bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diversity of novel recombining elements suggests developmentally programmed expression of the T cell receptor α/δ locus
Authors: Arden Bernhard 
Published: March 2007

AbstractDuring fetal ontogeny, the first wave of γδ T lymphocytes appears in the thymus at day 14 of gestation assembling predominantly T cell receptors (TcR) with Vγ3 and Vδ1. To identify Vδ gene segments that are transcribed at day 16, subsequent to the first wave of Vδ1 expression, δ chain cDNA was amplified by the anchored polymerase chain reaction with single‐sided specificity for Cδ. Unexpectedly, most of the cDNA clones do not contain V gene segments. In some cDNA clones an alternative splice from the leader exon to the Cδ exon has deleted the whole variable region exon. In other cDNA clones, multiple non‐V‐like elements are juxtaposed to the Dδ2 and Jδ1 gene segments. A large number of these diverse elements appear to be rearranged in fetal thymocytes, bringing Vα gene segments located upstream of the recombining element into proximity to the Jα locus. It is proposed that these rearrangements make irreversiblethe commitment to the TcR αβ lineage and determine a programmed read out of different clusters of Vα gene segments.
Among naive precursor cell subpopulations only progenitors of memory B cells originate germinal centers
Authors: Linton Phyllis‐Jean , Lo David , Lai Lily , Thorbecke G. Jeanette , Klinman Norman R. 
Published: March 2007

AbstractImmunization leads to the generation of both antibody‐forming cells (AFC) and memory B cells which are thought to arise in germinal centers within lymphoid follicles. The findings that the precursors to memory B cells reside in the J11Dlo subpopulation of the spleens in non‐immune mice and that this subpopulation is distinct from conventional AFC precursors, including CD5+ B cells, suggest that the precursors of germinal centers might also reside in the J11Dlo subpopulation. To test this hypothesis, SCID mice were repopulated with CD4+ carrier‐primed T cells and T‐depleted J11Dlo, J11Dhi or CD5+ B cells and immunized with a hapten‐carrier conjugate. Only the J11Dlo population was enriched for cells that produced germinal centers. Thus, the subpopulation of precursors that generates memory B cells also originates germinal centers.
Enrichment of primary lymphocyte‐supporting stromal cells and characterization of associated B lymphocyte progenitors
Authors: Funk Phillip E. , Witte Pamela L. 
Published: March 2007

AbstractStudies of Whitlock/Witte long‐term bone marrow cultures have revealed the necessity of two cell types for B lymphopoiesis, a stem cell and the stromal cell. While a number of stromal cell lines exist they have been found to be heterogeneous with respect to cell surface marker expression and growth factor production. Separation and analysis of fresh bone marrow stromal cells is, therefore, necessary to understand the regulation of lymphopoiesis in vivo. Here we report the early stages of such studies. We demonstrate that stromal cells, as assessed by morphology and alkaline phosphatase reactivity after short‐term culture, are enriched in cellular aggregates that can be separated from bone marrow suspensions. Stromal cells are present in aggregates at a frequency of one per thousand cells, whereas marrow from which the aggregates have been removed contains only one stromal cell per fifty‐thousand cells. These aggregates are able to form Whitlock cultures from greatly reduced numbers of initiating cells, indicating that they contain culturable B lineage precursors as well as stromal cells capable of supporting B lymphopoiesis. The aggregates appear to be naturally formed and provide a means to examine native B cell precursor‐stromal cell contacts. We find little evidence for sequestering of late‐stage B cell precursors within the aggregates. Terminal deoxynucleotidyl transferase‐positive cells, on the other hand, are approximately three times more frequent in bone marrow aggregates, suggesting close contact between very early B cell progenitors and stromal cells within the aggregates. The finding that stromal cells are enriched in cellular aggregates is an important first step in the ultimate isolation of these cells from marrow suspensions, which is vital to understanding stromal cell function in vivo.
Peptide recognition, T cell receptor usage and HLA restriction elements of human heat‐shock protein (hsp) 60 and mycobacterial 65‐kDa hsp‐reactive T cell clones from rheumatoid synovial fluid
Authors: Quayle Alison J. , Wilson Kay Black , Li Shu Guang , Kjeldsen‐Kragh Jens , Oftung Fredrik , Shinnick Thomas , Sioud Mouldy , Førre Øsystein , Capra J. Donald , Natvig Jacob B. 
Published: March 2007

AbstractA commonly held postulate regarding the etiology of rheumatoid arthritis (RA) is that of antigenic mimicry. Recent interest has focused on the mycobacterial 65‐kDa heat‐shock protein (hsp) as a putative causal agent. The 65‐kDa hsp has over 40% sequence homology with the human hsp 60, and elevated synovial T cell responses to both antigens have been demonstrated in RA and juvenile rheumatoid arthritis patients. Such T cells should, therefore, be specific for shared epitopes on the two antigens. To investigate this, we screened synovial fluid mononuclear cells from two early RA patients with peptides of the 65‐kDa hsp which have the greatest homology with the human hsp 60. We also raised a panel of T cell clones from one of the patients with the 65‐kDa hsp. The synovial T cell population from both patients and one of the T cell clones recognized a peptide representing the amino‐acid sequence 241–255. This clone also responded to the peptide of the equivalent human sequence, and was restricted by HLA‐DQ. A second T cell clone recognized an adjacent epitope (amino acid sequence 251–265) which is also highly homologous with the human sequence, but this clone was restricted by HLA‐DR. The clones utilized different Vβ gene segments but the same Dβ and Jβ gene elements, and both exhibited specific cytotoxicity against autologous antigen‐pulsed macrophages. Our findings, therefore, do not disagree with the postulate that autoimmune disease could possibly be triggered by bacterial epitopes with homology to self protein. However, it is also noted that there are alternative interpretations of this data.
Induction of high‐affinity paf receptor expression during T cell activation
Authors: Calabresse Cynthia , Nguer Momar Cheik , Pellegrini Olivier , Benveniste Jacques , Richard Yolande , Thomas YolèNe 
Published: March 2007

AbstractActivated human T cells via the CD2 or the CD3 pathways exhibited a higher capacitythan resting T lymphocytes to incorporate and metabolize [3H] pafacether (paf) at 37°C. Resting T lymphocytes lacked specific binding capacity for paf, yet high‐affinity paf receptors (paf‐R) were inducedon CD3‐ or CD2‐dependent activation. This up‐regulation in the number of paf‐R became apparent by day 1 of culture, reached a maximum of about 25000 sites cell by days 4 to 6 and subsequently declined. Interestingly, human recombinant interleukin‐2 in a dose‐dependent manner prevented the decrease of high‐affinity paf‐R expression on T cells. By contrast, the receptor affinitywas constant throughout the culture period. Thus, paf‐R at different stages of Tcell activation were indistinguishable with respect to receptor‐ligand interaction, and differed only in their number. Together, these data demonstrate that after activation human T cells develop membrane high‐affinity paf‐binding sites. They also suggest for the first time that expression of the paf‐R are coupled to T cell activation and/or differentiation.
Non‐additive effects of multiple amino acid substitutions on antigen‐antibody recognition
Authors: Mateu Mauricio G. , Andreu David , Carreno Cristina , Roig Xavier , Cairó Jordi‐Joan , Camarero Julio A. , Giralt Ernest , Domingo Esteban 
Published: March 2007

AbstractSynthetic peptides have been used to mimic the main antigenic site of foot‐and‐mouth disease virus (FMDV) of serotype C and of several variant isolates. This region includes multiple continuous B cell epitopes. The effect of single amino acid replacements, individually or in combination, on antigen specificity has been evaluatedusing monoclonal antibodies. Quantitative enzyme immunodot assays have shown that both additive and non‐additive effects of multiple replacements occur in continuous Bcell epitopes, with regard to antibody recognition. Antigenically critical single replacements may be compensated by other, non‐critical replacements. Thus, the role of a single amino acid on antibody recognition depends on the sequence context in the antigenic domain. The non‐additive effects of multiple replacements may modulate the extent of antigenic diversification of highly variable RNA viruses, and keep virusesconfined within antigenic groups by precluding linear antigenic divergence.
Interleukin‐1 induces protein tyrosine phosphorylation in T cells
Authors: Mũnoz Eduardo , Zubiaga Ana , Huang Chi‐Kuang , Huber Brigitte T. 
Published: March 2007

AbstractInterleukin (IL)‐1α activates multiple signal transmission pathways inthe T helper type 2 cell line, D10A, and these pathways are linked to two separate IL‐1 receptors (IL‐1R). In the present report we show that IL‐1 induces the activation of tyrosine kinase in these cells, leading to tyrosine phosphorylationof a subset of proteins of 38, 75, 97 and 115 kDa. This type of phosphorylation is prevented by a monoclonal antibody directed against the 80‐kDa IL‐1R and by tyrphostins which are specific inhibitors of tyrosine kinases. In addition, this inhibitor blocks IL‐1‐ and IL‐2‐induced proliferation in D10A cells as well as the c‐myc and c‐myb proto‐oncogene mRNA expression inresponse to IL‐1. Interestingly, the inhibitor of cAMP‐dependent kinase, H‐8, only blocks IL‐1‐induced c‐myb, but not c‐myc mRNA expression. Altogether, our results demonstrate that the activation of a tyrosine kinase(s) is an early and major event that happens after IL‐1/IL‐1R interaction, leading to an increase in intracellular cAMP which results in c‐myb and IL‐5 mRNA expression. Independent of cAMP, by tyrosine phosphorylation of specific substrates IL‐1 also induces c‐myc andIL‐6 mRNA expression and cellular proliferation.
Cytokine enhancement of complement‐dependent phagocytosis by macrophages: synergy of tumor necrosis factor‐α and granulocyte‐macrophage colony‐stimulating factor for phagocytosis of Cryptococcus neoformans
Authors: Collins Helen L. , Bancroft Gregory J. 
Published: March 2007

AbstractWe have examined the regulation of complement dependent phagocytosis by macrophage‐activating cytokines. Tumor necrosis factor (TNF)‐α and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), but not interferon‐γ, interleukin‐4 or macrophage‐CSF, stimulated ingestion of the encapsulated fungal pathogen Cryptococcus neoformans by resident peritoneal macrophages in vitro. This was dependent upon opsonization of the yeasts with complement, 72 h of incubation with the cytokines for maximum effect, and the obligate involvement of the macrophage CR3 receptor. TNF‐α and GM‐CSF synergized at low concentrations, resulting in dramatic up‐regulation of phagocytosis when compared to either cytokine alone. Supernatants from C. neoformans‐specific T cells also increased macrophage phagocytic efficiency. Finally, the administration ofneutralizing mAb specific for TNF‐α and GM‐CSF increased mortality in C. neoformans‐infected mice, and induced the rapid progression of disease with involvement of the brain and meninges. We conclude that TNF‐α andGM‐CSF are potent regulators of complement‐dependent phagocytosis by murine macrophages. Macrophage activation with these two cytokines can completely overcome the anti‐phagocytic properties of the virulent yeasts. Our results, therefore, implicate TNF‐α and GM‐CSF as important mediators of resistance to encapsulated pathogens such as C. neoformans where ingestion of the organism is acritical process in host resistance.
Membrane molecules which trigger the production of interleukin‐1 and tumor necrosis factor‐α by lipopolysaccharide‐stimulated human monocytes
Authors: Couturier Christine , Jahns Gerlinde , Kazatchkine Michel D. , Haeffner‐Cavaillon Nicole 
Published: March 2007

AbstractWe have investigated the role of the membrane molecules CD11/CD18 and CD14 whichmay mediate the binding of lipopolysaccharide (LPS) to human monocytes, in the induction of the production and release of interleukin (IL)‐1 and tumor necrosis factor‐α (TNF‐α) by LPS‐stimulated cells. Blockade of CD11a, CD11b and CD18 with saturating concentrations of specific mAb did not inhibit the releaseof cytokines from LPS‐stimulated monocytes. In contrast, inhibition of the release of IL‐1β and TNF‐α occurred in monocytes cultures that had been pretreated with either of two monoclonal antibodies (mAb) recognizing different epitopes on the CD14 molecule. The binding of LPS to CD14 has been previously shown to require serum factors. In the present study, we found that serum had an enhancing effect on the release of IL‐1 and TNF‐α from LPS‐stimulated cultures of normal human monocytes. The inhibitory effect of anti‐CD14 mAb was, however, observed in cultures performed in the presence or in the absence of serum, suggesting that triggering of IL‐1/TNF‐α release by CD14 is independent of LPS‐binding proteins or other serum proteins. IL‐1β and TNF‐α were also released from LPS‐stimulated cultures of monocytes from patients with paroxysmal nocturnal hemoglobinuria lacking expression of CD14. Thus, CD14 but notCD11/CD18 can trigger serum‐dependent and independent cytokine release from endotoxin‐stimulated normal human monocytes; CD14 is not, however, the only LPS receptor that is involved in the secretory response of endotoxin‐stimulated cells.
Both LFA‐1‐positive and ‐deficient T cell clones require the CD2/LFA‐3 interaction for specific cytolytic activation
Authors: Kemenade Elly Van De Wiel‐van , Te Velde Anje A. , De Boer Annemiek J. , Weening Ron S. , Fischer Alain , Borst Jannie , Melief Cornelis J. M. , Figdor Carl G. 
Published: March 2007

AbstractWe investigated the capacity of T lymphocytes from a leukocyte adhesion‐deficient (LAD) patient to respond to alloantigen. Leukocytes of this patient completely lacked LFA‐1 surface expression due to the absence of mRNA coding for theLFA‐1 β chain. Despite the absence of LFA‐1, T lymphocytes obtained from this patient, cultured with allogeneic stimulator cells (lymphoblastoid B cells JY), were capable of lysing JY cells. Furthermore, two T cell clones (one CD4+ and one CD8+), generated from this lymphocyte culture, specifically lysed theallogeneic lymphoblastoid JY cells. The cytolytic capacity of LFA‐1‐negative T lymphocytes and T cell clones was comparable to that of control LFA‐1‐positive T cells with allospecificity against JY. Detailed analysis of the CD4 positive and LFA‐1‐negative T cell clone demonstrated that it specifically recognized HLA‐DQ. Antibody inhibition studies showed that the CTL/target cell interaction was mediated through the CD2/LFA‐3 adhesion pathway. LFA‐1 expressed by the target cells did not participate in the CTL/target cell conjugate formation and contributed only minimally to the cytotoxic activity. Moreover, when allogeneic LFA‐1‐deficient B cells, bearingthe appropriate HLA‐DQ alloantigen, were used as target cells, significant levels of specific cytotoxicity were measured, further excluding a role for LFA‐1 in this interaction. The adhesion molecules, VLA‐4, CD44 and L‐selectin (LECAM1) were not involved.These results demonstrate that LFA‐1‐negative T lymphocytes can exert allospecific cytotoxicity and that CTL/target cell contact is mediated through the CD2/LFA‐3 route. This observation may explain in part why in LAD patients viralinfections, cleared largely by T cells, are less frequently observed than bacterial infections, in which phagocytic cells play a major role.
HLA‐DR peptide‐induced alloreactive T cell lines reveal an HLA‐DR sequence that can be both “dominant” and “cryptic”: evidence for allele‐specific processing
Authors: de Koster H. Saskia , Rood Jon J. Van , Termijtelen Annemarie 
Published: March 2007

AbstractPreviously, we reported on a T cell line, ThoU6, which we obtained through stimulation of DPw3+ cells with a synthetic” DR3 peptide “ with a sequence identical to the third hypervariable region of the DRB1*0301 chain. This T cell line recognizes both the synthetic peptide presented by DPw3 as well as DR3+ DPw3+ stimulator cells. This implies that the synthetic DR3 peptide has a natural counterpart in DR3‐positive cells. Here we describe the recognition pattern of another T cell line that was sensitized with the same synthetic DR3 peptide. This T cell line, BieU6, shows both HLA‐DRw13/Dw18 (self)‐restricted recognition of the synthetic DR3 peptide and allorecognition towards DR13/Dw19, a molecule which is highly homologous to Dw18, in the absence of synthetic peptide. These results suggest that the epitope formed by the Dw18 molecule plus the synthetic DR3 peptide and recognized by T cell line BieU6 mimics the Dw19 molecule. The potential role for a Dw19‐specific peptide is discussed. The inability of T cell line BieU6 to recognize Dw18+ DR3+ cellsindicates that, in this case, the synthetic DR3 peptide is “cryptic”, i.e. does not have a natural counterpart that is effectively presented to T cells. Mapping of the shortest peptides recognized by T cell lines ThoU6 and BieU6 indicate thatthese sequences are fully overlapping. We, therefore, suggest that the antigen‐presenting molecules, HLA‐DPw3 and HLA‐Dw18, differ in their accessibilityfor self peptides derived from the third hypervariable region of DR molecules. These observations may be explained by allele‐specific processing.
T cell responses to human recombinant acetylcholine receptor‐α subunitin myasthenia gravis and controls
Authors: Sun Jia‐Bin , Harcourt Gillian , Wang Zeng‐Yu , Hawke Simon , Olsson Tomas , Fredrikson Sten , Link Hans 
Published: March 2007

AbstractAntibodies against the nicotinic acetylcholine receptor (AChR) of the neuro‐muscular junction are detectable in most patients with myasthenia gravis (MG) and assumed to participate in the destruction of the AChR, thereby, causing the characteristic signs and symptoms of the disease. The extent and importance of T cell responses to AChRand its subunits in MG are still unsettled. We have now examined T cell reactivities using human recombinant AChR‐α subunit as antigen. Upon recognition of appropriate antigen in an MHC‐class II‐restricted fashion, memory T cells secrete interferon‐γ (IFN‐γ). Adopting this principle in an immunospot assay we found that 73% of MG patients had recombinant human AChR‐α subunit‐reactive T cells at a median value of 1 per 56000 blood mononuclear cells, while only 27% of the MG patients responded to the α subunit in a conventionallymphocyte proliferation assay. This compares with even lower numbers of AChR‐reactive T cells and 14% positivity in the proliferation assay among control subjects. The T cell responses to the control antigens purified protein derivative and myelin basicprotein did not differ between MG and controls, underlining the specificity of an augmented T cell reactivity to AChR‐α subunit in MG. α Subunit‐specific T cell lines and clones propagated from patients with MG and healthy controls yielded a high proportion of α subunit‐reactive T cells in the IFN‐γ immunospot aassay. Their appearance was inhibited by the addition of monoclonal anti‐MHC class II antibodies, demonstrating that an MHC‐restricted T cell response was measured. Our data underline that the AChR‐α subunit is a major T cell autoantigen in MG.
Non‐random features of the repertoire expressed by the members of one Vx gene family and of the V‐J recombination
Authors: Milstein César , Even Jos , Jarvis John M. , Gonzalez‐Fernandez Africa , Gherardi Ermanno 
Published: March 2007

AbstractThe 5' and 3' flanking sequences of 14 members of the VxOx (VK 4/5) gene family of BALB/c mice have been established. The family was unusual in the number of bases between the codon for Pro 95 and the heptamer sequence; most members contained four but there were also examples of none. A conserved leader sequence was used toamplify the genomic DNA of rearranged genes in order to analyze the spleen B cell repertoire of non‐immunized animals. The library contained many members with virtually identical sequences to one or other of the already known members of the family. In addition, there were repeats of other sequences, allowing the definition of 12 hitherto undefined members of the family. Only 3 out of 96 could have originated by gene conversion, or as artefacts of the amplification procedure, and only 2 were putative somatic mutants.The frequency of expression of different members of the VxOx gene family was not random, and some germ‐line genes were unrepresented in the library. The high frequency of VxOx1‐Jx5 is in line with the dominance of this combination in the oxazolone response.An analysis of the junctional segment showed that although in most cases the diversity was due to trimming, there were exceptions indicating de novo additions (N or P bases). The average number of bases trimmed from the Vx and the Jx segments was not the same. There was no correlation in the number of bases trimmed from Vx or Jx in each recombination. The implications of asymmetric trimming in terms of the mechanism of recombination are discussed.
Cytotoxic T lymphocytes against the antigen‐processing‐defective RMA‐S tumor cell line
Authors: Sijts Alice J. A. M. , De Bruijn Marloes L. H. , Nieland John D. , Kast W. Martin , Melief Cornelis J. M. 
Published: March 2007

AbstractRMA‐S is an antigen processing‐defective cell line, obtained from a Rauscher virus‐induced tumor. The cells express only a low level of cell surface major histocompatibility complex (MHC) class I molecules, which are supposed to be devoid of internally derived antigenic peptides. We investigated Rauscher virus expression and Rauscher peptide presentation to virus‐specific cytotoxic T lymphocytes (CTL) by this cell line. Viral proteins are expressed properly, both intracellularly and atthe cell surface of RMA‐S. Rauscher peptides are presented tovirus‐specific CTL in the groove of both the class I H2Kb and Db molecules, but at a low level. Culture of RMA‐S cells at room temperature increases theirsusceptibility to CTL. The RMA‐S defect thus affects, but not totally abrogates, Rauscher peptide presentation by MHC class I molecules via the endogenous pathway. Thisindicates that the RMA‐S antigen processing deficit is not absolute.
A cross‐species functional interaction between the murine major histocompatibility complex class I α3 domain and human CD8 revealed by peptide‐specific cytotoxic T lymphocytes
Authors: Moots Robert J. , Samberg Nancy L. , Pazmany Laszlo , Frelinger Jeffrey A. , McMichael Andrew J. , Stauss Hans J. 
Published: March 2007

AbstractThe monomorphic cell surface glycoprotein CD8 acts as co‐receptor in the recognition of peptide‐major histocompatibility complex (MHC) class I complexes by cytotoxic lymphocytes (CTL) by binding to the monomorphic α3 domain of the class I molecule. Positions 227 and 245 in the class I α3 domain appear to be especially important for this interaction. Recent reports suggest there is no interspecies recognition between CD8 and MHC class I.In this study, hybrid genes from human class I HLA‐A0201 and murine class I H2Kb were transfected into human and mouse cells and tested in Cr‐release assays using HLA‐A0201‐restricted influenza A matrix peptide‐specific CTL as effectors. Transfected cells expressing chimeric genes comprising the α1 and α2 domains from HLA‐A0201 together with the H2Kb α3 domain were lysed as effectively as wild‐type HLA‐A0201 and in both cases, killing was blocked by anti‐CD8 antibodyequally well. These results indicate that human CD8 can interact with the α3 domain of murine class I to the same level as human class I.