bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antigen presentation for T cell interleukin‐2 secretion is a late acquisition of neonatal B cells
Authors: Morris Jennifer F. , Hoyer Jeffry T. , Pierce Susan K. 
Published: March 2007

AbstractThe ability of B lymphocytes to process and present antigen to helper T cells is essential to initiate T cell‐B cell interactions in humoral immune responses. Here we describe the developmental acquisition of the antigen‐presenting function of B cells as measured by the ability of B cells to stimulate a T cell hybrid to interleukin (IL)‐2 secretion. Neonatal splenic B cells are not adult‐like in their ability to process and present the model protein antigen pigeon cytochrome (Pc), which enters the B cell through fluid‐phase pinocytosis, until 21 to 28 days of life. The ability of neonatal B cells to process and present antigen which enters the cell bound to surface Ig is not adult‐like until 28 days of age. When neonatal B cells acquire antigen‐presenting cell (APC) function, surface IgM facilitates antigen processing. The delayed acquisition of APC function cannot be accounted for solely by a deficiency in major histocompatibility complex MHC class II, ICAM‐1, or LFA‐1 as neonatal B cells express adult levels of these molecules by 7–14 days after birth. Moreover, the ability of neonatal B cells to present a peptide fragment of Pc which does not require processing is adult like by day 14. Furthermore, neonatal B cells are capable of binding, internalizing and degrading radiolabeled antigen, suggesting a more subtle level of regulation. In contrast to neonatal B cells, immature B cells in the adult bone marrow and adult B cells undergoing antigen‐driven differentiation to memory B cells, as defined by the loss of the J11D marker, are competent to process and present antigen resulting in T cell IL‐2 secretion. Thus, developing B cell subpopulations in the adult and in the neonate can be distinguished. Only neonatal B cells are deficient in their ability to stimulate T cells to IL‐2 production.
Use of Torpedo‐mouse hybrid acetylcholine receptors reveals immunodominance of the α subunit in myasthenia gravis antisera
Authors: Loutrari Heleni , Tzartos Socrates J. , Claudio Toni 
Published: March 2007

AbstractThe nicotinic acetylcholine receptor (AChR), a pentameric complex of α2βγδ subunits, is the autoantigen in the human autoimmune disease myasthenia gravis (MG). Anti‐AChR antibodies are found in ∼90% of MG patients and using indirect methods (competitive binding to solubilized AChR), peptides, or synthetic peptides, the majority of these antibodies have been shown to bind to the AChR α subunit. In order to determine directly the AChR subunit specificities of MG antibodies, we employed as antigens a novel set of hybrid AChR composed of species cross‐reacting and non‐cross‐reacting subunits stably expressed in fibroblasts. Sequence similarities of homologous subunits among species can vary widely, with mammalian subunits having 87 %‐96 % identity and Torpedo‐mammalian subunits having 54 % −80 % identity. These findings are reflected in antigenic specificities, with human anti‐AChR antisera frequently recognizing mouse AChR but rarely recognizing Torpedo. By establishing separate cell lines stably expressing all‐Torpedo, all‐mouse, and different combinations of Torpedo and mouse subunits, we were able to provide the first direct evidence of a predominant anti‐α subunit specificity in MG antisera. Functional hybrid AChR stably expressed in an intact cell membrane provide us, with a system that best mimics the in vivo environment of the MG antibody in a binding assay. Such a system allows us to investigate a perplexing observation in the field: a poor correlation between the patient's clinical status and antibody titer. Those antibodies which can interfere with AChR function, such as ones with the ability to cross‐link AChR and induce their accelerated internalization and degradation (antigenic modulation) might represent a subpopulation of MG antibodies important in disease induction or maintenance. In this report, we demonstrate that wild‐type and hybrid AChR expressed in fibroblasts can be antigenically modulated by intermolecular cross‐linking antibodies as AChR are in native muscle cells. Because we can monitor dynamic interactions between AChR and MG antibodies, this system may allow us to define crucial pathogenic epitopes in MG by expressing hybrid, chimeric, and mutant AChR.
Evidence for an association between the T cell receptor/CD3 antigen complex and the CD5 antigen in human T lymphocytes
Authors: Osman Narin , Ley Steven C. , Crumpton Michael J. 
Published: March 2007

AbstractIn this work we report that CD5, a T cell accessory activation antigen and receptor for the B cell surface protein CD72, is associated with the T cell antigen receptor (TcR)/CD3 complex in human T lymphocytes. In vitro phosphorylation of either CD3 or CD5 immunoprecipitates prepared from CD3‐stimulated Jurkat and peripheral blood T cells in the presence of the detergent polyoxyethylene 10 oleyl ether (Brij96) showed, unexpectedly, an identical pattern of five phosphopolypeptides of 70, 59, 56, 21 and 18 kDa, respectively. Peptide mapping of the five bands demonstrated that the same protein kinase substrates co‐precipitated with both CD3 and CD5 and that the majority of the protein phosphorylation occurred on tyrosine residues. These data suggested that the TcR/CD3 complex and and the CD5 antigen might be associated in T cells. Evidence to support this hypothesis was obtained from analysis of immunoprecipitates prepared from surface‐iodinated T cells. Bands characteristic of the TcR and CD3 antigens were identified in CD5 immunoprecipitates and conversely, CD5 was identified in CD3 immunoprecipitates. Conformation that CD3 and CD5 co‐precipitated in the presence of Brij96 was obtained by Western blotting. Quantitative immunodepletion demonstrated that between 10 % –20 % of cell surface CD5 was associated with the TcR/CD3 complex in Brij96 detergent lysates of human T cells and, furthermore, that this association was independent of T cell activation. The association of these two receptors provides a possible physical basis for the accessory role of the CD5 antigen in T cell activation.
Functional and molecular characterization of single, (4‐hydroxy‐3‐nitrophenyl)acetyl (NP)‐specific, IgG1+ B cells from antibody‐secreting and memory B cell pathways in the C57BL/6 immune response to NP
Authors: Lalor Paul A. , Nossal Gustav J. V. , Sanderson Ralph D. , McHeyzer‐Williams Michael G. 
Published: March 2007

AbstractWe have used multiparameter flow cytometry to identify a population of IgG1+ IgM− antigen‐specific B cells which emerges in spleens of C57BL/6 mice following immunization with the hapten, (4‐hydroxy‐3‐nitrophenyl)acetyl (NP). Characterization of the specificities of IgG1 antibodies produced by single, sorted IgG1+ NP+ cells in both Elispot assays and in microcultures containing lipo‐polysaccharide, interleukin (IL)‐2, IL‐4 and IL‐5 indicates that the splenic IgG1+ NP+ B cell population includes both IgG1 anti‐NP antibody‐secreting cells and non‐secreting, IgG1+ memory B cells. Each functionally discrete population of IgG1+ B cells expresses a distinctive surface phenotype defined by a wide range of B cell markers. In particular, antibody‐secreting, IgG1+ cells were uniquely identified by co‐expression of the matrix receptor, syndecan. The NP‐specific B cell population emerging in the day 7 primary response was assessed for clonotypic diversity by amplification and direct sequencing of the rearranged V186.2 heavy chain variable region gene expressed by single, ex vivo IgG1+ NP+ λ+ B cells. Memory B cell clones, distinguished by junctional diversity, carried either no mutation or a single mutation within rearranged V186.2, suggesting isolation of these cells at the onset of the hypermutation mechanism. This novel approach, therefore, allows the direct and unambiguous identification and characterization of individual B cell clonotypes during their initial selection and activation in antibody responses in vivo.
Mechanisms of induction of primary virus‐specific cytotoxic T lymphocyte responses
Authors: De Bruijn Marloes L. H. , Nieland John D. , Schumacher Ton N. M. , Ploegh Hidde L. , Martin Kast W. , Melief Cornelis J. M. 
Published: March 2007

AbstractWe have investigated the ability of various antigen‐presenting cell (APC) types to induce primary anti‐viral cytotoxic T lymphocyte (CTL) responses by single in vitro stimulation. Of these APC types, only dendritic cells (DC) and RMA‐S lymphoma cells could induce primary CTL responses, but by divergent mechanisms. DC were capable of generating primary virus‐specific CTL, either by presenting viral peptide or processed infectious virus. In contrast, RMA‐S cells could not present endogenous antigen, e. g. after virus infection, but this cell line very efficiently presented exogenous viral peptides to induce primary virus‐specific CTL in vitro. Spleen cells, lipopolysaccharide‐induced B cell blasts or the non‐mutated RMA cells did not have the ability to trigger unprimed T cells by single in vitro stimulation. We have investigated several characteristics important for primary CTL response induction by DC and RMA‐S cells (summarized in Fig. 6). Primary CTL response induction by DC or RMA‐S cells was blocked by anti‐LFA‐1 or anti‐CD8 monoclonal antibodies (mAb). DC rapidly aggregated with unprimed T cells, which was independent of LFA‐1 and CD8 molecules. RMA‐S cells did not form conjugates with unprimed T cells. Despite their abundant major histocompatibility complex (MHC) class I cell‐surface expression, DC did not bind much exogenously added viral peptide. In contrast, the MHC class I molecules on RMA‐S cells bound a large quantity of exogenously administered peptide. Powerful adhesion by DC and high expression of relevant MHC/peptide complexes on RMA‐S cells are important features in the initial contact with unprimed T lymphocytes. In a later stage of contact, both DC and RMA‐S cells activate LFA‐1 (and CD8) molecules at the T cell surface to strengthen and maintain the contact between T cell and APC.
Human neutrophils release their major membrane sialoprotein, leukosialin (CD43), during cell activation
Authors: Rieu Philippe , Porteu Françoise , Bessou Gilles , Lesavre Philippe , Halbwachs‐Mecarelli Lise 
Published: March 2007

AbstractLeukosialin (CD43) is a sialic acid‐rich molecule with a relative molecular mass (Mr) of 140 000 highly represented on polymorphonuclear neutrophils (PMN) and on most leukocytes. One of its functions may be to prevent nonspecific cell‐to‐cell interactions through negative charge repulsions. As tested by immunofluorescence, neutrophil CD43 membrane expression was shown to decrease by up to 80% upon cell activation by phorbol myristate acetate (10 ng/ml) or by N‐formyl‐L‐methionyl‐L‐leucyl‐L‐phenylalanine (FMLP; 10−6 M) in the presence of cytochalasin B. The kinetic of this decrease paralleled that of CD11b up‐regulation. FMLP alone, tumor necrosis factor (TNF‐α), lipopolysaccharide and granulocyte macrophage colony‐stimulating factor had moderate or insignificant effects, while inducing striking CD11b up‐regulation. Cell priming with TNF‐α followed by FMLP stimulation resulted in up to 40% decrease of CD43 expression. Anti‐CD43 mAb immunoprecipitated three fragments of Mr 130 000, 49000 and 34000 from the cell‐free supernatant of activated neutrophils, suggesting that CD43 is released from the membrane by proteolysis. Indeed, the decrease in CD43 expression was inhibited by phenylmethanesulfonylfluoride (PMSF). Homotypic aggregation of activated PMN was also inhibited by PMSF and could result, at least in part, from the shedding of CD43. The shedding of such a strongly anionic and major membrane protein should drastically modify PMN surface charge and may allow previously hindered interactions by exposing new adhesion molecules.
CD45RA −RO+ subset is the major population of dividing thymocytes in the human
Authors: Okumura Meinoshin , Fujii Yoshitaka , Inada Keiji , Nakahara Kazuya , Matsuda Hikaru 
Published: March 2007

AbstractCD45, or leukocyte common antigen, is expressed in different isoforms on different subsets of thymocytes, suggesting its involvement in the process of T cell development in the thymus. We report studies on CD45 isoform expression on human thymocytes at various stages of development using three‐color flow cytometric analysis and cell cycle analysis. Among CD45RO+ cells 18.4% were in S+G2/M phase and represented more than 80% of the dividing cells in the thymus. Among the CD45RO− cells 10.9% were also in cell cycle. Because the CD45RO+ population is almost exclusively CD45RA−, the CD45RA−RO+ subset constitutes the major portion of dividing cells in the thymus. Both the CD1high and the CD3− populations were actively cycling. However, the former was almost 100% and the latter only 50% CD45RA−RO+. Dividing CD45RA−RO+ cells contain, therefore, many cells that have not yet expressed the CD3/T cell receptor complex and presumably have not yet undergone selective procedures. These results are hard to reconcile with the previously presented hypothesis that CD45RO represents a marker for cells that are destined to die in the thymus. Instead, these results suggest an alternative possibility that CD45RO+ cells may contain cells that can mature and, thus, also constitute the thymic generative lineage.
Afferent lymph veiled cells prime CD4+ T cell responses in vivo
Authors: McKeever Declan J. , Awino Elias , Morrison W. Ivan 
Published: March 2007

AbstractThe interdigitating cell (IDC) population of the lymph node paracortex is believed to be responsible for the induction of CD4+ T cell responses to soluble antigens. We have examined the role of afferent lymph veiled cells (ALVC), the putative precursors of IDC, in the induction of primary bovine CD4+ T cell responses in vivo. ALVC prepared from lymph draining an antigen inoculation site stimulated maximal responses in antigen‐specific T cell clones as soon as 30 min after inoculation. In addition, antigen‐pulsed ALVC were shown to induce primary antigen‐specific T cell responses when administered in vivo. Observed influences of fixation and the addition of chloroquine or class II major histocompatibility complex‐specific monoclonal antibodies on presenting function confirmed that ALVC process and present antigens using the endosomal pathway. We conclude that ALVC rapidly internalize antigens deposited in the periphery, and process them for presentation to naive T cells in the draining lymph node. Their function is, therefore, likely to be an important factor in the induction of primary T cell responses to soluble antigens in vivo.
Functional characterization of a novel anti‐B7 monoclonal antibody
Authors: de Boer Mark , Parren Paul , Dove Jeffrey , Ossendorp Ferry , van der Horst Gerda , Reeder John 
Published: March 2007

AbstractFor optimal activation of T cells, binding of their T cell receptor to antigenic peptides in the context of major histocompatibility complex molecules on antigen‐presenting cells (APC) is not sufficient. Accessory signals, provided by accessory cells, are needed to induce proliferation and clonal expansion of normal T cells. It has been shown previously that the B7 molecule, present on the cell surface of activated APC, can provide the second signal by binding to the CD28 molecule on T cells. Here we describe a novel anti‐B7 (mAb), B7‐24. This mAb binds to a functionally important epitope of the B7 molecule. Fab fragments of B7‐24 can almost completely block anti‐CD3‐induced, B7‐dependent T cell proliferation when tested in a model system where purified T cells are co‐cultured with 3T6 cells expressing the human FcγRII and human B7, in the presence of anti‐CD3 mAb. In contrast, mAb B7‐24 is not able to inhibit T cell proliferation in primary mixed lymphocyte reactions where purified T cells are co‐cultured with Epstein‐Barr virus‐transformed B cells. These findings suggest that other cell surface molecules allow for maximal proliferation of T cells in mixed lymphocyte reactions, even when the interaction between B7 and CD28 is blocked by B7‐24.
Rescue from anti‐IgM‐induced programmed cell death by the B cell surface proteins CD20 and CD40
Authors: Valentine Mary A. , Licciardi Karen A. 
Published: March 2007

AbstractProgrammed cell death (PCD), or apoptosis, is characterized by several morphologic alterations and eventual cleavage of nuclear DNA into oligonucleosome‐length fragments. We defined a human B cell line, Ramos, that responds with PCD following ligation of surface IgM. Of the DNA in Ramos cells 3%–10% was fragmented as early as 4 h after IgM ligation. Propidium iodide staining demonstrated that 20%–40% of Ramos cells became apoptotic by 18 h and further established that cells transiting into the S phase of the cell cycle were susceptible to PCD. Addition of several agents to the Ramos cells abrogated anti‐IgM‐induced PCD, including the phorbol 12‐myristate 13‐acetate (PMA). In contrast to the effect of PMA, the 4αPMA isomer of PMA neither activated protein kinase C (PKC) nor rescued the cells from anti‐IgM‐induced PCD, confirming a role for PKC in negating apoptosis. To explore the effect of physiologic signals on anti‐IgM‐induced PCD, antibodies against the CD20 or CD40 molecules were added in concert with anti‐IgM. Both CD20 and CD40 synergize with anti‐IgM to augment proliferation but neither molecule activates PKC in Ramos cells. Both anti‐CD20 and anti‐CD40 reduced the number of cells undergoing anti‐IgM‐induced PCD. Unlike the effect of anti‐CD40, addition of anti‐CD20 to anti‐IgM‐stimulated cells negated PCD only in a subset of cells. Maximal rescue occurred following the addition of anti‐CD40 and occurred by 4 h and at least up to 20 h of culture. These data show that (a) PCD can be initiated in B cells entering the S phase of the cell cycle, (b) PCD can be triggered by engagement of surface IgM in the absence of ancillary signals or PKC activation, and (c) rescue from PCD can occur by several mechanisms, either PKC dependent or PKC independent.
Immunoglobulin x light chain germ‐line transcripts in human precursor B lymphocytes
Authors: Thompson Allan , Timmers Erik , Kenter Marcel J. H. , Kraakman Margriet E. M. , Hendriks Rudolf W. , Schuurman Ruud K. B. 
Published: March 2007

AbstractB lymphoblastoid cell lines (BLCL), established from bone marrow and peripheral blood mononuclear cells from two severe combined immunodeficiency (SCID) patients, manifested a complete absence of genomic rearrangements of the immunoglobulin (Ig) heavy (H) and light (L) chain loci. The BLCL contained germ‐line transcripts of the Ig x region locus of approximately 1.2 kilobases (kb). By cDNA cloning and sequence analysis the transcripts were shown to consist of a Cx segment, a Jx1 gene segment, 160 base pairs (bp) of Jx1 5′ intervening sequence, containing the heptamer/nonamer recombination recognition sequences and at the 5′ end a 523‐bp segment designated human x°, The first 206 bp of this 5′ segment were homologous to the reported murine x° region. Genomic restriction mapping and DNA sequence analysis demonstrated that the human x° segment is located approximately 4 kb upstream of Jx1. The x° segment contains a putative promoter region with an OCT2 binding site, and has a splice donor site to accomplish splicing to an acceptor site 160 bp upstream of Jx1. Expression of the x° gene segment was found in BLCL derived from normal fetal bone marrow, in which both Ig x loci were in the germ‐line configuration. These findings indicate that the described transcripts are not only present in SCID, but also in normal developing pre‐B lymphocytes. The expression of germ‐line Ig x L chain transcripts may be associated with the locus becoming accessible to gene rearrangement.
Peritoneal exudate lymphocyte and mixed lymphocyte culture hybridomas are cytolytic in the absence of cytotoxic cell proteinases and perforin
Authors: Helgason Cheryl D. , Prendergast John A. , Berke Gideon , Bleackley R. Chris 
Published: March 2007

AbstractWe have utilized the sensitive polymerase chain reaction (PCR) to determine whether cytotoxic T lymphocyte (CTL) hybridomas generated from peritoneal exudate lymphocytes (PEL) and mixed lymphocyte cultures (MLC) express transcripts for perforin and the cytotoxic cell proteinases CCP1 to CCP5. We could readily detect less than one transcript per cell using this methodology. Cytolytic activity could be induced to varying levels in four of the five hybridoma clones tested. With the exception of low level CCP2 expression in the MLC hybridoma MD45 following antigen stimulation, all of the hybridomas could be stimulated to function as potent cytolytic cells in the complete absence of perforin or CCP transcripts. PCR analysis utilizing actin primers indicated that all samples contained material which could be reverse transcribed and PCR‐amplified. These results support the argument that populations of lymphocytes do exist that are capable of target cell lysis by an alternative mechanism not involving perforin and CCP.
Development of human Th1 and Th2 cytokine responses: The cytokine production profile of T cells is dictated by the primary in vitro stimulus
Authors: van der Pouw‐Kraan Tineke , de Jong Rolien , Aarden Lucien 
Published: March 2007

AbstractRegulation of interleukin (IL)‐4 production, but not IL‐2 production, was found to be quite different in either freshly isolated T cells or T cell clones. Both fresh T cells and T helper 2‐like clones produced IL‐4 when stimulated with anti‐CD2 in combination with anti‐CD28. However, whereas T cell clones showed enhanced IL‐4 production when phorbol 12‐myristate 13‐acetate (PMA) was used in addition to anti‐CD2 and anti‐CD28, IL‐4 production by fresh T cells was inhibited by the presence of PMA. Prestimulation of fresh T cells led to the following observations: (a) activation in the absence of PMA led to a reversal of the PMA effect and (b) within 2 days these cells resembled T cell clones in that IL‐4 production was no longer inhibited by PMA. When prestimulation was carried out in the presence of PMA, the inhibition of IL‐4 production seemed irreversible. Removal of PMA after 3 days did not lead to renewed capability of IL‐4 production, whereas IL‐2 production was unimpaired. Our data show that the capacity of cultured T cells to produce IL‐4 is determined and fixed during the first 2‐3 days of stimulation.
Localization of self antigen: implications for antigen presentation and induction of tolerance
Authors: Stockinger Brigitta , Gran Catriona F. , Hausmann Barbara 
Published: March 2007

AbstractThe fifth component of complement (C5) is a self antigen expressed in serum of normal mice at a concentration of about 50 μg/ml. We have previously shown that C5 is constitutively processed and presented by antigen‐presenting cells (APC) in normal mice to induce and maintain complete tolerance in major histocompatibility complex (MHC) class II‐restricted T cells. This report addresses the question of whether C5 presentation involves exogenous antigen which has been internalized for processing or whether intracellular, biosynthesized C5 is being presented with MHC class II. Macrophages were found to synthesize, but not secrete C5 in bone marrow chimeras made from irradiated C5‐deficient [C5(−)] hosts reconstituted with C5‐sufficient [C5(+)] bone marrow [C5(+) ← C5(−)]. In these mice, macrophages are the only source of C5. [C5(+) ← C5(−)] chimeras are not tolerant of C5 and generate C5‐specific T and B cell responses upon immunization indistinguishable from those of C5(‐) mice. Macrophages from [C5(+) ← C5(‐)] chimeras are unable to activate C5‐specific T cell hybrids in vitro unlike macrophages from a C5(−) strain that has matured in a C5‐expressing environment [C5(−) ← C5(+) chimeras]. This shows that under physiological conditions in vivo intracellular C5 does not get access to the class II presentation pathway and thus, does not induce tolerance in class II‐restricted T cells.