected CHO cells and is refractory to PECAM-1 modulation. We infer that VLA-4, but not LFA-1, contributes to the constitutive adhesive phenotype of CD34+ cells. PECAM-1 is probably one of several receptors that control adhesive interactions between hemopoietic progenitors and target cells by regulating the activation states of specific integrins.
Production and function of murine macrophage inflammatory protein-1 alpha in bleomycin-induced lung injury.
Authors: Smith R E , Strieter R M , Phan S H , Lukacs N W , Huffnagle G B , Wilke C A , Burdick M D , Lincoln P , Evanoff H , Kunkel S L
Published: December 2022

We investigated the role of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in bleomycin-induced lung injury, a model of interstitial lung disease. Bleomycin stimulates a T cell-dependent pulmonary inflammatory response characterized by an increase in leukocyte infiltration, fibroblast proliferation, and collagen synthesis. Intratracheal challenge of CBA/J mice with bleomycin resulted in a significant time-dependent increase in MIP-1 alpha protein levels both in whole-lung homogenates and bronchoalveolar lavage fluid. The kinetics of MIP-1 alpha expression were biphasic, with the first peak occurring at 2 days postinstillation and the second peak at 16 days. These levels of Ag expression temporally correlated with the accumulation of granulocytes, lymphocytes, and mononuclear phagocytes in the lung. In addition, immunohistochemical staining identified alveolar macrophages and bronchial epithelial cells as the primary cellular sources of MIP-1 alpha production. Interestingly, passive immunization of bleomycin-challenged mice with anti-MIP-1 alpha Abs significantly reduced pulmonary mononuclear phagocyte accumulation and fibrosis. These experiments establish that MIP-1 alpha protein is expressed in the lungs of bleomycin-treated mice and provide evidence that MIP-1 alpha promotes leukocyte accumulation and activation. Furthermore, these findings support the notion that leukocyte accumulation and activation are linked to fibrosis.
Murine inhibitory protein-kappa B alpha negatively regulates kappa B-dependent transcription in lipopolysaccharide-stimulated RAW 264.7 macrophages.
Authors: Tebo J M , Chaoqun W , Ohmori Y , Hamilton T A
Published: December 2022

The potential role of the inhibitory protein (I)-kappa B alpha gene in control of LPS-dependent transcription has been investigated in the murine macrophage cell line RAW 264.7. LPS-induced transcription in macrophages is believed to involve activation of members of the Rel homology family of transcription factors, and may be negatively regulated by cytoplasmic inhibitor proteins collectively termed I-kappa Bs. To evaluate the role of I-kappa Bs in LPS-stimulated macrophages, murine I-kappa B alpha (ml-kappa B alpha) has been expressed as a glutathione-S-transferase (GST) fusion protein and examined for its ability to control kappa B binding activities in nuclear extracts from LPS-treated RAW 264.7 macrophages. ml-kappa B alpha-GST inhibited LPS-induced kappa B binding activity from RAW 264.7 cells in a phosphorylation-dependent fashion, but did not affect IFN-alpha-induced IFN stimulus response element binding. Recombinant I-kappa B alpha inhibited kappa B motif binding by nuclear factor-kappa B1, RelA, and c-Rel as indicated by studies using UV radiation-induced covalent cross-linking to a bromodeoxyuridine-substituted kappa B oligonucleotide. Transfection of macrophages with an expression vector encoding ml-kappa B alpha inhibited LPS-stimulated transcription driven by a 243-bp promoter sequence obtained from the 5' flanking region of the murine IP-10 gene. This promoter sequence contains two kappa B motifs that have been shown to be critical to LPS-dependent reporter gene transcription. The kappa B sites seem to be the specific target of I-kappa B alpha function, as reporter gene transcription driven by these motifs in the context of a heterologous thymidine-kinase promoter (TK) also was inhibited by co-transfection with ml-kappa B alpha. These observations indicate that ml-kappa B alpha is capable of controlling kappa B-dependent transcription in LPS-stimulated murine macrophages.