bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permissive recognition during positive selection
Authors: Pawlowski Tomasz J. , Singleton Michael D. , Loh Dennis Y. , Berg Rance , Staerz Uwe D. 
Published: March 2007

AbstractIn the periphery αβ T lymphocytes recognize antigens in conjunction with major histocompatibility complex (MHC) molecules. In the thymus immature T cells are positively selected on MHC molecules in the apparent absence of cognate peptides. Thus, at different developmental stages a T cell responds to different epitopes, yet uses the identical αβ T cell antigen receptor (TcR). To explain this paradox it has been hypothesized that during positive selection immature T cells see peptides/ligands unique to the thymus, are selected by specific antagonists related to their cognate peptides, or are driven by lowered affinity thresholds of their TcR. Though different in detail, these theories rely on defined peptides uniquely matched to select certain TcR. However, we find that in a TcR‐transgenic (TcRtrans+) mouse severely limiting the diversity of peptides does not impair positive selection. We show that many unrelated peptides, including some naturally occurring on the cell surface, induce maturation of CD4−CD8+TcRhigh thymocytes. The same peptides when presented in conjunction with the selecting MHC molecule, are not recognized by peripheral T cells expressing the same TcRtrans. Therefore, these findings point to a promiscuous rather than discriminate recognition mode used by immature T cells.
Expression and function of B7‐1 and B7‐2 in hapten‐induced contact sensitivity
Authors: Reiser Hans , Schneeberger Eveline E. 
Published: March 2007

AbstractWe analyzed the expression and function of the co‐stimulatory molecules B7‐1 (CD80) and B7‐2 (CD86) during contact sensitivity reactions induced by the hapten 2,4‐dinitrofluorobenzene (DNFB). In the normal skin, only a few epidermal Langerhans cells or dermal dendritic cells express B7‐2. In contrast, following challenge with DNFB, expression of B7‐2 is up‐regulated in both epidermis and dermis. Importantly, B7‐1 is induced later and at lower levels compared to B7‐2. Intravenous injections of anti‐B7‐2 mAb, but not anti‐B7‐1 mAb partially inhibit the hapten‐induced contact sensitivity reaction. Experiments in which mice are injected differentially with anti‐B7‐2 mAb, either before the afferent or before the efferent phase of the contact sensitivity response, suggest that B7‐2 is important for successful antigen priming.
Inhibition of tumor necrosis factor activity minimizes target organ damage in experimental autoimmune uveoretinitis despite quantitatively normal activated T cell traffic to the retina
Authors: Dick Andrew D. , McMenamin Paul G. , Körner Heinrich , Scallon Bernard J. , Ghrayeb John , Forrester John V. , Sedgwick Jonathon D. 
Published: March 2007

AbstractRecent studies demonstrated that administration of a p55‐tumor necrosis factor (TNF) receptor IgG‐fusion protein (TNFR‐IgG) prevented the clinical onset of experimental autoimmune encephalomyelitis but did not alter the number or tissue distribution of autoantigen‐specific CD4+ effector T cells which trafficked into the central nervous system. To determine whether specific target tissues of autoimmune damage remain intact after TNFR‐IgG treatment despite the presence of inflammatory cells within the tissues, we examined rats with experimental autoimmune uveoretinitis (EAU), as in this model, the main target of autoreactive CD4+ T cells, the retinal rod outer segments (ROS), can be examined readily by light microscopy. As judged by direct ophthalmoscopy, the onset of inflammation in the anterior chamber of the eye in EAU following administration of TNFR‐IgG was delayed by 6 days compared to untreated controls, but the magnitude of the response was only slightly less than controls. Histological examination of the retinae and direct assessment of retinal inflammation revealed a disproportionate sparing of ROS in the TNFR‐IgG‐treated animals despite a level of retinal inflammation not substantially less than controls in which ROS damage was marked. Analysis of retinal leukocytes by immunofluo‐rescence microscopy and flow cytometry indicated that approximately equal numbers of CD4+ αβTCR+ lymphocytes were present in treated and control retinae, more than 30% of CD4+ cells in both experimental groups expressed the CD25 or MRC OX40 activation markers and most cells, which would include the CD4+ T lymphocytes, were activated as evidenced by MHC class II expression. Fewer activated macrophages and granulocytes were present in the treated retinae, possibly reflecting the lower level of tissue damage and subsequent accumulation of these inflammatory cells. The results demonstrate directly that a tissue specifically targeted for autoimmune destruction can be protected despite the influx of fully activated CD4+ T cells.
Fas‐mediated apoptosis is modulated by intracellular glutathione in human T cells
Authors: Chiba Takayuki , Takahashi Shuji , Sato Noriyuki , Ishii Seiichi , Kikuchi Kokichi 
Published: March 2007

AbstractFas antigen is a member of the tumor necrosis factor receptor family that transduces a lethal signal to the Fas‐sensitive cells. We previously established the Fas‐resistant variant cell lines LAC2D1R and JKT2D1R from the parental Fas‐sensitive cell lines, SUPT13 and Jurkat, respectively. Recently, we isolated the Fas‐resistant variant CEM2D1R from CCRF‐CEM. All of the variants were Fas+ but resistant to Fas‐mediated apoptosis. Further biochemical analysis revealed that the intracellular gluthathione (GSH) content of the Fas‐resistant variants was higher than in the original cells. When the Fas‐resistant variants were incubated with buthionine sulfoximine (BSO) or in GSH‐free/cysteine‐free medium to deplete GSH, Fas resistance was reversed. Incubation of the cells with cycloheximide also decreased intracellular GSH and reversed the Fas resistance. Furthermore, incubation of activated peripheral blood lymphocytes with BSO enhanced Fas‐mediated apoptosis. When the Fas‐sensitive cells were incubated with N‐acetylcysteine (NAC), intracellular GSH was increased and Fas‐mediated apoptosis was blocked. In contrast, Fas‐resistant variants, as well as Fas‐sensitive cells pre‐treated with NAC remained susceptible to allogeneic lymphokine‐activated killer cells, most likely due to perforin‐dependent killing. The results suggest that Fas‐mediated apoptosis, but not perforin‐dependent killing, is modulated by intracellular GSH in human T lymphocytes.
CD4‐dependent and ‐independent association of protein tyrosine kinases to the T cell receptor/CD3 complex of CD4+ mouse T lymphocytes
Authors: Criado Gabriel , Feito Maria José , Rojo José M. 
Published: March 2007

AbstractTyrosine phosphorylation of different substrates is the earliest intracellular signal detected after T cell receptor (TcR) ligation. Several tyrosine kinases have been detected associated to the CD3‐TcR complex in stimulated or unstimulated cells, including p56lck, p59fyn and ZAP‐70. We have observed, in one mouse T helper CD4 T cell line, that most TcR‐ or CD3‐associated tyrosine kinase activity comes from CD4:p56lck (Diez‐Orejas, R., Ballester, S., Feito, M. J., Ronda, M., Ojeda, G., Criado, G., Portolées, P. and Rojo, J. M., EMBO J. 1994. 13: 90). To analyze whether this is a major way of tyrosine kinase association to the TcR in normal CD4+ T cells, we examined the nature and mode of association of tyrosine kinases to the TcR complex in normal spleen CD4+ T lymphocytes. Our results show that, in normal CD4+ T lymphocytes, as in CD4+ T cell lines, there is a stable and readily detectable association between CD4: p56lck and the TcR/CD3 complex, as determined by in vitro kinase activity in immunoprecipitates from cell lysates. However, TcR/CD3 complexes from nature CD4+ lymphocytes have detectable amounts of p56lck associated in a CD4‐independent manner, as shown by immunodepletion of the lysates with anti‐CD4 antibodies. In addition, TcR/CD3 also bind p59fyn regardless of the presence of CD4. Conversely, we have observed that CD4 co‐precipitates small quantities of p56fyn in a TcR/CD3‐independent manner. Overall, our data suggest the existence of different possible molecular complexes between TcR/CD3, CD4 and their attending kinases, as well as some quantitative and qualitative differences between CD4+ T cells and CD4+ T cell lines in kinase association to the TcR/CD3 complex.
Signal extinction and T cell repolarization in T helper cell‐antigen‐presenting cell conjugates
Authors: Valitutti Salvatore , Müller Sabina , Dessing Mark , Lanzavecchia Antonio 
Published: March 2007

AbstractWe have previously demonstrated that in T cell‐antigen‐presenting cell (APC) conjugates many T cell receptors (TCR) are serially triggered by a few peptide‐MHC complexes, resulting in sustained signaling. Here, we investigate the mechanisms that determine the duration and extent of signaling. We show that in the course of the T helper cell‐APC interaction, down‐regulation of triggered TCR leads to extinction of signaling. However, T cells that have been activated by a previous encounter with peptide‐pulsed APC and have extinguished signaling can swiftly repolarize towards APC displaying higher antigen concentrations and dedicate their help to these cells. These results demonstrate that TCR down‐regulation allows T cells to calibrate their response and dedicate their help to APC offering the highest stimulus.
Immunity to viruses in B cell‐deficient mice: Influence of antibodies on virus persistence and on T cell memory
Authors: Bründler Marie‐Anne , Aichele Peter , Bachmann Martin , Kitamura Daisuke , Rajewsky Klaus , Zinkernagel Rolf M. 
Published: March 2007

AbstractMice rendered B cell deficient by targeted disruption of the immunoglobulin μ chain gene (IgM−/− mice) were used to analyze the role of antibodies and B cells in viral infections; homozygous IgM−/− mice were bred in a way to avoid transmission of maternal antibodies. After infection with vesicular stomatitis virus (VSV), IgM−/− mice developed paralytic disease and subsequently died, whereas C57BL/6 control mice or IgM−/− mice passively protected with VSV‐neutralizing antibodies survived. Furthermore, IgM−/− mice showed increased natural killer (NK) activity upon exposure to either lymphocytic choriomeningitis virus (LCMV) or to poly(I) · poly(C), while NK activity in untreated IgM−/− mice was within normal ranges. Cytotoxic T cell responses were comparable in IgM−/− and control mice infected either with VSV or with vaccinia virus or with low doses of LCMV (102 infectious focus‐forming units [ifu]). After intracerebral infection with LCMV‐Armstrong, CD8+ T cell‐mediated lethal lymphocytic choriomeningitis developed independently of the presence of B cells and antibodies. After infection with high doses (2 × 106 − 5 × 106 ifu) of LCMV‐WE or LCMV‐Docile, IgM−/− mice exhibited a reduced capacity to control these primary infections and had elevated virus liters for prolonged times (>60 days). Nevertheless, the cytotoxic T cell response against LCMV in the early phase of infection was comparable in IgM−/− and control mice, but disappeared in those IgM−/− mice which had a persistent viral infection. Cytotoxic T cell memory was apparently unimpaired in low‐dose‐primed IgM−/−mice, which were able to control the primary virus infection; both IgM−/− and control mice cleared a high intravenous dose of virus within 2 days after challenge infection. This indicates that an efficient T cell memory against LCMV was established in the absence of B cells.
Transcriptional and translational control of TNF‐α gene expression in human monocytes by major histocompatibility complex class II ligands
Authors: Espel Enric , Garcia‐Sanz Jose A. , Aubert Vincent , Menoud Véronique , Sperisen Peter , Fernández Neus , Spertini François 
Published: March 2007

AbstractWhile non‐stimulated primary human monocytes exhibit very low levels of tumor necrosis factor (TNF)‐α mRNA, direct binding of the staphylococcal exotoxin toxic shock syndrome toxin‐1 (TSST‐1) to major histocompatibility complex (MHC) class II molecules results in a fast (peak 1 h after stimulation), transient induction (sevenfold) of TNF‐α mRNA. This induction correlates with a fourfold increase in transcription rates of the TNF‐α gene, as detected by run‐on assays, and does not require de novo protein synthesis. Mapping of DNase‐I hypersensitive sites (DHS) discloses two constitutive DHS, one located far upstream (within the TNF‐β promoter) and the other centered at −39 ± 40 bp relative to the major TNF‐α transcription start site, suggesting that the TNF‐α gene was transcriptionally competent even prior to MHC class II engagement. Furthermore, stimulation of human monocytes with either TSST‐1 or lipopolysaccharide increases the translational efficiency of TNF‐α mRNA, as shown by a shift in the distribution of this mRNA species in polysome gradients and the translation rates of TNF‐α measured by immunoprecipitation from cells pulsed with [35S] methionine. The increase in translation efficiency of TNF‐α mRNA is independent of the half‐life of TNF‐α transcripts, which under the conditions used is unchanged. Taken together, our data indicate that TNF‐α expression is tightly regulated by MHC class II ligands, both at the transcriptional and translational levels.
Tyrosine kinase‐dependent activation of human NK cell functions upon triggering through CD44 receptor
Authors: Galandrini Ricciarda , Piccoli Mario , Frati Luigi , Santoni Angela 
Published: March 2007

AbstractWe recently showed evidence of CD44‐mediated enhancement of natural killer (NK) cell cytotoxic activity and induction of intracellular Ca2+ flux. In this study, we evaluated whether CD44 plays a stimulatory role in NK cell functions, such as cytokine production and activation antigen expression. Our results indicate that ligation of the CD44 receptor results in the induction of expression of the CD69 surface activation antigen as well as in the enhancement of phorbol ester‐induced TNF‐α secretion. We report also evidence for the coupling of CD44 receptor to a protein tyrosine kinase(s) pathway. CD44 engagement rapidly stimulates the tyrosine phosphorylation of several cellular substrates. Pretreatment of NK cells with the tyrosine kinase inhibitor herbimycin A resulted in marked decrease of CD44‐stimulated phosphorylation, indicating that it activates tyrosine kinase(s). Furthermore, the drug also prevents CD44‐mediated TNF‐α production and CD69 expression. These findings indicate that protein tyrosine phosphorylation is an early and critical event in CD44‐mediated activation of NK cell functions.
Epitope selection in major histocompatibility complex class I‐mediated pathway is affected by the intracellular localization of an antigen
Authors: Yamazaki Hiroko , Tanaka Masato , Nagoya Masako , Fujimaki Haruka , Sato Kazuki , Yago Tadayuki , Nagata Toshi , Minami Mutsuhiko 
Published: March 2007

AbstractWe analyzed the mode of antigen presentation of an endogenous antigen localized in the cytoplasm or in the mitochondria. Pseudomonas aeruginosa PAO leucine‐, isoleucine‐, valine‐binding protein (LIVAT‐BP) encoded by the braC gene was used as a model antigen. Using mouse BALB/3T3 cells, we established two LIVAT‐BP transfectants by transfection of a plasmid harboring the intact braC or braC gene fused with the mitochondrial transport signal derived from the yeast COXIV gene. One of the resulting transfectants, BC‐15, expressed LIVAT‐BP in the cytoplasm, while YZ‐710 cells expressed LIVAT‐BP in the mitochondria. The splenic effector cells derived from BALB/c mice primed with BC‐15 cells exhibited cytotoxic T lymphocyte (CTL) activity against BC‐15 cells, but not against YZ‐710 cells, whereas splenic effector cells primed with YZ‐710 cells exhibited CTL activity against YZ‐710 cells, but not against BC‐15 cells. Neither group of splenic effector cells showed CTL activity against parental BALB/3T3 cells. These CTL belonged to the CD8+ αβ T cell subset. Furthermore, we observed that the CTL activity against BC‐15 cells or YZ‐710 cells was blocked with anti‐H2‐Kd mAb, but not with anti‐H2‐Dd or H2‐Ld mAb. The CTL against BC‐15 or YZ‐710 cells could kill parental BALB/3T3 cells in the presence of peptides produced by alkali lysis of the LIVAT‐BP. suggesting that these CTL indeed recognized the peptide(s) derived from LIVAT‐BP. We determined that the epitope for the CTL against BC‐15 cells was QYGEGIATEV, corresponding to residues 162–171, and that the epitope recognized by the CTL against YZ‐710 cells was GYKLIFRTI, corresponding to residues 123–131 of LIVAT‐BP, respectively. Thus, we show here that epitope selection for MHC class I expression is affected by the intracellular localization of the antigenic protein.
Clonal analysis of immunoglobulin mRNA in rheumatoid arthritis synovium: Characterization of expanded IgG3 populations
Authors: Williams David Gareth , Taylor Peter Charles 
Published: March 2007

AbstractPlasma cells secreting IgG, M, and A abound in the synovium of patients with rheumatoid arthritis, yet their immunoglobulin repertoire and clonal relationship remain to be elucidated. Locally synthesized immunoglobulins probably contribute to the chronic joint inflammatory processes which are characteristic of these patients. To determine whether B lymphocyte proliferation contributes to the synovial plasma cell infiltrate, the clonality of IgG mRNA in individual synovial biopsies from an actively inflamed joint of patients with rheumatoid arthritis was investigated by a combination of cDNA length analysis and DNA sequencing. Particular sizes of immunoglobulin cDNA, detectable in subclasses 1, 3, or 4, were expressed in most synovial biopsies from one patient, suggesting their origin from expanded clones present in each biopsy. To prove a clonal relationship between recurrent cDNA lengths, immunoglobulin cDNA was cloned from three regions of synovium in three patients. The sequence of clones with a recurrent cDNA length was determined. An IgG3 clone found in most synovial biopsies of one patient was encoded by an unmutated copy of the VH1 gene, DP7. In contrast, IgG3 clones encoded by mutated versions of the VH3 gene DP49 or the VH4 gene DP63 were expanded in the other two patients. Different somatic mutants of these clones were isolated from different sites in these patients. The ratio of replacement/silent somatic mutations in these two families of clones suggests that the selective clonal expansion in the synovium of patients with rheumatoid arthritis is due to an antigen‐driven immune response.
Cytotoxic T lymphocyte responses to wild‐type and mutant mouse p53 peptides
Authors: Bertholet Sylvie , Iggo Richard , Corradin Giampietro 
Published: March 2007

AbstractCytotoxic T lymphocytes (CTL) recognize peptides presented at the cell surface in association with major histocompatibility complex (MHC) class I molecules. The finding that peptides binding to MHC class I molecules share common amino acid motifs renders feasible the selection of antigenic peptides by simply scanning protein sequences, and thus, provides the possibility of inducing CTL to pre‐defined specificities. Tumor cells possess antigens known to generate MHC class I‐restricted CD8+ CTL responses. Thus, these antigens represent good targets to induce tumor‐specific immunity. Among these antigens, the p53 tumor suppressor gene product is an attractive candidate for cancer immunotherapy. Mutations in the p53 gene have been found to be very frequently associated with a malignant transformation and often lead to p53 protein overexpression. Thus, we investigated the possibility of inducing CTL to wild‐type or mutant p53 peptides in a BALB/c (H‐2d) mouse model. Peptides possessing the H2‐Kd binding motif were selected and tested for binding to the H‐2Kd molecules in vitro. Synthetic peptides p53122–130 wild‐type or “mutant” (Lys → Glu substitution at position 129) were shown to be the best binder peptides and were tested for their immunogenicity in mice. H‐2Kd‐restricted p53‐specific CD8+ CTL were generated following immunization of mice with either wild‐type (wt) p53122–130 or mutant (mut) p53122–130 (E129) peptides. Only low‐affinity CTL can be obtained by immunization with the wt sequence. In contrast, CTL elicited with the mut peptide recognized the mut sequence at a 10–100‐fold lower concentration. This indicates that CTL elicited with the mut peptide recognized the mut sequence very efficiently, whereas the wt sequence is poorly recognized, if at all. Taken together, these results thus suggest that p53‐specific tumor immunotherapy may be successful only if the mutated protein is taken into consideration.
Diffuse large cell lymphomas are derived from mature B cells carrying V region genes with a high load of somatic mutation and evidence of selection for antibody expression
Authors: Küppers Ralf , Rajewsky Klaus , Hansmann Martin‐Leo 
Published: March 2007

AbstractIn the Revised European American Lymphoma (REAL) classification, several subtypes of high‐grade lymphomas were combined in the entity diffuse large cell lymphoma (DLL). In the present study, a total of 19 cases of DLL (10 cases of centroblastic lymphoma, 5 cases of mediastinal B cell lymphoma, 2 cases of immunoblastic lymphoma, 1 case of T cell‐rich B lymphoma and one case of large cell anaplastic lymphoma) were analyzed for somatically mutated immunoglobulin V region genes. Somatic mutations are acquired in the course of the germinal center (GC) reaction and are thus found in GC B cells and their descendants, i.e. memory B cells. The V gene sequences revealed that the tumor cells of all five subtypes of DLL harbored mutated V region genes and are thus derived from antigen‐experienced (post) GC B cells. This indicates that from the point of view of the stage of development of the tumor precursor, the combination of those five subtypes to one entity, i.e. DLL, seems reasonable. In some cases, an unusually high frequency of somatic mutations was detected. This may indicate that DLL are derived from GC B cells, which, due to transforming events, stayed in the GC for prolonged periods of time, thereby accumulating a high load of somatic mutation. An analysis of the mutation pattern suggests that the tumor clone or its precursor were selected for antibody expression while acquiring somatic mutations. The latter observation discriminates DLL from classical Hodgkin's disease, where we recently also observed a high load of somatic mutation within rearranged V region genes, but a frequent occurrence of crippling mutations.