bluuebunny/crossref_metadata_2025_split huggingface dataset:
Binding of a major T cell epitope of mycobacteria to a specific pocket within HLA‐DRw17(DR3) molecules
Authors: Geluk Annemieke , Bloemhoff Wim , De Vries René R. P. , Ottenhoff Tom H. M. 
Published: March 2007

AbstractCD4+ T cells recognize antigenic peptides bound to the polymorphic peptide‐binding site of major histocompatibility complex (MHC) class II molecules. The polymorphism of this site is thought to dictate which peptides can be bound and thus presented to the T cell receptor. The mycobacterial 65‐kDa heat‐shock protein (hsp65) peptide 3‐13 is an important T cell epitope: it is immunodominant in the mycobacterium‐specific T cell response of HLA‐DR3+ individuals but, interestingly cannot be recognized in the context of any other HLA‐DR molecules. We, therefore, have tested whether the hsp65 epitope p3‐13 is selected for T cell recognition in the context of only HLA‐DR3 molecules by an unique binding specificity for HLA‐DR3. Using biotinylated peptides and EBV‐transformed BLCL comprising all known HLA class II specificities, we find that p3‐13 binds to HLA‐DRw17(DR3) but not to any other HLA‐DR molecule. Conversely, a control peptide p307‐319 influenza hemagglutinin binds to all known HLA‐DR molecules but only weakly to HLA‐DRw17 and HLA‐DR9. Peptide binding could be inhibited by excess unbiotinylated competitor analogue as well as by anti‐DR monoclonal antibodies but not by anti‐class I‐, anti‐DP‐ or anti‐DQ monoclonal antibodies.The amino acid sequence of DRw17 molecules differs uniquely at five positions from the other DRβ1 sequences. Three of these five residues (positions 26, 71 and 74) are potential peptide contacting residues. These residues map closely together in the hypothetical three‐dimensional model of the DR molecule and, thus, most probably form a positively charged pocket, critical for the binding of p3‐13. Interestingly, p3‐13 does not bind to a DR3 variant, the DRw18 molecule. The DRw18β1 chain differs from DRw17 at two major positions, close to or within the DRw17‐specific pocket. These substitutions drastically change the structure and charge of the pocket and thus presumably abrogate its ability to bind p3‐13.
Memory in helper T cells of minor histocompatibility antigens, revealed in vivo by alloimmunizations in combination with Thy‐1 antigen
Authors: Lightstone Elizabeth , Marvel Jacqueline , Mitchison Avrion 
Published: March 2007

AbstractA cooperative antibody response in which T helper (Th) cells recognize minor histocompatibility antigens (mha) and B cells recognize Thy‐1 antigen, is used to explore memory in the T cell compartment. In contrast to B cell memory, Th memory reaches a plateau rapidly, although Th memory of Thy‐1 itself (or an associated antigen) behaves exceptionally in this respect. The plateau then extends over several weeks at least. Single mha, among them H‐Y, generate detectable memory. Incompatible H‐2 antigens, including class I antigens on their own, inhibit this response through what appears to be a mechanism of intracellular antigenic competition. Antigen presentation in this system is by host cells, as judged by lack of donor‐specific restriction. Memory resides in both the CD45RA+ and CD45RA− compartments, although the majority of memory Th cells have the latter phenotype.
Sequence variation of cytotoxic T cell epitopes in different isolates of Epstein‐Barr virus
Authors: Apolloni Ann , Moss Denis , Stumm Robyn , Burrows Scott , Suhrbier Andreus , Misko Ihor , Schmidt Chris , Sculley Tom 
Published: March 2007

AbstractPrevious results have identified two distinct cytotoxic T lymphocyte (CTL) epitopes encoded by Epstein‐Barr virus (EBV), TETA (ORF BLRF3/BERF1 residues 329‐353) and EENL (ORF BERF3/BERF4 residues 290‐309). Measurement of the specificities of CTL clones (TETA‐specific clone 13 and EENL‐specific clone 7) directed against these epitopes indicated that the EENL epitope is conserved in all strains of EBV tested while the TETA epitope varied between individual virus strains. Sequencing of the DNA regions encoding these two CTL epitopes in different EBV isolates confirmed these interpretations and demonstrated that different TETA epitope sequences were encoded by B‐type EBV strains and by the B95‐8 isolate of EBV compared to the other A‐type EBV strains. Titration of synthetic variants of the TETA epitope revealed that the epitope encoded by B95‐8 was 15‐fold less efficient as a T cell epitope than the sequence encoded by other A‐type viral strains while the TETA variant encoded by the B‐type strains displayed essentially no activity as a T cell epitope.
In vitro biosynthesis of complement factor I by human endothelial cells
Authors: Julen Nathalie , Dauchel HÉLÈNe , Lemercier Claudie , Sim Robert B. , Fontaine Marc , Ripoche Jean 
Published: March 2007

AbstractWe have studied the secretion of the complement regulatory protein factor I by human umbilical vein endothelial cells (HUVEC). Northern and Western blot analysis and biosynthetic labeling experiments indicate that HUVEC secrete factor I at very low levels in basal conditions and that this secretion is significantly enhanced by interferon‐γ. Analysis of the proteolytic inactivation of C3b by HUVEC supernatants show that factor I is secreted in a functional form and can promote the specific proteolytic inactivation of C3b to iC3b. Together with previous studies establishing the secretion of complement factor H by HUVEC, this work demonstrates that the endothelial cell is able to secrete in its environment two complement regulatory proteins, factor I and factor H, which can mediate the degradation of C3b to iC3b. The secretion of factor I by HUVEC provides a useful in vitro model to analyze the modulation of this secretion and may be relevant to the local deposition of iC3b at the surface of the endothelium during the inflammatory reaction.
CD4+ T cell‐mediated killing of major histocompatibility complex class II‐positive antigen‐presenting cells (APC) III. CD4+ cytotoxic T cells induce apoptosis of APC
Authors: Grogg Daniel , Hahn Sinuhe , Erb Peter 
Published: March 2007

AbstractA subset of CD4+ T cells, belonging to the T helper type 1 (Th1) cells, kills antigen‐presenting cells (APC) in an antigen‐specific and major histocompatibility complex (MHC) class II‐restricted way. Evidence is presented that CD4+ cytotoxic T lymphocytes (CTL) induce apoptosis or programmed cell death within susceptible APC as witnessed by quantitative DNA fragmentation. Apoptosis is more reliable to determine cell death than the 51Cr‐release assay, because some cells demonstrate resistance to CD4‐mediated lysis in the 51Cr‐release assay. Apoptosis becomes manifest after 2 to 4 h of incubation preceding the disintegration of the target cells which is detectable between 12 and 24 h as measured by the 51Cr‐release assay. Unstimulated B cells, which are not killed, but function as APC, do not undergo apoptosis, whereas lipopolysaccharide or anti‐μ‐activated B cell blasts show apoptosis and are efficiently lysed. Several CD4+ Th2‐type cells tested, which did not demonstrate killing of APC as measured by the 51Cr‐release assay, are unable to mediate programmed cell death of appropriate APC. Actinomycin D or cycloheximide, inhibitors of transcription and translation, respectively, fail to prevent apoptosis of APC excluding the involvement of newly synthesized soluble products as mediators of killing. Pretreatment of CD4+ CTL, but not of APC with 4,4′‐diisothiocyanato‐stilbene‐2,2′‐disulfonic acid, a specific inhibitor of the anion transport, efficiently prevents apoptosis of APC, although the secretion of interleukins is not affected. We propose, that upon contact of the CD4+ CTL with APC, molecules of yet undefined nature are activated and released in a polar fashion at the contact site and induce the endogenous pathway of programmed cell death.
Synergism between tumor necrosis factor‐α and interferon‐γ on macrophage activation for the killing of intracellular Trypanosoma cruzi through a nitric oxide‐dependent mechanism
Authors: Muñoz‐Fernández M. Angeles , Fernández Monica A. , Fresno Manuel 
Published: March 2007

AbstractIntracellular replication of the protozoan parasite Trypanosoma cruzi inside macrophages is essential for the production of the disease and the development of the parasite. Two CD4+ T cell lines, A10 and A28, were established from T. cruzi‐infected BALB/c mice which specifically proliferated to parasite antigens. The trypanocidal activity of BALB/c macrophages was induced upon culture with the A10, but not with the A28 T cell line. The cell‐free supernatant from this A10 line, as well as from immune spleen cells stimulated with specific antigen or concanavalin A, but not from the A28 T cell line also activated the trypanocidal activity of peritoneal macrophages or of the J774 macrophage‐like cell line. When the lymphokine content of the supernatants from both cell lines was analyzed, it was found that the A10 T cell line secreted interferon (IFN)‐γ, tumor necrosis factor (TNF)‐α and interleukin 2, whereas the A28 line did not secrete IFN‐γ upon stimulation. Furthermore, the trypanocidal‐inducing ability of A10 supernatant was completely abrogated by neutralizing anti‐IFN‐γ antibodies and partially abrogated by neutralizing anti‐TNF‐α antibodies. When recombinant cytokines were added to J774 cells, IFN‐γ was able to induce significant trypanocidal activity whereas TNF‐α was almost ineffective. However, TNF‐α or lipopolysaccharide (LPS) showed a synergistic effect with IFN‐γ on macrophage activation. IFN‐γ triggered nitric oxide (NO) synthesis by J774 cells whereas TNF‐α was almost ineffective. TNF‐α and LPS were also synergistic with IFN‐γ in the NO production. Both the NO production and the trypanocidal activity in J774 cells induced by T cell supernatants or lymphokine combinations were inhibited by N‐monomethyl‐L‐arginine, a competitive inhibitor of NO synthase activity. A good correlation between the levels of NO production and trypanocidal activity induced by different lymphokine preparations was found. Those results suggest that IFN‐γ and TNF‐α, secreted by T. cruzi‐immune T cells, are involved in the activation of the trypanocidal activity of mouse macrophages through an NO‐dependent mechanism.
A single autosomal gene defect severely limits IgG but not IgM responses in B lymphocyte‐deficient A/WySnJ mice
Authors: Miller David J. , Hanson Keith D. , Carman Julie A. , Hayes Colleen E. 
Published: March 2007

AbstractAntigen‐stimulated B lymphocytes either differentiate into IgM‐secreting plasma cells or into memory B cells that secrete other immunoglobulin isotypes upon antigen restimulation. The mechanisms that generate and maintain memory B cells are poorly understood. Previously, we described a severe B lymphocyte deficiency in adult strain A/WySnJ mice compared to subline A/J. Here we show that the single, autosomal co‐dominant locus responsible for the deficiency also diminishes IgG‐secrcting B cell formation without interfering with IgM‐secreting plasma cell differentiation. A/WySnJ secondary IgG1 responses to the protein antigens hemocyanin, bovine γ‐globulin, ovalbumin, lysozyme and β‐galactosidase were 6‐ to 50‐fold lower than A/J responses. The defect also decreased secondary IgG2a and IgG3 responses, and primary IgG1 and IgG2a responses. The reduced A/WySnJ secondary IgG1 response was not due to differential response kinetics or dose responsiveness, and could not be augmented to A/J levels by repeated immunizations. Serum IgG1, IgG2a and IgG3 levels from nonimmune A/WySnJ mice were similarly reduced. The secondary IgG1 response and splenic B cell percentage showed significant positive correlation (r = 0.72) in F2 mice, suggesting that a single locus controlled both traits. In contrast, A/WySnJ mice made good primary IgM responses to hemocyanin, β‐galactosidase, and the thymus‐independent antigen trinitrophenyl‐Ficoll. The A/WySnJ splenic adherent cells were competent in antigen‐presenting function, and A/WySnJ immune T cells proliferated in response to antigen and provided the requisite B cell stimulatory signals for an IgG1 response. Together, our results suggest that A/WySnJ mice have a genetic lesion that causes a selective IgG immune response dysfunction. The absence of IgG‐secreting cell precursors or a defect in precursor activation or differentiation are two possible mechanisms which could precipitate a selective IgG response dysfunction. We propose that the defective A/WySnJ and normal A/J strain pair offer the opportunity to use a natural genetic variation as a tool to investigate B lymphocyte development and function.
Cross‐reaction of antibodies to the nine‐amino acid repeats of Plasmodium falciparum antigen 11.1 with human serum albumin
Authors: Mercereau‐Puijalon Odile , Guillotte Micheline , Doyen Noëlle 
Published: March 2007

AbstractMice immunized with the recombinant antigen 11.1 β‐galactosidase, consisting of 22 repeats of the nine‐amino acid unit from Plasmodium falciparum antigen 11.1, produced antibodies reacting with human serum albumin. A positive reaction was observed in dot‐blot assays, in enzyme‐linked immunosorbent assay and on immunoblots of sodium dodecyl sulfate polyacrylamide gels as well as twodimensional gels. Binding was specific for human albumin, as no reaction could be detected on bovine serum albumin, hen egg ovalbumin, rat serum albumin or another abundant human serum protein, the α2‐macroglobulin. In addition, rabbit antibodies raised to human serum albumin reacted with keyhole lympet hemocyanin coupled to synthetic dimers of the nine‐amino acid repeats of the P. falciparum 11.1 antigen. These data indicate antigenic relationship between the 11.1 antigen and human albumin. The proteins have a short sequence of homology in a region where human serum albumin differs from the albumins of other species.
Preferential positive selection of Vα2+CD8+ T cells in mouse strains expressing both H‐2k and T cell receptor Vαa haplotypes: determination with a Vα2‐specific monoclonal antibody
Authors: Pircher Hanspeter , Rebai Najet , Groettrup Marcus , Grégoire Claude , Speiser Daniel E. , Happ Mary Patt , Palmer Ed , Zinkernagel Rolf M. , Hengartner Hans , Malissen Bernard 
Published: March 2007

AbstractA monoclonal antibody, B20.1, was generated by fusing spleen cells from a Lou rat immunized with a soluble α/β T cell receptor (TcR; Vα2/Vβ2) to mouse myeloma cells. Analysis of a panel of Vα2 mRNA‐expressing T cell lines, hybridomas and transfectants revealed that the B20.1 antibody was specific for murine TcR Vα2 chains. The Vα2+ T cell population was examined in various inbred strains by two‐color immunofluorescence using B20.1 and CD4‐ and CD8‐specific antibodies with the following results: (a) the B20.1 antibody detected most members of the TcR Vα2 subfamily in the four TcR Vα haplotypes tested; (b) in most strains examined, TcR Vα2 expression was biased to the CD4 subset (7.4%‐17.4% Vα2+ T cells) as compared to the CD8 compartment (3.8%‐13.3%); (c) TcR Vα2 expression was not influenced by Mls gene products and (d) increased positive selection of Vα2+CD8+ T cells by H‐2k major histocompatibility complex molecules occurred in all murine strains tested of the TcR Vαa, but not in those bearing the TcR Vαb haplotype.
Engagement of major histocompatibility complex class I and class II molecules up‐regulates intercellular adhesion of human B cells via a CD11/CD18‐independent mechanism
Authors: Alcover Andrés , Juillard Véronique , Acuto Oreste 
Published: March 2007

AbstractWe have studied the role of major histocompatibility complex (MHC) molecules in the regulation of intercellular adhesion of human B cells. We found that molecules able to bind to MHC class II molecules, such as monoclonal antibodies or staphylococcal enterotoxins, induced rapid and sustained homotypic adhesion of Epstein‐Barr virus (EBV)‐transformed B cell lines as well as peripheral blood B lymphocytes. Moreover, anti‐MHC class I monoclonal antibodies also stimulated intercellular adherence. Adhesion induced upon MHC engagement was faster and stronger than that triggered by phorbol esters. It needed active metabolism, but divalent cations were not required. Monoclonal antibodies directed against LFA‐1 (CD11a/CD18) or its ligand ICAM‐1 (CD54) did not inhibit MHC class II‐induced homotypic adhesion of various EBV‐transformed B cell lines, nor of a variant of the B cell line Raji expressing very low LFA‐1 surface levels. Moreover, EBV‐transformed B cells from a severe lymphocyte adhesion deficiency patient, lacking surface CD11/CD18, also aggregated in response to anti‐MHC class I or class II monoclonal antibodies. Together these data indicate that engagement of MHC molecules may transduce signals to B cells resulting in up‐regulation of intercellular adhesion, via an LFA‐1‐independent mechanism. This may play a role in the stabilization of T cell / antigen‐presenting cell conjugates at the moment of antigen recognition.
A unique CD44 monoclonal antibody identifies a new T cell activation pathway
Authors: Pierres Anne , Lipcey Carol , Mawas Claude , Olive Daniel 
Published: March 2007

AbstractWe have identified a new T cell activation pathway mediated by the lymphocyte homing receptor/CD44 molecule. 8B2.5, a local monoclonal antibody (mAb), which recognizes two glycoproteins of 85 and 220 kDa with wide tissue distribution, is shown by sequential immunoprecipitations and competitive antibody‐binding inhibition experiments with several CD44 reference mAb to recognize the CD44 molecule. The 8B2.5 mAb, but not reference CD44 mAb, is able to induce resting peripheral blood lymphocytes to proliferate in the presence of phorbol esters. This proliferation is monocyte dependent but Fc independent and results from 8B2.5 mAb binding to CD44 molecules both expressed by both T cells and monocytes. In the absence of monocytes, proliferation can be restored by solid‐phase 8B2.5 mAb, or, to a lesser extent, by adding interleukin 2. Although CD3 and CD44 surface molecules are found physically independent, T cell activation via the CD44 pathway is inhibited by CD3 modulation. In addition to the direct role of CD44 molecules in T cell proliferation, CD44 mAb can up‐ or‐ down‐regulate the CD3 and CD28 pathways, depending on the presence of monocytes. These results suggest that T cell and monocyte binding to high endothelial venule or extracellular matrix proteins could further promote clonal expansion of resting T cells migrating in certain specific anatomic sites.
A defect in the presentation of intracellular viral antigens is restored by interferon‐γ in cell lines with impaired major histocompatibility complex class I assembly
Authors: Sibille Catherine , Gould Keith , Hämmerling Günter , Townsend Alain 
Published: March 2007

AbstractSurface expression of the majority of class I major histocompatibility complex (MHC) heavy chains is known to require assembly with β2 microglobulin (β2m). To define other factors involved in class I MHC assembly, we have studied two tumor cell lines that are deficient in cell surface class I (H‐2) expression. The BC2 fibrosarcoma and the CMT lung carcinoma express only intracellular unassociated heavy chains despite the presence of β2m. As described previously, when these cell lines are treated with interferon‐γ (IFN‐γ), they are capable of assembling and transporting class I molecules to the cell surface. In this study, we have shown that in the absence of IFN‐γ these mutant cells are unable to present intracelluar viral antigens, although they can be lysed by specific cytotoxic T lymphocyte (CTL) after pre‐incubation with the corresponding synthetic peptide. Flow cytometric analysis demonstrated that extracellular peptide was capable of increasing twofold the surface expression of β2m‐heavy chain complexes. Furthermore, immunoprecipitation experiments confirmed that peptide stabilizes chain association in the BC2 cell lysates. However, infecting these mutants with vectors expressing either pre‐processed antigen or rapidly degraded antigen, failed to overcome their defect in the presentation of endogenous peptide to specific CTL or to mediate surface expression of class I MHC. Preincubation with IFN‐γ completely reversed the endogenous peptide presentation defect, even in mutant cells transfected with a vector encoding a cDNA for the H‐2 molecule restricting CTL recognition. This last result suggests that IFN‐γ corrects the defect by a mechanism separate from simple enhancement of the number of class I molecules produced by the cell. Because there is growing evidence that endogenous peptides can participate in class I MHC assembly, the defect in these mutants could be ascribed to the lack of access to class I molecules by the endogenous peptide. This would prevent stable association of the heavy and light chains and their subsequent transport. Our data suggests that IFN‐γ reestablishes class I MHC surface expression by restoring access of endogenously synthesized peptide to class I molecules.
Inhibitory activity against sporozoites induced by antibodies directed against nonrepetitive regions of the circumsporozoite protein of Plasmodium vivax
Authors: Millet Pascal , Chizzolini Carlo , Wirtz Robert A. , Bathurst Ian , Broderson J. Roger , Campbell Gary H. , Collins William E. 
Published: March 2007

AbstractIn previous studies, Saimiri sciureus boliviensis monkeys have been immunized with four recombinant proteins reproducing part of the circumsporozoite (CS) protein of Plasmodium vivax sporozoites (NSl81V20, rPvCS‐1. rPvCS‐2, rPv‐CS‐3), or with irradiated sporozoites of P. vivax Salvador I strain. To analyze the antibody response elicited against epitopes located outside the immunodominant repeat region of the CS protein, serum samples from these animals were tested for their ability to inhibit the in vitro development of liver stages of P. vivax VK247 strain, characterized from the other strains only by a specific repeat region on the CS protein. Results indicated that there is at least one protective B‐cell epitope outside the repeat region of the CS protein of P. vivax sporozoites, and that this epitope can be expressed by irradiated sporozoites, rPvCS‐2 and ‐3, but not by rPvCS‐1 or NS181V20. Therefore, we designed peptides from the amino acid sequences present both in rPvCS‐2 and ‐3, but not included in the recombinant proteins rPvCS‐1 and NS181V20. Anti‐peptide antibodies had no activity on the development of sporozoites of P. vivax Salvador I strain, into schizonts in primary culture of Saimiri monkey hepatocytes. In addition, antisporozoite antibodies did not react with any of the peptides. These results suggest that the in vitro inhibition observed in this study could depend upon the conformation of the CS protein. This study also demonstrates that antibody response to unnatural linear epitopes can be induced by immunization with recombinant proteins.