bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serial killing by cytotoxic T lymphocytes: T cell receptor triggers degranulation, re‐filling of the lytic granules and secretion of lytic proteins via a non‐granule pathway
Authors: Isaaz Sylvie , Baetz Kristin , Olsen Kristin , Podack Eckhard , Griffiths Gillian M. 
Published: March 2007

AbstractCD8+ cytotoxic T lymphocyte (CTL) clones begin to synthesize the lytic proteins granzyme A, granzyme B and perforin after stimulation with allogeneic target cells. The lytic proteins are stored in the secretory granules which are released after cross‐linking of the T cell receptor (TcR) upon target cell recognition. During lytic granule biogenesis granzyme A protein synthesis can be detected between 2 and 10 days after allogeneic stimulation of the CTL. Although granzyme A is stored in the lytic granules over this period, the majority of granzyme A synthesized is secreted directly from the CTL.TcR triggering of degranulation also results in new synthesis of the lytic proteins, which can be inhibited by cycloheximide (CHX). Some of the newly synthesized lytic proteins can be stored in the cell and refill the granules. But up to one third of granzymes A and B can be secreted directly from the CTL via the constitutive secretory pathway as shown by granzyme A enzymatic activity and immunoblots of secreted granzyme B, where one third of the protein fails to acquire the granule targeting signal. Perforin is also secreted via the constitutive pathway, both from the natural killer cell line, YT, and from CTL clones after TcR cross‐linking. Constitutive secretion of the lytic proteins can be blocked by both CHX and brefeldin A (BFA). While BFA does not affect the directional killing of recognized targets, it abrogates bystander killing, indicating that bystander killing arises from newly synthesized lytic proteins delivered via a non‐granule route.These results demonstrate that the perforin/granzyme‐mediated lytic pathway can be maintained while CTL kill multiple targets. We show that CTL not only re‐fill their granules during killing, but also secrete lytic proteins via a non‐granule‐mediated pathway.
Expression and tissue localization of donor‐specific complement C3 synthesized in human renal allografts
Authors: Andrews Peter A. , Finn Jacqueline E. , Lloyd Clare M. , Zhou Wuding , Mathieson Peter W. , Sacks Steven H. 
Published: March 2007

AbstractRecent evidence suggests that the third component of complement, C3, is synthesized in renal tissue, and that increased C3 synthesis occurs in allograft rejection and immune complex‐mediated nephritis. However, it is unclear whether intrinsic renal cells or migratory cells in the inflammatory infiltrate, possibly of recipient bone marrow origin, are the source of the C3 detected. This was investigated by determining the C3 allotypes of mRNA and protein produced by transplanted human kidney. Twenty donor‐recipient pairs were examined, of which nine pairs had C3 allotypes that were informatively mismatched at the C3 F/S locus. Reverse transcriptase polymerase chain reaction (RT‐PCR) followed by amplification refractory mutation system analysis showed intracellular donor‐specific mRNA expression in six of these nine cases, at up to 61 days post‐transplantation. Nested PCR reactions and the size of PCR products excluded contamination by genomic DNA. Allotype‐specific staining of frozen sections of renal cortex demonstrated donor‐derived C3 protein in both glomeruli and tubules of all biopsies examined, in a predominantly tubular distribution. These results imply that at least some of the pro‐inflammatory effects of complement arise from intrinsic tissue synthesis of donor C3, and that this may represent a previously unrecognized source of tissue injury. The occurrence of local synthesis of C3 of donor allotype may have functional implications related to C3 allotype, and may also be relevant to strategies to inhibit intrarenal complement‐mediated injury.
The protein defective in X‐linked agammaglobulinemia, Bruton's tyrosine kinase, shows increased autophosphorylation activity in vitro when isolated from cells in which the B cell receptor has been cross‐linked
Authors: Hinshelwood Steve , Lovering Ruth C. , Genevier Helen C. , Levinsky Roland J. , Kinnon Christine 
Published: March 2007

AbstractX‐linked agammaglobulinemia is a primary inherited immunodeficiency resulting in a lack of or dramatic reduction in the number of mature B lymphocytes and, thus, greatly reduced levels of serum immunoglobulin. The defect results from mutations in the gene for Bruton's tyrosine kinase (Btk). Using rabbit antisera generated against Btk, we have demonstrated an increase in the level of in vitro kinase activity present in anti‐Btk immunoprecipitates from B cells following stimulation with anti‐immunoglobulin antibody. This increase in immune complex kinase activity is detectable 1 to 2 min following stimulation and remains elevated for over 30 min. A similar increase was not seen with two late pre‐B cell lines investigated in the same way. This stimulation of activity may suggest a role for Btk in signalling through the B cell receptor or associated proteins, in mature B cells.
Depletion of CD8+ T cells suppresses the development of experimental autoimmune myasthenia gravis in Lewis rats
Authors: Zhang Guang‐Xian , Ma Cun‐Gen , Xiao Bao‐Guo , Bakhiet Moiz , Link Hans , Olsson Tomas 
Published: March 2007

AbstractTo understand the role of CD8+ T cells in experimental autoimmune myasthenia gravis (EAMG), CD8+ T cells were depleted by injecting a monoclonal anti‐rat CD8 antibody (OX8) into Lewis rats immunized with Torpedo acetylcholine receptor (AChR) in complete Freund's adjuvant (CFA). CD8‐depleted EAMG rats showed strikingly less muscle weakness and lower anti‐AChR IgG antibody levels compared to Hy2‐15‐injected control EAMG rats. Moreover, the numbers of AChR‐specific IgG antibody‐secreting cells, AChR‐reactive interferony‐γ‐secreting T helper type 1‐like cells and lymphocyte proliferation to AChR were lower in the CD8‐depleted group than in control EAMG rats. These differences were significant among mononuclear cells from inguinal and popliteal lymph nodes, mesenteric lymph nodes and spleen, but not from thymus when examined 3, 5 and 7 weeks post‐immunization. We suggest that CD8+ T cells are involved in the induction and persistance of EAMG by directly or indirectly affecting AChR‐reactive T cells and anti‐AChR IgG antibody‐secreting cells.
Substitutions at the Glu62 residue of human interleukin‐2 differentially affect its binding to the α chain and the βγ complex of the interleukin‐2 receptor
Authors: Wang Zhiyong , Zheng Zhongcheng , Sun Lanyin , Liu Xinyuan 
Published: March 2007

AbstractHuman interleukin‐2 (IL‐2) α helix B is more conserved than the whole molecule, but has been less studied than other α helices of IL‐2. Using site‐directed mutagenesis, several IL‐2 mutants in this helix were obtained. We found that the IL‐2 mutant containing Leu at position 62 (Leu62‐IL‐2) loses its ability to bind IL‐2 receptor subunit α (IL‐2Rα), but retains binding affinity to IL‐2R subunit βγ as well as some bioactivity; nevertheless, another substitution at the same residue, Arg62 IL‐2, loses its binding ability to both IL‐2Rα and IL‐2Rβγ, and can no longer stimulate IL‐2‐dependent cell growth, showing that Glu62 not only takes part in IL‐2Rα binding, but can also affect IL‐2 binding to IL‐2Rβγ. In this regard, Glu62 may be a key site in the IL‐2/IL‐2Rα interaction, and can facilitate IL‐2R ternary‐complex formation, leading to IL‐2Rα‐mediated, IL‐2‐stimulated signal transduction.
Human T helper cells specific for HIV reverse transcriptase: possible role in intrastructural help for HIV envelope‐specific antibodies
Authors: Manca Fabrizio , Fenoglio Daniela , Valle Maria T. , Li Pira Giuseppina , Kunkl Annalisa , Balderas Robert S. , Baccala Roberto G. , Kono Dwight H. , Ferraris Anna , Saverino Daniele , Lancia Flavia , Lozzi Luisa , Theofilopoulos Argyrios N. 
Published: March 2007

AbstractCooperation between B cells specific for an antigen exposed on a viral structure and T helper (Th) cells specific for an internal antigen, as demonstrated with influenza, hepatitis B and rabies viruses, has been termed intrastructural help. Th cells specific for internal proteins of HIV, which are much less mutated than its exposed antigens, may be valuable in vaccine design against this virus. We investigated the human Th repertoire specific for the core HIV antigen reverse transcriptase (p66), and determined whether these cells could be candidate intrastructural T helpers. CD4+ T lines and clones were generated from non‐immune individuals by stimulation with p66‐pulsed antigen‐presenting cells (APC). Specific lines were obtained with p66 from 19 out of 21 (90%) of these individuals, vs. 7 out of 29 (24%) with gp120. Diverse epitopes were recognized by different individuals, and various Vβ genes were used by these clones. Clones using the same Vβ genes were of diverse origin, according to VDJ region sequence. Of these lines 45% responded to p66 in the context of HIV virions. Moreover, p66‐specific clones could respond to APC that had internalized HIV complexed with envelope‐specific monoclonal antibodies, suggesting that p66‐specific Th cells may participate in intrastructural help. These studies indicate that p66‐specific Th cells are detectable in vitro in most naive individuals and exhibit clonal heterogeneity, and that the majority recognize an HIV conserved antigen. They respond to p66 following processing of whole virions and are clearly candidates for intrastructural help. If confirmed in vivo, p66 should be included among vaccine candidates investigated to optimize the anti‐HIV Th response.
Signaling via major histocompatibility complex class II molecules and antigen receptors enhances the B cell response to gp39/CD40 ligand
Authors: Bishop Gail A. , Warren Wendy D. , Berton Michael T. 
Published: March 2007

AbstractActivated T cells induce proliferation and differentiation of resting B cells in vitro through their CD40 molecules and lymphokine receptors. However, despite constitutive B cell expression of CD40 and lymphokine receptors, widespread nonspecific polyclonal B cell activation by activated T cells is seldom observed in vivo. The present study was designed to test the hypothesis that signals delivered via the B cell antigen (Ag) receptor (membrane immunoglobulin, mIg) and major histocompatibility complex (MHC) class II molecules enhance B cell responsiveness to CD40‐mediated signals, providing specificity to the Ag‐nonspecific, MHC‐unrestricted CD40 signal. To test this hypothesis, both an Ag‐specific mouse B cell clone CH12.LX, and freshly isolated resting splenic B cells were cultured with either soluble or membrane‐bound forms of the T cell ligand for CD40 (CD40L), in the presence or absence of additional signals provided by Ag or anti‐IgM, interleukin‐4, and class II‐specific monoclonal antibody (mAb). Differentiation of CH12.LX cells and proliferation of splenic B cells in response to both forms of CD40L was greatly enhanced by exposure to mIg‐mediated signals, with greatest enhancement seen when cells were cultured with Ag prior to receiving other signals. Response to CD40L was further enhanced by concurrent culture with class II‐specific, but not class I‐specific mAb. Enhancement was greatest at limiting concentrations of CD40L. The ability of class II MHC‐mediated signals to enhance Ag‐specific B cell responsiveness to CD40‐mediated signaling may selectively promote the activation of B cell clones capable of cognate interactions with helper T cells.
Modulation of CD4 lateral interaction with lymphocyte surface molecules induced by HIV‐1 gp120
Authors: Dianzani Umberto , Bragardo Manuela , Buonfiglio Donatella , Redoglia Valter , Funaro Ada , Portoles Pilar , Rojo José , Malavasi Fabio , Pileri Alessandro 
Published: March 2007

AbstractCD4, a lymphocyte surface glycoprotein, serves as co‐receptor for antigen with the T cell receptor (TCR). It is also the lymphocyte receptor for HIV by binding the gp120 viral envelope protein. Interaction of gp120 with CD4 is crucial for viral infection, but is not sufficient to allow viral entry into cells. Recombinant gp120 alters CD4+ T cell responsiveness to activation stimuli. To express its co‐receptor function fully, CD4 must be laterally associated with the TCR and CD45 to form multi‐receptor complexes competent to transduce potent activation signals. Here, we examine the possibility that gp120/CD4 binding alters lateral associations of CD4 with other lymphocyte surface molecules, and that assembly of abnormal multi‐molecular complexes is involved in the gp120‐induced CD4+ T cell dysfunction and in viral entry. In the absence of gp120, CD4 displayed high association with CD3, CD5, CD45RC, CD25, CD28, CD44, and CD53; weak association with CD2, CD38, CD45RB, CD62L, and CD26; and no association with CD45RA, CD45RO, CD11b, CD11a, CD54, CD7, CD48, CD98, CD59, CD55, HLA class I and class II molecules. Treatment with gp120 significantly increased CD4 association with CD3, CD45RA, CD45RB, CD59, CD38, CD26, and HLA class I, and decreased that with CD45RC. Specificity of these results were assessed at various levels. First, gp120 did not influence lateral associations displayed by other molecules, such as HLA class II. Second, the Leu3 mAb, which binds CD4 on a site overlapping the gp120 binding site, did not elicit the same CD4 lateral associations as gp120, and finally, a direct gp120/CD4 interaction was needed to induce the lateral associations, as shown by the observation that blocking the gp120/CD4 binding by the Leu3 mAb inhibited the gp120‐induced associations. These results can be interpreted in several ways. gp120/CD4 interaction could trigger an inside‐out signal responsible for the associations, or gp120 could induce steric modifications of CD4 that increase its affinity for the associating molecules. Alternatively, these molecules may interact directly with gp120, bridging them with CD4. It is also possible that the associations may be mediated by additional components, interacting with both gp120 and the associating surface molecule. The last hypothesis is likely for CD59, whose gp120‐induced association with CD4 required the presence of serum in the co‐capping assay. Since both CD59 and gp120 bind complement, the observed association could be mediated by complement components.
Down‐regulation of class II major histocompatibility complex molecules on antigen presenting cells after interaction with helper T cells
Authors: Vidović Damir , Falcioni Fiorenza , Bolin David R. , Nagy Zoltan A. 
Published: March 2007

AbstractThe recognition of antigenic peptides by CD4+ helper T cells is demonstrated here to result in a dramatic (up to 90%) decrease in expression of major histocompatibility complex (MHC) class II molecules on the surface of antigen‐presenting cells (APC). The reduction is selective to the class II isotype presenting the antigen, but if affects both allelic forms of the same isotype in heterozygous APC. The observed MHC down‐regulation requires a specific T cell receptor‐peptide‐class II interaction, a direct contact between T cell and APC, and the involvement of CD2 molecules. These findings have important implications for the regulation of immune response, self tolerance, and autoimmunity.
Developmentally regulated expression of P‐glycoprotein (multidrug resistance) activity in mouse thymocytes
Authors: MacDonald H. Robson , Bommhardt Ursula , Cerottini Jean‐Charles 
Published: March 2007

AbstractP‐glycoprotein (P‐gly) is the transmembrane efflux pump responsible for multidrug resistance in tumor cells. The activity of P‐gly in mature peripheral lymphocytes is lineage specific, with CD8+ T cells and natural killer (NK) cells expressing high levels as compared to CD4+ T cells and B cells. We have now investigated P‐gly activity in immature and mature subsets of mouse thymocytes. Our data indicate that P‐gly activity is undetectable in immature CD4−8− and CD4+8+ thymocyte subsets. Among mature thymocytes, P‐gly activity is absent in the CD4+ subset but present in the more mature (HSAlow) fraction of CD8+ cells. Furthermore, while thymic CD4−8− T cell receptor (TCR) γδ cells have little P‐gly activity, a minor subset of CD4−8− or CD4+ TCR αβ+ thymocytes bearing the NK1.1 surface marker expresses high levels of P‐gly activity. Collectively, our results indicate that P‐gly activity arises late during thymus development and is expressed in a lineage‐specific fashion.
Non‐exclusive Fas control and age dependence of viral superantigen‐induced clonal deletion in lupus‐prone mice
Authors: Papiernik Martine , Pontoux Christiane , Golstein Pierre 
Published: March 2007

AbstractTo investigate the role of Fas in the induction of tolerance by viral superantigen (SAG), we infected MRL‐+/+ and MRL‐lpr (Fas mutant) mice with mouse mammary tumor virus (MMTV) (SW), a virus encoding an SAG with the same specificity as endogenous Mtv‐7‐SAG. In normal mice, this infection has two distinct consequences on specific Vβ6+CD4+ T cells, consisting of activation followed by clonal deletion. MMTV (SW)‐SAG‐induced activation in vivo was identical in MRL‐+/+ and MRL‐lpr mice. In contrast, clonal deletion showed age‐dependent impairment. Early infection (5 weeks) led to identical clonal deletion of specific T cells in blood lymphocytes from MRL‐+/+ and MRL‐lpr mice, although clonal deletion was slightly impaired in the MRL‐lpr lymph nodes. Late infection (10 weeks) of MRL‐lpr mice led to markedly delayed and reduced clonal deletion. Vβ6+CD4+ T cells which escaped clonal deletion in aging MRL‐lpr mice were not anergized by interaction with SAG. These results show that peripheral clonal deletion induced by viral SAG in adult mice is controlled by Fas, but not exclusively so.
Induction of CTL in vivo by major histocompatibility complex class I‐peptide complexes covalently associated on the cell surface
Authors: Anjuère Fabienne , Horvath Clotilde , Cerottini Jean‐Charles , Luescher Immanuel F. 
Published: March 2007

AbstractThe identification of endogenously produced antigenic peptides presented by MHC class I molecules has opened the way to peptide‐based strategies for CTL induction in vivo. Here we demonstrate that the induction in vivo of CTL directed against naturally processed antigens can be triggered by injection of syngeneic cells expressing covalent major histocompatibility complex class I‐peptide complexes. In the model system used, the induction of HLA‐Cw3 specific cytotoxic T lymphocytes (CTL) in mice by cell surface‐associated, covalent H‐2Kd (Kd)‐Cw3 peptide complexes was investigated. The Kd‐restricted Cw3 peptide 170–179 (RYLKNGKETL), which mimics the major natural epitope recognized by Cw3‐specific CTL in H‐2d mice, was converted to a photoreactive derivative by replacing Arg‐170 with N‐β‐(4‐azidosalicyloyl)‐L‐2,3‐diaminopropionic acid. This peptide derivative was equivalent to the parental Cw3 peptide in terms of binding to Kd molecules and recognition by Cw3‐specific CTL clones and could be cross‐linked efficiently and selectively to Kd molecules on the surface of Con A‐stimulated spleen cells from H‐2d mice. Photocross‐linking prevented the rapid dissociation of Kd‐peptide derivative complexes that takes place under physiological conditions. Cultures of spleen cells or peritoneal exudate cells from mice inoculated i.p. with peptide‐pulsed and photocross‐linked cells developed a strong CTL response following antigenic stimulation in vitro. The cultured cells efficiently lysed not only target cells sensitized with the Cw3 170–179 peptide but also target cells transfected with the Cw3 gene. Moreover, their TCR preferentially expressed Vβ10 and JαpHDS58 segments as well as conserved junctional sequences, as has been observed previously in Cw3‐specific CTL responses. In contrast, no Cw3‐specific CTL response could be obtained in cultures derived from mice injected with Con A‐stimulated spleen cells pulsed with the peptide derivative without photocross‐linking.
Germ‐line transcription of the T cell receptor δ gene in mouse hematopoietic cell lines
Authors: Shimamura Michio , Ohta Sachiko 
Published: March 2007

AbstractT cell receptor (TCR) genes are initially activated in hematopoietic stem cells that have been committed to the T cell lineage during ontogeny. We have established cell lines derived from hematopoietic organs which express truncated TCR δ mRNA (1.3 kbp). In this study, cDNA clones of this mRNA were analyzed to characterize TCR δ gene activation in early T cell development. Transcription started from an intron between Dδ2 and Jδ1, 72 bp upstream from Jδ1, and continued to Jδ1 and Cδ exons, which were directly spliced to Jδ1. Thus, the truncated mRNA expressed by the cell lines was determined to be a germ‐line transcript. The promoter activity of the DNA fragment between Dδ2 and Jδ was assessed by its ability to drive the transcription of a reporter gene linked to it in the cell line expressing the TCR δ germ‐line transcript. TCR δ germ‐line transcription was found not only in these cell lines but also in fetal liver and thymus cells. These findings indicate that the TCR δ germ‐line transcription is a naturally occurring event in developing T cells. The significance of germ‐line transcription of TCR δ genes is unknown, but it may be an event that follows T‐lineage commitment or, at least, may be closely associated with this commitment.
Interleukin‐4 and ‐10 exacerbate candidiasis in mice
Authors: Tonnetti Laura , Spaccapelo Roberta , Cenci Elio , Mencacci Antonella , Puccetti Paolo , Coffman Robert L. , Bistoni Francesco , Romani Luigina 
Published: March 2007

AbstractNeutralization of endogenous interleukin (IL)‐4 or IL‐10 in mice with Candida albicans infection initiates or accelerates development of a T helper (Th)1‐associated protective response. Here, we report the effect of IL‐4 and IL‐10 administration on the course of systemic or gastrointestinal (GI) candidiasis and on the development of Th immunity using yeast/host combinations that result either in Th1‐associated self‐limiting infection (healer mice) or in Th2‐associated progressive disease (nonhealer mice). Treatment with IL‐4 or IL‐10 greatly exacerbated the course of systemic infection in nonhealer mice and rendered healer mice, inoculated with attenuated yeast cells, susceptible to infection. Under the latter conditions of yeast challenge and IL‐4/IL‐10 administration, the development of a fatal disease was associated with inhibition of IL‐12 production and detection of progressive Th2 cell dominance. In contrast, in healer mice allowed to resolve their infections and to develop long‐lived anti‐candidal resistance, the expression of this acquired resistance was not impaired by IL‐4 and/or IL‐10, as shown by the outcome of reinfection with virulent yeast cells. In the GI model of infection, both IL‐4 and IL‐10 were found to exacerbate the course of infection and to induce the appearance of CD4+ T cells producing high levels of IL‐4 and IL‐10 in Peyer's patches. These findings demonstrate that exogenous IL‐4 and IL‐10 may greatly affect the development of Th responses to C. albicans in vivo, but do not modify the expression of established and predominant Th1 cell reactivity.