bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical role of Lyn kinase in inhibition of neutrophil apoptosis by granulocyte-macrophage colony-stimulating factor.
Authors: Wei S , Liu J H , Epling-Burnette P K , Gamero A M , Ussery D , Pearson E W , Elkabani M E , Diaz J I , Djeu J Y
Published: December 2022

The signal pathway for control of apoptosis in human neutrophils is currently unknown. In this study, we provide the first evidence that a Src family tyrosine kinase, Lyn, plays a key role in inhibition polymorphonuclear (PMN) cell death. Several nuclear proteins associated with apoptosis, i.e., p53, cdc2, and Rb, were absent from PMN. Bcl-2, known to inhibit apoptosis, was also not expressed. Programmed cell death that rapidly occurred in PMN could be arrested by granulocyte-macrophage CSF (GM-CSF), but this activation did not induce p53, cdc2, retinoblastoma, or Bcl-2 expression. Instead, GM-CSF produced a rapid activation of Lyn and Hck, but not Fgr, tyrosine phosphorylation within 1 min. Co-immunoprecipitation studies indicated that only Lyn, but not Hck, was physically coupled to GM-CSF receptor. By histologic assessment and evaluation of DNA fragmentation, only antisense Lyn, but not antisense Hck or antisense Fgr, could reverse the cell survival advantage provided by GM-CSF. Therefore, the physical coupling of Lyn to GM-CSF receptor and its early activation are required for inhibition or delay of apoptosis in PMN.
Thymic expression of myelin basic protein (MBP). Activation of MBP-specific T cells by thymic cells in the absence of exogenous MBP.
Authors: Fritz R B , Zhao M L
Published: December 2022

Previous studies have shown golli-myelin basic protein (MBP) mRNA to be expressed in the thymus of normal SJL mice, but translation of the mRNA was not assessed. To test for the presence of immunoreactive protein, single cell suspensions were prepared from adult SJL thymus and cultured with syngeneic MBP-specific T cells. After 48 h [3H]thymidine was added to the microcultures to assess T cell proliferation. MBP-specific T cell lines proliferated strongly (stimulation index range, 13-31). T cell lines specific for MBP exon 2, MBP peptide 89-101, proteolipid protein peptide 139-151, and OVA gave stimulation indices of 10-13, 5-6, 2-3, and 2-3, respectively. Stimulatory activity could be abrogated by irradiation of either the thymic cells or the MBP-specific T cells. Stimulatory activity was a property of a minor population of plastic-adherent thymic cells. Monoclonal anti-I-As Ab added to the microcultures inhibited the reaction by 77%. MBP-specific T cells cultured with syngeneic nonirradiated thymus cells in the absence of added MBP transferred experimental autoimmune encephalomyelitis adoptively to syngeneic recipients. These findings indicate that golli-MBP mRNA is translated in normal SJL thymus, and that peptides reactive with MBP-specific T cells in the context of class II MHC molecules are expressed.
Induction of anergy in CD8 T cells by B cell presentation of antigen.
Authors: Höllsberg P , Batra V , Dressel A , Hafler D A
Published: December 2022

Induction of T cell anergy is thought to occur during activation in the absence of adequate costimulation. Here we demonstrate induction of anergy in a CD8 T cell clone by its cognate Ag in the presence of B7-1 and B7-2 costimulation. Primary activation of a CD28+CD8+ T cell clone by either human T cell lymphotrophic virus type I (HTLV-I) Tax11-19 peptide-pulsed EBV-transformed B cells, CD40L-stimulated B cells, or T cells was sufficient to induce complete unresponsiveness to a secondary Ag challenge. This was not caused by lack of B7 costimulation since the APCs expressed B7-1 and B7-2 and failed to induce anergy in an MBP peptide 84-102-reactive CD4 T cell clone. While anergic CD8 T cells did not proliferate, they retained their ability to lyse peptide-pulsed target cells. However, Ag stimulation failed to induce IL-2 mRNA transcription and IL-2 secretion, although immediate early tyrosine phosphorylation was normal and anti-CD3 cross-linking induced identical levels of CD40L expression in anergized and non-anergized CD8 T cells. Secondary Ag stimulation in the presence of exogenous IL-2, however, resulted in normal proliferative response. Moreover, while stimulation of CD8 T cells with PHA and B cells induced anergy, CD8 T cell stimulation with PHA and mononuclear cells failed to do so. In addition, the presence of mononuclear cells during the exposure of CD8 T cells to peptide-pulsed B cells prevented the induction of anergy. Together, our observations demonstrate that at least a subpopulation of CD8 T cells are anergized when costimulation is provided by B cells or T cells.
Preferential involvement of Go and Gz proteins in mediating rat natural killer cell lysis of allogeneic and tumor target cells.
Authors: Maghazachi A A , Al-Aoukaty A , Naper C , Torgersen K M , Rolstad B
Published: December 2022

IL-2-activated NK cells from PVG rats potently lyse target cells expressing allo-MHC class I determinants. Here, we investigated the role that G proteins play in mediating this activity. Pretreatment of NK cells with pertussis toxin (PT) or cholera toxin (CT) inhibited NK cell killing of tumor (YAC-1 or P815), and allogeneic target cells. ADP ribosylation assay revealed that PT ADP ribosylates a 39-kDa G protein, whereas CT ADP ribosylates a 45 to 47-kDa G protein in PVG NK cell membranes. Membranes prepared from intoxicated NK cells with either PT or CT lost their ability to incorporate [32P]NAD. These membranes possess Gi, Go, Gs, and Gz as demonstrated by immunoblot analysis. However, Gq was not clearly detected by this method. IL-2-activated NK cells were permeabilized with streptolysin O. Permeabilized cells incorporated Abs to Gi, Go, Gz, Gs, and Gq as determined by flow cytometric analysis. When Abs to Go or Gz, but not to Gi, Gs, or Gq, were incorporated inside permeabilized NK cells, a significant reduction in the lysis of tumor or allo-MHC target cells was observed, suggesting that Go and Gz play important roles in transducing the signals necessary to lyse target cells. Our results show for the first time a role for G proteins in mediating NK cell killing of allo-MHC-encoded target cells, and provide evidence for Gz protein involvement in NK cell recognition of target cells. The effect of Gz is novel and has not been previously described in any other system or cell type.
Biochemical and serologic evidence for the existence of functionally distinct forms of the CD94 NK cell receptor.
Authors: Pérez-Villar J J , Carretero M , Navarro F , Melero I , Rodríguez A , Bottino C , Moretta A , López-Botet M
Published: December 2022

The CD94 NK cell receptor is assembled as a disulfide-linked dimer and appears to be encoded by a single-copy gene of the C-type lectin superfamily. In reverse Ab-dependent cellular cytotoxicity assays, CD94-specific mAbs may either trigger or inhibit cytotoxicity in distinct subsets of NK clones, termed groups A and B, respectively. The molecular basis for this functional ambivalence of CD94 has been addressed. CD94 molecules immunoprecipitated with the HP-3B1 mAb from the two different subsets of NK clones were comparatively analyzed by SDS-PAGE. Under reducing conditions, the stimulating form of CD94 from group A clones displayed a significantly lower Mr (39 kDa) than the inhibitory form of group B clones (Mr = 43 kDa). Analyses of N-glycanase and V8 protease-digested samples indicated that the two CD94 forms are homologous. A CD94-specific mAb (Z199) that did not recognize cells transfected with a CD94 cDNA (LL288) was characterized. Z199 did not bind to group A clones, whereas its reactivity with group B NK cells was indistinguishable from that of other CD94-specific mAbs. Different from the HP-3B1 mAb, the Z199 mAb displayed only inhibitory effects in reverse Ab-dependent cellular cytotoxicity assays. Immunoprecipitation studies confirmed that Z199 selectively identified the 43-kDa CD94. Our study proves the existence of at least two biochemically and serologically distinct CD94 molecules, whose selective/predominant expression at the clonal level correlates with the pattern of response (i.e., inhibition vs activation) of NK cells to ligation by CD94-specific mAbs.
Rapid immune activation by CpG motifs in bacterial DNA. Systemic induction of IL-6 transcription through an antioxidant-sensitive pathway.
Authors: Yi A K , Klinman D M , Martin T L , Matson S , Krieg A M
Published: December 2022

Unmethylated CpG dinucleotides (CpG motif) in bacterial DNA or synthetic oligodeoxynucleotides (CpG DNA) rapidly activate murine B cells to secrete IL-6 and IgM, as well as to proliferate. Within 30 min after CpG DNA stimulation in vivo, IL-6 mRNA levels were increased in liver, spleen, and thymus cells. Serum IL-6 protein was markedly increased within 1 h of stimulation. Treatment of a B cell line with CpG DNA led to an increase in the transcriptional activity of the IL-6 promoter. This CpG DNA-induced IL-6 production was not mediated via either a protein kinase C (PKC)-, protein kinase A (PKA)-, or nitric oxide (NO.)-dependent pathway but was inhibited by an antioxidant. In addition, the level of intracellular reactive oxygen species was increased within 20 min after CpG DNA, but not control non-CpG DNA, treatment. These results suggest that CpG DNA-induced IL-6 production is mediated through a reactive oxygen intermediate-dependent pathway. CpG DNA-mediated IL-6 production was enhanced by simultaneous signals delivered through the Ag receptor. The addition of neutralizing Abs against IL-6 to B cell cultures along with CpG oligodeoxynucleotides essentially abolished the CpG DNA-induced increased IgM secretion but had no significant effect on the B cell proliferation induced by the CpG motif. Our results suggest that the induction of IL-6 expression in response to CpG motifs in bacterial DNA may be an important immune defense mechanism that facilitates a rapid response to microbial infection.
Identification of the rhesus monkey HLA-G ortholog. Mamu-G is a pseudogene.
Authors: Boyson J E , Iwanaga K K , Golos T G , Watkins D I
Published: December 2022

HLA-G is a nonclassical MHC class I molecule that is primarily expressed in the placenta. To investigate whether rhesus monkeys possess an HLA-G ortholog, we cloned and sequenced MHC class I cDNAs from the rhesus placenta. We identified two rhesus MHC class I cDNAs with sequence similarity to HLA-G. Each cDNA contained premature stop codons and frameshift mutations, suggesting that it was derived from an MHC class I pseudogene. Gene trees constructed using MHC class I alleles from human and nonhuman primates revealed that the rhesus placental pseudogene alleles clustered with HLA-G orthologs from the human, chimpanzee, and gorilla. These data suggested that this rhesus MHC class I pseudogene is an HLA-G ortholog. This locus was, therefore, designated Mamu (Macaca mulatta)-G. PCR amplification of a portion of Mamu-G from the genomic DNA of five rhesus monkeys resulted in the identification of five additional Mamu-G alleles and revealed the presence of four Mamu-G alleles in one rhesus monkey, suggesting that Mamu-G had been duplicated in this individual. Furthermore, the analysis of 81 MHC class I clones isolated from a rhesus placenta cDNA library did not result in the isolation of Mamu-G cDNAs, nor the isolation of any additional HLA-G homologs, suggesting that Mamu-G was transcribed at negligible levels. Given the similarity of rhesus monkey and human placenta structure and function, these data raise interesting questions regarding the role of HLA-G in pregnancy.
CD97 is a processed, seven-transmembrane, heterodimeric receptor associated with inflammation.
Authors: Gray J X , Haino M , Roth M J , Maguire J E , Jensen P N , Yarme A , Stetler-Stevenson M A , Siebenlist U , Kelly K
Published: December 2022

CD97 is a receptor that spans the membrane seven times, a defining feature of G protein-coupled receptors. CD97 is predominantly expressed in leukocytes, but the function and accurate protein structure of this receptor have not been described. We show here that CD97 has the novel property among G protein-coupled receptors characterized to date of being processed intracellularly in either the endoplasmic reticulum or early Golgi from a proprotein into a noncovalently associated two-subunit structure that becomes expressed on the cell surface and is composed of a large extracellular protein (CD97alpha) and a seven-membrane spanning protein (CD97beta). CD97beta is part of an evolutionarily conserved subfamily of four proteins, including two Caenorhabditis elegans proteins of as yet unknown function, which is distinct from but most closely related to the glucagon receptor family. CD97alpha exists in three alternatively spliced isoforms that contain between three and five epidermal growth factor (EGF)-like repeats that are related to the calcium binding EGF-like repeats in the microfibril protein fibrillin. Leukocytes strongly positive for CD97 are concentrated at sites of inflammation relative to CD97 expression in normal lymphoid tissues. Soluble CD97alpha was found in body fluids from inflamed tissues, suggesting that a functional consequence of the CD97 heterodimeric structure is the stable existence of CD97alpha in a cellfree form. CD97 appears to be a multifunctional protein that may play a signal transduction role associated with the establishment or development of an inflammatory process.
Non-small cell lung cancer-derived soluble mediators and prostaglandin E2 enhance peripheral blood lymphocyte IL-10 transcription and protein production.
Authors: Huang M , Sharma S , Mao J T , Dubinett S M
Published: December 2022

Studies suggest that IL-10 may contribute to tumor-associated immunosuppression. In the current study we evaluated the capacity of human non-small cell lung cancer (NSCLC) cell lines to induce PBL IL-10 production. We observed a 10- to 100-fold increase in human PBL IL-10 production following exposure to NSCLC cell supernatants. The tumor-induced increase in PBL IL-10 production was partially blocked by pretreatment of the tumors with the PG inhibitor indomethacin. NSCLC lines were found to constitutively produce PGE2. Exogenous PGE2 also induced PBL IL-10 production in a dose- and time-dependent manner. Both PGE2 and NSCLC supernatant-induced PBL IL-10 production were due to an increase in the IL-10 mRNA transcriptional rate. To evaluate the significance of tumor-induced lymphocyte IL-10 production, the capacity of PBL to produce IFN-gamma during culture in tumor supernatants was assessed in the presence of specific anti-IL-10 mAb. We found enhanced PBL IFN-gamma production following anti-IL-10 treatment. These in vitro studies imply that NSCLC-induced PBL IL-10 production may serve to shift the Th1/Th2 cytokine axis at the tumor site and thus inhibit cell-mediated anti-tumor immune responses. These findings identify a mechanism by which lung cancer cells may escape host immune surveillance. We conclude that NSCLC-derived soluble mediators, including PGs, may play an immunoregulatory role through induction of lymphocyte IL-10 production.
Dietary n-3 fatty acids increase spleen size and postendotoxin circulating TNF in mice; role of macrophages, macrophage precursors, and colony-stimulating factor-1.
Authors: Blok W L , de Bruijn M F , Leenen P J , Eling W M , van Rooijen N , Stanley E R , Buurman W A , van der Meer J W
Published: December 2022

In experimental studies in mice, dietary supplementation with n-3 fatty acids (FA) alleviates inflammation and increases resistance to infection. Nevertheless, TNF production capacity was found to be increased in n-3 FA-fed mice. We previously found increased relative spleen weights in n-3 FA-fed mice. In this study, the nature of this increased spleen size was further investigated. Spleen cellularity was increased significantly in mice fed n-3 FA (fish oil 15% w/w), compared with controls fed corn oil (15%) or normal lab chow (p < 0.05). Experiments with T cell-deficient nude mice and experiments using macrophage depletion through liposomal dichloromethylene-biphosphonate revealed that the increase in spleen cellularity is T cell independent and largely due to macrophage accumulation in the spleen. Accumulation of marginal zone and red pulp macrophages was histologically and immunohistochemically confirmed. n-3 FA induced peripheral blood monocytosis and an aspecific increase in bone marrow cellularity. Postendotoxin circulating TNF concentrations were increased significantly in n-3 FA-fed mice compared with controls. Splenectomy did not abolish this increase in circulating TNF. However, after macrophage depletion through liposomal dichloromethylene-biphosphonate, circulating TNF was not detectable after endotoxin challenge. Circulating concentrations of CSF-1 did not differ between the various experimental groups. It is suggested that the cellular changes observed relate to increased constitutive production of TNF.
Basophil priming by neurotrophic factors. Activation through the trk receptor.
Authors: Bürgi B , Otten U H , Ochensberger B , Rihs S , Heese K , Ehrhard P B , Ibanez C F , Dahinden C A
Published: December 2022

There is increasing evidence that nerve growth factor (NGF) acts on cells of the immune system, apart from its neurotrophic effects. In human basophils, NGF potentiates mediator release and primes the cells to produce leukotriene C4 in response to C5a. It is, however, unknown whether other homologous neurotrophins also act outside the nervous system, and whether activation of basophils by NGF requires interaction with trk tyrosine kinase receptors, the low affinity NGF receptor (LNGFR), or both. A triple mutant NGF designed to interrupt binding to the LNGFR was found to activate basophils with equal efficacy as wild-type NGF, demonstrating that the LNGFR is not necessary. Despite a 10 times lower potency of mutant NGF, no LNGFR expression was detected by FACS analysis. Brain-derived neurotrophic factor, which interacts with trkB, was inactive at concentrations up to 1000 ng/ml (> 30,000-fold lower potency than NGF), while neurotrophin-3, which is thought to interact with trkC, trkB, and more weakly with trk, induced a threshold effect at 300 ng/ml (approximately 10,000-fold lower potency), demonstrating that 1) the LNGFR cannot deliver a direct signal; and 2) basophils do not express functional trkB and trkC receptors. In agreement with the functional data, basophils (in contrast to other granulocyte types) expressed mRNA for trk, but not trkB or trkC, and no or minimal mRNA for LNGFR. These data demonstrate that human blood basophils express functional trk receptors that do not require the participation of LNGFR, and that, among the neurotrophin family, NGF is unique in priming basophils.
Potential role of membrane internalization and vesicle fusion in adhesion of neutrophils in response to lipopolysaccharide and TNF.
Authors: Detmers P A , Thieblemont N , Vasselon T , Pironkova R , Miller D S , Wright S D
Published: December 2022

Human polymorphonuclear leukocytes (PMN) respond to LPS with strongly increased integrin-mediated adhesion. While the first step of this process has been identified as the interaction of LPS with CD14 on the cell surface, subsequent steps remain to be elucidated. The experiments presented here suggest that monomeric LPS is internalized in vesicles, and uptake may be required for signaling. Fluorescently labeled LPS presented as monomeric complexes with soluble CD14 appeared in the plasma membrane of PMN by 5 min and was concentrated in cytoplasmic vesicles by 20 min. Adhesion in response to LPS/soluble CD14 occurred only after a 15- to 20-min lag period, consistent with endocytosis occurring before signal generation. In contrast, there was no time lag for adhesion in response to the formyl peptide formyl-norleucyl-leucyl-phenylalanine (fNLLP). Adhesion in response to LPS, but not fNLLP, was completely blocked by lowering the temperature to 19 degrees C, a procedure that prevents vesicle fusion. These studies indicated that an event with the time and temperature dependence of endocytosis precedes signaling by LPS. Cytochalasin D, an inhibitor of phagocytosis, and wortmannin, an inhibitor of phosphatidylinositol 3-kinase that blocks vesicle fusion and phagocytosis, both completely blocked adhesion in response to LPS but not in response to fNLLP. These results support the idea that LPS internalization and early endosomal fusion may be required for signal transduction. Parallel studies showed that the adhesion response to TNF had time, temperature, and inhibitor sensitivities nearly identical with those of LPS, suggesting that responses to TNF may also include an obligate vesicle fusion step.
Induction of the CD11b gene during activation of the monocytic cell line U937 requires a novel nuclear factor MS-2.
Authors: Farokhzad O C , Shelley C S , Arnaout M A
Published: December 2022

The differentiation of myeloid precursors into mature myelomonocytic cells is characterized by the induction of the gene encoding the beta2 integrin CD11b. The transcription factors Sp1 and PU.1 prime the CD11b promoter, but the nature of the factors responsible for its inducible expression are unknown. In addition to the CD11b gene, the homologous genes encoding CD11a and CD11c also exhibit inducible expression during myeloid differentiation. Therefore, we compared the nucleotide sequences of the CD11a, CD11b, and CD11c gene promoters to identify common elements that might contribute to inducible expression. This analysis identified one such element repeated four times within the CD11b promoter. Mutation of these elements indicated that two, MS-2beta and MS-2gamma, are critical to the induction of the CD11b gene during differentiation of the pro-monocytic cell line U937. Electrophoretic mobility shift assays indicate that MS-2beta and MS-2gamma interact with nuclear factors that are induced during U937 differentiation. These factors are detected at the time the CD11b promoter is activated. The molecular mass of these factors is approximately 28 kDa, and their DNA binding characteristics are indistinguishable from those of the novel nuclear factor MS-2. Taken together, our data indicate that MS-2 mediates induction of the CD11b gene as cells of the monocytic lineage mature. The presence of multiple potential binding sites for MS-2 in the promoter regions of a wide range of genes expressed in mature myeloid cells suggests this factor plays a general role in myeloid differentiation.
Induction of the P2z/P2X7 nucleotide receptor and associated phospholipase D activity by lipopolysaccharide and IFN-gamma in the human THP-1 monocytic cell line.
Authors: Humphreys B D , Dubyak G R
Published: December 2022

The activation of phospholipase D (PLD) was used as a marker for P2z nucleotide receptor (P2zR) activity in the human THP-1 monocytic cell line. While untreated THP-1 cells displayed little PLD response to the P2zR agonist 3'-O-(4-benzoyl)benzoyl (Bz)ATP, treatment with either IFN-gamma or bacterial LPS induced a BzATP-mediated stimulation of PLD activity. Treatment of cells with combinations of IFN-gamma and LPS resulted in synergistic induction. P2z receptors mediated these effects because: 1) reduction of extracellular divalent cation concentration increased agonist potency; 2) only BzATP or ATP acted as agonist nucleotides; 3) oxidized ATP, an inhibitor of the P2z receptor, abolished the response. The P2zR-stimulated PLD was rapidly activated (t(1/2) = 1.5 min), completely inhibited by KN-62, a calcium-calmodulin kinase II inhibitor, and only partially repressed by bisindolylmaleimide, a protein kinase C inhibitor. The P2zR-mediated PLD activity was distinguished from phorbol ester-stimulated PLD activity because the latter was slowly activated (t(1/2) > 15 min), unaffected by oxidized ATP or KN-62, and completely inhibited by bisindolylmaleimide. IFN-gamma and LPS treatment also synergistically induced P2zR-dependent changes in membrane permeability and cytolysis, as indicated by BzATP-mediated Ca2+ influx, ethidium bromide uptake, and lactate dehydrogenase release. Finally, IFN-gamma and LPS synergistically up-regulated mRNA encoding the P2X7 receptor, a recently cloned ATP-gated channel that exhibits a P2zR phenotype.
Sequential acquisition of mitochondrial and plasma membrane alterations during early lymphocyte apoptosis.
Authors: Castedo M , Hirsch T , Susin S A , Zamzami N , Marchetti P , Macho A , Kroemer G
Published: December 2022

When cells undergo nuclear apoptosis (chromatin condensation, DNA fragmentation), they already manifest at least three alterations that can be quantified cytofluorometrically at the single-cell level: 1) a loss of mitochondrial transmembrane potential (delta psi m), 2) an increased production of superoxide anions, and 3) the aberrant exposure of phosphatidylserine (PS) residues on the outer plasma membrane leaflet. This latter alteration allows for the phagocytic recognition/elimination of apoptotic cells. In this work, we show that cells first undergo the delta psi m disruption and that PS exposure only affects cells that already have a low delta psi m. Pharmacologic modulation of apoptosis with inhibitors of macromolecule synthesis or proteases, as well as with drugs stabilizing the delta psi m, indicates that delta psi m disruption and PS exposure are coregulated. Interventions on apoptosis-regulatory genes (p53, bcl-2) confirm the coregulation of delta-psi-m disruption, PS exposure, and nuclear signs of apoptosis. In all conditions in which apoptosis is prevented, the delta psi m remains stable and PS cannot be detected on the cell surface. Reactive oxygen species do not contribute to PS exposure, based on two lines of evidence. First, among thymocytes undergoing apoptosis in response to dexamethasone, delta psi mlow cells first expose PS and then hyperproduce superoxide anion. Second, exogenous sources of reactive oxygen species or the superoxide anion-generating drug menadione fail to cause rapid PS exposure. Instead, direct interventions on mitochondria using inhibitors of the respiratory chain or the F1 ATP synthase cause PS exposure in cells subsequent to delta psi m disruption. This effect is also obtained in anucleate cells, indicating that the nucleus does not intervene in the sequence of events coupling mitochondrial dysfunction to PS exposure. Altogether, these data underline the functional impact of mitochondrial alterations on the apoptotic process.
Type I (CD64) and type II (CD32) Fc gamma receptor-mediated phagocytosis by human blood dendritic cells.
Authors: Fanger N A , Wardwell K , Shen L , Tedder T F , Guyre P M
Published: December 2022

Three classes of Fc receptors for IgG, Fc gamma RI (CD64), Fc gamma RII (CD32), and Fc gamma RIII (CD16), are expressed on blood leukocytes. Although Fc gamma R are important phagocytic receptors on phagocytes, most reports suggest that dendritic cells lack Fc gamma R-mediated phagocytosis and express significant levels of only CD32. We now report that phagocytically active forms of both CD64 and CD32 are expressed significantly on at least one subset of human blood dendritic cells. Countercurrent elutriation and magnetic bead selection were used to rapidly enrich subsets of blood dendritic cells (CD33brightCD14-HLA-DRbrightCD83-) and monocytes (CD33brightCD14brightHLA-DRdimCD83-). Upon culture for 2 days, dendritic cells became CD83-positive and markedly increased HLA-DR expression, whereas monocytes did not express CD83 and exhibited reduced levels of HLA-DR. Constitutive CD64 expression was identified on this circulating dendritic cell population, but at a lower level than on monocytes. CD64 expression by dendritic cells and monocytes did not decrease during 2 days in culture, and was up-regulated on both cell types following incubation with IFN-gamma. Freshly isolated blood dendritic cells performed CD64- and CD32-mediated phagocytosis, although at a lower level than monocytes. Dendritic cells generated by culture of adherent mononuclear cells in granulocyte-macrophage CSF and IL-4 also up-regulated CD64 following IFN-gamma stimulation, and mediated CD64-dependent phagocytosis. These results indicate that both CD64 and CD32 expressed on blood dendritic cells may play a role in uptake of foreign particles and macromolecules through a phagocytic mechanism before trafficking to T cell-reactive areas.
Regulation of the B cell response to T-dependent antigens by classical pathway complement.
Authors: Fischer M B , Ma M , Goerg S , Zhou X , Xia J , Finco O , Han S , Kelsoe G , Howard R G , Rothstein T L , Kremmer E , Rosen F S , Carroll M C
Published: December 2022

Mice deficient in complement components C3 (C3 -/-) and C4 (C4 -/-) were found to have a profound defect in their Ab response to a T-dependent Ag (bacteriophage (phi X174). Characterization of the deficient mice demonstrated a diminished level of peanut agglutinin+ germinal centers and a failure in isotype switching despite normal B cell signaling in vitro. The nature of the defect was found to lie at the B cell level, as the T cells were primed in C3- and C4-deficient mice as well as those in wild-type mice. These results, and the finding that the defect could be partly reversed by a 10-fold increase in Ag dose, support the hypothesis that covalent attachment of complement ligands, i.e., C3b and C3d to the Ag-Ab complex, increases its immunogenicity.
Gamma delta TCR+ hybridomas derived from mice preimmunized via the portal vein adoptively transfer increased skin allograft survival in vivo.
Authors: Gorczynski R M , Cohen Z , Leung Y , Chen Z
Published: December 2022

C57BL/6 mice receiving pretransplant immunization with C3H.SW spleen cells via the portal vein, but not the vena cava, show Ag-specific delayed rejection of allogeneic C3H.SW skin grafts. This delayed rejection is not seen if preimmunization is performed in gamma delta TCR knockout (C57BL/6-Tcrdtm1Mom) mice. gamma delta TCR+ and alpha beta TCR+ hybridoma cells were prepared from Peyer's patch cells harvested from C57BL/6 mice 4 days following portal venous immunization with 100 x 10(6) irradiated C3H.SW spleen cells and skin grafting with C3H.SW tail skin. After recloning, these hybridoma cells were tested for cytokine production in vitro following restimulation with irradiated C3H.SW spleen cells and for their ability to delay rejection of C3H.SW skin grafts after adoptive transfer to C57BL/6 mice. Delayed graft rejection was a function of cells that showed preferential production of IL-10, not IFN-gamma, in vitro, independent of the source (vena cava or portal vein immunized mice) or the TCR phenotype of the hybridoma. Simultaneous infusion of anti-IL-10 mAb abolished this graft prolongation effect of transferred gamma delta TCR+ hybridomas. Hybridoma cells producing IL-10 on restimulation could polarize cytokine production from freshly stimulated mesenteric lymph node away from production of IL-2 and IFN-gamma, and toward IL-4, IL-10, and TGF-beta production. This immunoregulation by hybridoma cells in vivo and in vitro was observed even for third party Ag-stimulated mice/cells as long as the hybridoma cells themselves received stimulation with their specific Ag.
Chemical denaturation and modification of ovalbumin alters its dependence on ubiquitin conjugation for class I antigen presentation.
Authors: Michalek M T , Grant E P , Rock K L
Published: December 2022

Class I presentation of microinjected native OVA by a temperature-sensitive ubiquitin conjugation mutant, ts85, but not wild-type murine cells, was markedly inhibited following incubation at a nonpermissive temperature. In contrast, the nonpermissive temperature did not affect class I presentation of a minimal OVA peptide expressed in the cytosol. Therefore, these results provide a second example in which a temperature sensitive mutation in the ubiquitin conjugation pathway inhibits MHC class I presentation of native OVA. Surprisingly, incubation at the nonpermissive temperature did not inhibit class I presentation of chemically denatured and alkylated OVA microinjected into the cytosol of mutant cells. Similarly, the presentation of endogenously synthesized OVA (which is expressed from a recombinant vaccinia virus and, presumably, is misfolded in the cytosol) was also not inhibited in both mutant cell lines. Methylation of the lysine groups in denatured OVA, which blocks ubiquitin conjugation, reduced but did not eliminate the presentation of denatured OVA, providing evidence for both ubiquitin-dependent and ubiquitin-independent pathways for class I presentation. In contrast, a proteasome inhibitor blocked class I presentation of all forms of OVA, while a control peptide aldehyde was not inhibitory. These results indicate that modification of the structure of a protein can influence its requirements for ubiquitin conjugation for efficient class I presentation, with the key alteration possibly being the loss of proper conformation. However, regardless of the form of the Ag, the proteasome appears to be required for generating peptides from both endogenously synthesized and microinjected OVA for class I presentation.
TCR triggering of anergic CD4 T cells in murine AIDS induces apoptosis rather than cytokine synthesis and proliferation.
Authors: Muralidhar G , Koch S , Broome H E , Swain S L
Published: December 2022

Murine AIDS (MAIDS) induced by infection of C57BL/6 mice with a mixture of retroviruses known as LP-BM5 is characterized by lymphadenopathy, splenomegaly, and T and B cell dysfunction. By labeling with bromodeoxyuridine in vivo, we found vigorous CD4 T cell proliferation during the initial stages of infection, yet a loss in their ability to function both in vivo and in vitro. In addition, a significant fraction of the CD4 T cell population in infected mice undergoes spontaneous apoptosis in vivo. Upon in vitro stimulation with anti-CD3 plus PMA, anergic CD4 T cells from mice with MAIDS fail to progress through the cell cycle (G0/G1 arrest), and a fraction of the cells undergoes apoptosis. The addition of IL-2 along with TCR-mediated stimulation not only fails to rescue CD4 T cells from apoptosis, but enhances activation-induced cell death. To further understand the regulation of the suicide pathway(s) of anergic CD4 T cells vs the cytokine synthesis pathway(s) of normal CD4 T cells, we evaluated their expression of Bcl-2 protein. As infection progresses, the expression of Bcl-2 among CD4 T cells declines and drops further when CD4 T cells are restimulated through the TCR in vitro. These results suggest that this CD4 T cell immunodeficiency in MAIDS includes a TCR-induced program of activation-induced cell death and an uncoupling from cytokine synthesis pathways and proliferation of CD4 T cells. The decline in Bcl-2 expression may be in part responsible for this reprogramming.
CD28 costimulation prevents cell death during primary T cell activation.
Authors: Noel P J , Boise L H , Green J M , Thompson C B
Published: December 2022

CD28 has been demonstrated to play an important role in augmenting T cell proliferation and effector function. Costimulation through CD28 has also been reported to enhance human T cell survival. in this report, we have further investigated the role of CD28 in regulating T cell survival by comparing the survival characteristics of T cells from wild-type and CD28-deficient mice. CD28 costimulation of anti-CD3-activated cells augmented the viability of T cells from wild-type but not from CD28-deficient mice. CTLA4Ig treatment reduced wild-type T cell viability to a level comparable with CD28-deficient T cells. The ability of CD28 to enhance survival during T cell activation correlated positively with its ability to up-regulate the protein product of the cell survival gene bcl-xL. No differences in the expression of either Bcl-2 or Fas were observed between wild-type and CD28-deficient T cells. The CD28-dependent enhancement of cell survival during in vitro activation was found to be independent of Fas expression, as CD28 costimulation enhanced T cell survival to comparable levels in both wild-type and lpr animals. Cell death in CD28-deficient animals and in wild-type animals treated with CTLA4Ig displayed the morphologic characteristics of apoptosis. Additionally, inhibitors of ICE proteases could reverse cell death induced by TCR engagement in the absence of CD28 costimulation. Thus, CD28 costimulation not only enhances the proliferative expansion of cells activated through the TCR but also increases the likelihood that individual cells survive during T cell activation.
Characterization of a T cell line specific to an anti-Id antibody related to the carbohydrate antigen, sialyl SSEA-1, and the immundominant T cell antigenic site of the antibody.
Authors: Tsuyuoka K , Yago K , Hirashima K , Ando S , Hanai N , Saito H , Yamasaki K M , Takahashi K , Fukuda Y , Nakao K , Kannagi R
Published: December 2022

The stage-specific embryonic Ag-1 (SSEA-1) is a carbohydrate Ag and regarded as an onco-developmental Ag. Sialyl SSEA-1 Ag, the sialylated form of SSEA-1, is frequently expressed in human cancer cells as well as in murine cancer cells. A mAb, FH-6, was shown to specifically recognize the Ag. We have generated five anti-Id Abs directed to the paratope-related idiotopes of the FH-6 Ab. One of these anti-Id Abs, Id-F2, increased the survival of host mice that were inoculated with Meth-A cells expressing the sialyl SSEA-1 Ag. To clarify the exact mechanism underlying the antitumor effect of the anti-Id Ab, we established a T cell line that recognized Id-F2 in association with MHC class II molecules. The T cell line was CD4+V beta 8+, and produced IL-2, exhibiting helper activity for B cells. The VH CDR2 region of the Id-F2 amino acid sequences turned out to be strongly immunogenic to T cells. When the immune complexes, consisting of the sialyl SSEA-1 Ag, FH-6, and Id-F2, were formed at the Meth-A cell-surface, the T cell line showed a strong proliferative response. The possible roles played by such T cell subsets in the anti-tumor effect are discussed.
In the absence of endogenous IL-10, mice acutely infected with Toxoplasma gondii succumb to a lethal immune response dependent on CD4+ T cells and accompanied by overproduction of IL-12, IFN-gamma and TNF-alpha.
Authors: Gazzinelli R T , Wysocka M , Hieny S , Scharton-Kersten T , Cheever A , Kühn R , Müller W , Trinchieri G , Sher A
Published: December 2022

To examine the function of IL-10 synthesis during early infection with the intracellular protozoan Toxoplasma gondii, IL-10 knockout (KO) mice were inoculated with an avirulent parasite strain (ME-49). In contrast to control littermates that displayed 100% survival, the IL-10-deficient animals succumbed within the first 2 wk of the infection, with no evidence of enhanced parasite proliferation. The mortality in the IL-10 KO mice was associated with enhanced liver pathology characterized by increased cellular infiltration and intense necrosis. Levels of IL-12 and IFN-gamma in sera of infected IL-10-deficient animals were four- to sixfold higher than those in sera from control mice, as were mRNA levels for IFN-gamma, IL-1 beta, TNF-alpha, and IL-12 in lung tissue. Similarly, macrophages from IL-10 KO mice activated in vitro or in vivo with T. gondii produced higher levels of TNF-alpha and IL-12 than macrophages from control animals. Moreover, spleen cells from IL-10 KO mice infected with T. gondii secreted more IFN-gamma than splenocytes from nondeficient animals. In vitro depletion experiments indicated that CD4+ lymphocytes are the major source of the latter cytokine in the spleen cell populations, and in vivo depletion with anti-CD4 Abs protected the IL-10 KO mice from parasite-induced mortality. Together the data suggest that endogenous IL-10 synthesis plays an important role in vivo in down-regulating monokine and IFN-gamma responses to acute intracellular infection, thereby preventing host immunopathology.
Human Thy-1 is cytokine-inducible on vascular endothelial cells and is a signaling molecule regulated by protein kinase C.
Authors: Mason J C , Yarwood H , Tárnok A , Sugars K , Harrison A A , Robinson P J , Haskard D O
Published: December 2022

Thy-1 is a glycosylphosphatidylinositol-anchored member of the Ig superfamily whose function, particularly in the human, remains unknown. We have demonstrated that human Thy-1 is expressed on endothelial cells (EC) both in situ and on the surface of cultured human umbilical vein EC and dermal microvascular EC (DMEC). The expression of the molecule decreased with serial passage but was restored by treatment of EC with PMA and phorbol-12,13-dibutyrate (PBu), which increased Thy-1 by up to 100-fold in a dose-dependent manner. This increase was first detectable at 12 h post-stimulation, peaked at 48 h, and was maintained at 72 h. In PBu-stimulated DMEC, Western blotting revealed Thy-1 to be a 29-kDa molecule, while Northern analysis demonstrated an increase in steady-state Thy-1 mRNA. Thy-1 expression was also induced on DMEC by treatment with TNF. Inhibition studies showed that the induction of Thy-1 by PBu and TNF was protein synthesis dependent. The up-regulation of Thy-1 by PBu, but not TNF, was inhibited by the protein kinase C inhibitor RO31-8220, suggesting the presence of protein kinase C-dependent and -independent pathways for Thy-1 expression. To investigate the function of Thy-1 on human EC, we studied changes in intracellular calcium concentration ([Ca2+]i) following cross-linking of Thy-1 on human umbilical vein EC. This resulted in a rapid transient rise of [Ca2+]i in EC. Our results demonstrate for the first time the presence of Thy-1 on cultured human EC. The expression on EC, the inducibility by TNF, and the ability to transmit signals suggest that Thy-1 may have an important role in inflammatory responses.
A pathogenic role for gamma delta T cells in relapsing-remitting experimental allergic encephalomyelitis in the SJL mouse.
Authors: Rajan A J , Gao Y L , Raine C S , Brosnan C F
Published: December 2022

Previous studies have detected gamma delta T cells in multiple sclerosis and experimental allergic encephalomyelitis (EAE) lesions but their role remains obscure. In the present study, we assessed gamma delta T cell dynamics and distribution in spleen and central nervous system (CNS) from mice with relapsing-remitting EAE, and studied the effect of depleting these cells on clinical and pathologic expression of disease using the mAb GL3. By immunohistochemistry and FACS analysis, striking disease-related changes were observed in the gamma delta T cell population in the CNS. FACS analysis showed that while gamma delta T cells remained low in the spleen (approximately 2% total CD3+ T cells) at all stages, in the CNS they increased to approximately 12% at the height of the acute attack, fell to approximately 5% during the recovery phase, but rose again to approximately 12% during the chronic phase. In animals in which gamma delta T cells were depleted immediately before the onset of acute disease, or during the chronic stage, a striking and significant reduction in the severity of the clinical signs was observed that was associated with a decrease in the percentage of CD3+/gamma delta T cells in the CNS. In depleted animals a statistically significant reduction in inflammation and demyelination was noted during the acute stage, but only marginal effects on these disease parameters were found in the chronic phase. Taken together, the data support the conclusion that gamma delta T cells play an important role in the pathogenesis of EAE in mice during both acute and chronic/progressive phases of the disease process.
Human IgG monoclonal antibodies that modulate the binding of specific IgE to birch pollen Bet v 1.
Authors: Visco V , Dolecek C , Denépoux S , Le Mao J , Guret C , Rousset F , Guinnepain M T , Kraft D , Valenta R , Weyer A , Banchereau J , Labecque S
Published: December 2022

Birch pollen allergy is a very frequent pathology in Europe and North America. More than 95% of the tree pollen allergic patients display IgE reactivity against Bet v 1, the major birch pollen allergen. Starting with PBL from a patient desensitized by immunotherapy, we have generated five B cell lines (BAB1 to BAB5) that secrete human IgG mAbs of high affinity for Bet v 1. Although competition studies indicated that these human IgG mAb recognized different epitopes, broad cross-reactivity was found with Bet v 1 homologous allergens present in tree pollens and plant-derived foods. When tested for interference with allergic patients' IgE, BAB1 inhibited (by 80-100%) the binding of IgE to nitrocellulose-blotted Bet v 1, while BAB2 enhanced it. The biologic significance of the ability of BAB1 to interfere with patients' IgE binding is indicated by the finding that BAB1 completely inhibited Bet v 1-induced histamine release from allergic patients' basophils. Allergen-specific human IgG mAbs such as BAB1, which presents high blocking activity in both immunochemical and cellular IgE competition experiments, might have therapeutical application.
Cellular and molecular factors that regulate the differentiation and apoptosis of germinal center B cells. Anti-Ig down-regulates Fas expression of CD40 ligand-stimulated germinal center B cells and inhibits Fas-mediated apoptosis.
Authors: Choe J , Kim H S , Zhang X , Armitage R J , Choi Y S
Published: December 2022

To investigate the molecular and cellular mechanisms underlying the selection, differentiation, and apoptosis of germinal center (GC) B cells, we have established a culture system containing a follicular dendritic cell (FDC) line, HK. The mAb, 3C8, which is specific to HK cells and recognizes dendritic network in the GC, was developed and provided additional evidence that HK cells are related to FDC by sharing a unique surface Ag. The roles for CD40 ligand (CD40L) and T cell-derived cytokines in the differentiation of GC B cells were investigated in our culture system. We show that there are two distinct stages of GC B cell differentiation. In the early stage, GC B cells undergo spontaneous apoptosis unless they are stimulated by CD40L. In the secondary stage, IL-10 directs GC B cell differentiation toward the generation of plasma cells, while the absence of IL-10 stimulation leads to the generation of memory B cells. The major function of CD40L was found in the enhancement of cell recovery and the augmentation of memory B cell generation. Although GC B cells are Fas+, GC B cells are at first resistant to, but then become sensitive to, anti-Fas killing after 24 h in culture with CD40L, which coincides with the gradual increase in Fas expression on GC B cells. Furthermore, anti-Ig down-regulated Fas expression on CD40L-stimulated GC B cells, suggesting that Ag receptor engagement down-regulates Fas expression and prevents Fas-mediated apoptosis of GC B cells. Our data imply that GC T cells have an important role in the differentiation and apoptosis of GC B cells. GC T cells expressing both CD40L and Fas ligand have a dual function on GC B cells, helper or killer, depending on the status of target B cells. In the early stage, GC T cells stimulate the extensive proliferation of GC B cells, ensuring a large repertoire of B cells for selection. In the later stage, GC T cells kill B cells via Fas-Fas ligand interactions unless GC B cells are positively selected by Ags present on FDC.