bluuebunny/crossref_metadata_2025_split huggingface dataset:
The immune response to Plasmodium chabaudi malaria in interleukin‐4‐deficient mice
Authors: von der Weid Thierry , Kopf Manfred , Köhler Georges , Langhorne Jean 
Published: March 2007

AbstractInterleukin(IL)‐4 promotes the development of T helper (TH)2 cells, induces immunoglobulin class switching to IgG1 and is thought to be essential for switching to IgE. During a primary infection with the erythrocytic stages of Plasmodium chabaudi chabaudi, TH1 and TH2 cells specific for the parasite appear sequentially as infection progresses. To dissect the possible role of TH2 responses at the later stages of infection, mice with a targetted disruption of the IL‐4 gene were infected with P. chabaudi. IL‐4‐deficient mice were able to control and clear a primary infection, although recrudescent parasitemias were significantly higher in these mice compared with wild‐type littermates, demonstrating that IL‐4 per se is not required for parasite elimination. To evaluate the actual impairment of TH2 functions in the absence of IL‐4 in vivo during an infection with P. chabaudi, the cellular and humoral responses to the parasite generated in vitro and in vivo were compared in the two types of mice. Our data indicate that in vitro TH1 responses and ex vivo IL‐12 mRNA levels were sustained in the IL‐4‐deficient mice compared with wild‐type littermates. Correspondingly, TH2‐associated cytokine mRNA such as IL‐5 and IL‐6, but not IL‐10, were reduced early in infection in the deficient animals. However, these cytokines were expressed at comparable levels at the later stages of infection in both types of mice. Reflecting these differences in TH function, IgG1 responses were decreased in vitro and delayed in vivo, whereas IgG2a and IgG2b responses appeared earlier in vivo in the deficient mice. Strikingly, IgE secretion was not blocked in vivo in the deficient mice; the onset of the synthesis of IgE mRNA was delayed during infection and the amount of circulating IgE was five times lower than in the wild‐type littermates after 5 weeks of infection. All these impairments of TH‐related activities were insufficient to affect parasite clearance in the deficient mice, probably due to the fact that such activities were only delayed and could take place normally at the later stages of infection.
Immunological approach to inhibit formation of anti‐antibodies to allo‐ and xenogeneic anti‐T cell immunoglobulin
Authors: Mysliwietz Josef , Thierfelder Stefan , Mocikat Ralph , Kremmer Elisabeth 
Published: March 2007

AbstractInhibitory anti‐antibodies induced in patients by xenogeneic or even by humanized anti‐T cell antibodies remain an unresolved problem. Mice also produce anti‐antibodies following injection of xeno‐ or allogeneic anti‐T cell antibodies. Here we report a principle based on sequentially applied anti‐T cell antibodies generated in different species, which results in suppressed anti‐antibody formation and prolonged immunosuppression. Thus, a single priming injection in mice of mouse (MmT1 or MmT5 differing by idiotype only) or of rat (RmT1) anti‐mouse Thy‐1 monoclonal antibodies (mAb) or of rat anti‐mouse L3T4 + Ly‐2 (RmCD4 + CD8) mAb suppressed anti‐antibody formation against subsequent booster injections of one of the above antibodies, provided that they differed in species origin from the priming antibody. Correspondingly, a sixfold and longer prolongation of 50% survival of fully mismatched skin grafts was observed. Less or no anti‐antibody suppression and little prolongation of graft surival was obtained if the ‘first’ and the ‘second’ (and following) antibody injections were of the same species, differing by iso‐ or idiotype only. Finally, the suppressive principle did not manifest itself at all if the initial antibody injection included both the first and second antibody. These findings are discussed with reference to earlier studies on hapten/carrier effects as well as on immunosuppression attributed to ‘non‐depleting’ rat anti‐CD4/CD8 T cell antibodies.
Identification of T cell receptor recognition residues for a viral peptide presented by HLA B27
Authors: Bowness Paul , Allen Rachel L. , McMichael Andrew J. 
Published: March 2007

AbstractThe fine specificity of T cell recognition of peptide analogues of the influenza nucleoprotein epitope, NP 383–391 SRYWAIRTR, was studied using HLA B27‐restricted influenza‐specific cytotoxic T cell (CTL) clones, of defined T cell receptor (TcR) usage, derived from unrelated individuals following natural infection. Even conservative amino acid substitutions of the peptide residues P4, P7 and P8 influenced CTL recognition. These side chains are probably directly contacted by the TcR. CTL clones which used the TcR Vα14 gene segment (but not those using TcR Vα12) were also sensitive to P1 substitutions, suggesting that the TcR α chain of these clones lies over the N terminus of bound peptide, and that the “footprint” of certain TcR can span all exposed residues of a peptide bound to a major histocompatibility complex class I molecule.These results, taken together with previous structural and functional data, suggest that, for nonamer peptides bound to HLA B27, P1, P4 and P8 are “flag” residues with TcR‐accessible side chains.
Cross‐linking CD28 leads to activation of 70‐kDa S6 kinase
Authors: Pai Sung‐Yun , Calvo Victor , Wood Michael , Bierer Barbara E. 
Published: March 2007

AbstractProliferation of T lymphocytes in response to antigen/MHC complexes is dependent upon the presence of a co‐stimulatory signal; in its absence, T cells are rendered unresponsive to specific antigen. CD28 is a T cell surface glycoprotein that acts as a co‐stimulatory molecule when combined with signals initiated by the T cell receptor‐CD3 complex. While the biochemical signaling events following CD28 stimulation are still poorly defined, monoclonal antibodies (mAb) directed against CD28 have been shown to transduce a variety of early signals that are different in the presence of cross‐linking antibody or the presence of phorbol 12‐myristate 13‐acetate (PMA), an activator of protein kinase C (PKC). Stimulation of human T cells with cross‐linked anti‐CD28 mAb alone resulted in the activation of 70‐kDa (p70) S6 kinase, a rapamycin‐sensitive serine/threonine kinase that is believed to be important for cell cycle progression. Activation of p70 S6 kinase through CD28 was inhibited by rapamycin. Activation of p70 S6 kinase also increased in response to cross‐linked CD3, but followed a more rapid time course than activation via CD28. Cyclosporin A and FK506 had no effect on p70 S6 kinase activity initiated via either pathway. The combination of cross‐linked CD28 and cross‐linked CD3 had no more than an additive effect on the induction of p70 S6 kinase activity. Thus, recruitment of p70 S6 kinase activity appears to represent a common signal transduction event shared by both the CD28 and CD3 pathways of T cell activation.
Induction of HIV‐1 envelope (gp120)‐specific cytotoxic T lymphocyte responses in mice by recombinant CHO cell‐derived gp120 is enhanced by enzymatic removal of N‐linked glycans
Authors: Doe Barbara , Steimer Kathelyn S. , Walker Christopher M. 
Published: March 2007

AbstractPriming of CD8+ cytotoxic T lymphocyte (CTL) responses with recombinant proteins has been facilitated by the development of novel adjuvants that deliver antigens into the class I major histocompatibility complex (MHC) pathway. However, the extent to which secondary structure or glycosylation of these proteins prevents priming of class I MHC‐restricted CTL responses is not clear. To address this issue, recombinant HIV‐1 gp120 envelope proteins produced in yeast, insect, or mammalian cells were compared for the ability to elicit CD8+ CTL activity in mice. Envelope‐specific CD8+ T lymphocytes were detected in BALB/c mice immunized with env 2‐3, a 55‐kDa yeast‐derived envelope protein that is not glycosylated and lacks a native conformation. This response was directed against a previously described epitope in the V3 region of gp120, as well as a newly identified epitope located near the carboxy‐terminus of the molecule. Similar levels of V3‐directed CTL activity were observed in mice immunized with recombinant gp120 produced in insect (Spodoptera fugiperda) cells using a baculovirus expression system (gp120BAC). In contrast, induction of CTL responses was considerably less efficient when mice were immunized with gp120CHO, a native, fully glycosylated envelope protein produced in mammalian CHO cells. Denaturation of gp120CHO prior to immunization was not sufficient to prime CTL responses. However, envelope‐specific CD8+ CTL activity was elicited when N‐linked glycans were removed by treatment with an endoglycosidase. Possible mechanisms by which N‐linked glycans influence delivery or processing of recombinant proteins for class I MHC presentation, and the implications of these findings for the design of subunit vaccines, are discussed.
Mechanisms in CD4 antibody‐mediated transplantation tolerance: kinetics of induction, antigen dependency and role of regulatory T cells
Authors: Scully Ralph , Qin Shixin , Cobbold Stephen , Waldmann Herman 
Published: March 2007

AbstractCBA/Ca mice may be made tolerant to minor histoincompatible B10.BR skin grafts by treatment with a short course of non‐depleting anti‐mouse CD4 and CD8 monoclonal antibodies (mAb), during the transplantation period. We wished to determine when, in relation to antibody therapy, the T cells became tolerant. This was investigated by a series of adoptive transfer experiments in which mAb‐treated cells were removed from therapeutic antibody at defined times after skin grafting, and exposed to fresh antigen in the absence of further mAb treatment. We show here that T cells do not become fully tolerant until 5 weeks after skin grafting. If antibody therapy is continued for the full 5 weeks, T cell tolerance can still be established, suggesting that antibody therapy does not prevent lymphocytes from registering the presence of antigen. Once the tolerant state is established, it is difficult to break that tolerance by lymphocyte infusions from normal donors. This “resistance” is mediated by T cells of the tolerant host. We show that the maintenance of both tolerance and “resistance” requires a continuous supply of antigen. When tolerant cells were “parked” in T celldepleted mice, tolerance and “resistance” were eventually lost by 6 months. In contrast, “parked” cells exposed to fresh antigen at any time up to 4 months remained tolerant and “resistant” indefinitely. Finally, we wished to establish whether “resistance” was peculiar to this form of peripheral tolerance, or whether it might also be present in tolerance considered to be classically central. We observed resistance to be greater in the mAb‐treated peripherally tolerant group, but noted that some of the centrally tolerant animals also exhibited a level of resistance above that of T cell‐ablated controls. This suggests that a tolerance mechanism whose role is only minor in central tolerance may have a major role in antibody‐mediated peripheral tolerance.
The balance between deletion and activation of CD4+8+ thymocytes is controlled by T cell receptor‐antigen interactions and is affected by cyclosporin A
Authors: Curnow S. John , Schmitt‐Verhulst Anne‐Marie 
Published: March 2007

AbstractThe sensitivity of immature thymocytes to antigen‐induced deletion has been shown to correlate with their differentiation status. By using an in vitro approach we have investigated whether parameters of antigenic stimulation may also affect the response of thymocytes. Two T cell receptor (TcR)‐transgenic (Tg) mouse models have been compared, both of which recognize the allo‐antigen H‐2Kb but are functionally CD8“‐dependent” (KB5.C20‐Tg) and “‐independent” (BM3.3‐Tg). Presentation of the antigen H‐2Kb on the surface of fibroblasts, to thymocytes in vitro, resulted in the apoptosis of CD4+8+ thymocytes. In contrast to in vivo deletion, in vitro deletion was much greater for KB5.C20‐Tg than for BM3.3‐Tg. In the absence of engagement of CD8 (using an altered H‐2Kb‐α3 domain or CD8‐specific antibodies), the H‐2Kb‐induced deletion of CD4+8+ thymocytes was decreased for KB5.C20‐Tg, but no change in the pattern of deletion for BM3.3‐Tg occurred. CD4+8+ thymocytes which remained viable after in vitro exposure to antigen, were shown to have been activated. Cyclosporin A (CsA), which has been reported to inhibit activation‐induced cell death, did not affect antigen‐induced deletion of CD4+8+ thymocytes from KB5.C20‐Tg. More strikingly, deletion of CD4+8+ thymocytes from BM3.3‐Tg increased, whilst activation was partially inhibited by CsA. These results provide direct evidence that presentation of antigen to thymocytes can result in deletion or activation, depending on not only the differentiation status of the cell, but also parameters of TcR‐antigen interaction. Additionally, the effects of CsA suggest that activation can prevent the induction of deletion.
Comparison of the Jβ gene usage among different T cell receptor Vβ families in spleens of C57BL/6 mice
Authors: Kato Tomohiro , Suzuki Satoshi , Sasakawa Hiroko , Masuko Kayo , Ikeda Yoko , Nishioka Kusuki , Yamamoto Kazuhiko 
Published: March 2007

AbstractTo clarify whether there is a bias in the V‐D‐J combination of T cell receptor (TcR) genes, Jβ gene usage has been investigated in a total of 743 TcR β genes of Vβ2, Vβ8.2, and Vβ14 families expressed in C57BL/6 mouse spleens. Genes of TcR β chains, amplified by a reverse transcriptase‐polymerase chain reaction, were individually cloned into plasmids. Cloned genes (61 to 106), randomly selected in each respective Vβ family from three different mice, were tested by means of hybridization with 12 oligo DNA probes which were designed to differentiate 12 murine functional Jβ gene segments. The results are enumerated below. (1) The Jβ2.6 gene segment was found to be most frequently used (Vβ2, 19.8%; Vβ8.2, 21.2%; and Vβ14, 19.2%). In contrast, usage of the Jβ1.6 gene segment was most infrequent (Vβ2.1.9%; Vβ8.2, 2.9%; and Vβ14, 0.5%); (2) High frequency of the Jβ2.1 gene segment and low frequency of the Jβ1.3 and Jβ1.5 gene segments were also observed; (3) The Jβ2 cluster was used in preference to the Jβ1 cluster (usages of the Jβ2 cluster: Vβ2, 67.8%; Vβ8.2, 65.9%; and Vβ14, 70.4%); and (4) These biases were generally common to all three Vβ families examined and differences among individual mice were mostly small. Considering these findings, we conclude that the TcR Jβ gene segments in C57BL/6 mice splenocytes are selected with a bias, but are selected independently of the Vβ families.
Differential expression of mRNA encoding interleukin‐12 p35 and p40 subunits in situ
Authors: Bette Michael , Jin Shen‐Chu , Germann Tieno , Schäfer Martin K.‐H. , Weihe Eberhard , Rüde Erwin , Fleischer Bernhard 
Published: March 2007

AbstractInterleukin‐12 (IL‐12) is a heterodimeric cytokine that plays an important role in the regulation of the immune response. For biological activity the expression of both subunits of IL‐12, p35 and p40, is required. Moreover, in the mouse the p40 chain of IL‐12 specifically inhibits the effects of the IL‐12 heterodimer. In the present study we have analyzed by in situ hybridization the expression of the p35 and p40 mRNA in the spleens of BALB/c and mutant (SCID, nude, beige) mice, unstimulated and after in vivo stimulation with lipopolysaccharide (LPS) and with staphylococcal enterotoxin B (SEB). In unstimulated spleens of BALB/c mice, p35 and p40 mRNA were only detectable in a few strongly stained single cells, p35 mRNA was expressed in addition weakly in the B cell areas. After injection of LPS or SEB, p40 mRNA was strongly induced in the T cell areas all over the spleen, whereas expression of p35 mRNA and its distribution pattern did not change. Surprisingly, most of the mRNA for p35 and p40 was localized in different areas of the spleen and was apparently produced by different cells. In macrophage‐depleted spleens the increased expression of p40 mRNA in response to LPS was reduced but still detectable, demonstrating that other cells besides macrophages can up‐regulate IL‐12 p40 mRNA. Nude mice showed a stronger expression of p35 mRNA, SCID mice lacked the weak p35 staining of the B cell areas but showed a strong basal expression of both p35 and p40 mRNA and a focal response to LPS. The pattern of IL‐12 mRNA expression in beige mice was the same as in normal mice. These data demonstrate a spatial dissociation of expression of the two chains of IL‐12 and are compatible with a regulatory role of the isolated IL‐12 p40 chain in vivo. In addition, they indicate that the demonstration of mRNA for both chains of IL‐12 in whole tissues or cell mixtures is not necessarily indicative of functional IL‐12.
Co‐stimulation with LFA‐1 triggers apoptosis in γδ T cells on T cell receptor engagement
Authors: Matsumoto Yoshihiro , Hiromatsu Kenji , Sakai Tetsu , Kobayashi Yasushi , Kimura Yuki , Usami Jun , Shinzato Toru , Maeda Kenji , Yoshikai Yasunobu 
Published: March 2007

AbstractStimulation of T cells through the T cell receptor (TcR) initiate activation pathways, and paradoxically can also result in activation‐induced cell death. Many factors influence a stimulated cell's decision to manifest one or the other. Here we show that co‐stimulation with LFA‐1 plays a key role in the choice between the two fates, differentiating between αβ and γδ T cells. Peripheral γδ T cells but not αβ T cells undergo apoptosis upon co‐cross‐linking of TcR and LFA‐1 in MRL lpr/lpr mice as well as +/+ mice. Our results suggest that apoptosis of γδ T cells is inducible by combined stimuli independent of the Fas‐mediated pathway.
Peptide antagonists that promote positive selection are inefficient at T cell activation and thymocyte deletion
Authors: Barnden Megan J. , Heath William R. , Rodda Stuart , Carbone Francis R. 
Published: March 2007

AbstractWe set out to determine whether thymocytes from T cell receptor (TCR) transgenic animals specific for a class I‐restricted determinant from ovalbumin (OVA) showed the same fine specificity for antigen‐driven deletion in single‐cell suspension culture as required for mature T cell activation. The transgenic TCR is specific for the Kb‐restricted peptide OVA257‐264 (SIINFEKL) which is known to have four TCR contact residues at position 1, 4, 6, and 7 from the crystal structure of this fragment in complex with Kb. OVA257‐264 analogs systematically substituted at each of these positions were assayed for their ability to promote immature double‐positive thymocyte deletion or mature T cell activation of a cytotoxic T lymphocyte line derived from this transgenic mouse. In the absence of additional antigen‐presenting cells, single‐cell thymocyte suspensions showed that the specificity for double‐positive thymocyte deletion and mature T cell activation was virtually identical, demonstrating a limited cross‐reactivity with a number of variants having conservative substitutions at these exposed residues. These peptides were considerably more efficient at both thymic deletion and mature T cell activation than a number of non‐conservative substitution analogs known to act as antagonists of OVA257‐264 and capable of selecting transgenic T cells in thymic organ culture. Therefore, both peripheral T cell activation and thymic deletion have an overall similar pattern of peptide specificity which differs from that required for positive selection. This suggests that a subset of major histocompatibility complex‐presented peptides could promote positive selection without causing either thymic deletion or peripheral activation of those selected T cells.
Induction of tolerance in freshly isolated alloreactive CD4+ T cells by activated T cell stimulators
Authors: Satyaraj Ebenezer , Rath Satyajit , Bal Vineeta 
Published: March 2007

AbstractActivated human T cells express major histocompatibility complex class II proteins, and their potential to present antigens to T cell clones has been documented extensively. The effect of such T‐T presentation on responder T cell clones has been shown to be the induction of tolerance, sometimes accompanied by activation. To investigate whether freshly isolated responder T cells are also susceptible to such induction of tolerance by activated T cells functioning as antigen‐presenting cells (APC), we have used the capability of unprimed ex vivo T cells to respond in a proliferation assay in vitro to alloligands on professional APC. We show that purified human T cells ex vivo, when exposed to alloligand on activated T cells for primary allorecognition In vitro, fail to mount a proliferative response. Priming of responder CD4+ T cells with alloligand expressed on activated T cells results in the induction of nonresponsiveness to a subsequent challenge by competent allo‐APC. This ability of activated, HLA‐DR+ T cells to induce nonresponsiveness to subsequent challenge in bulk CD4+ T cell populations ex vivo has interesting implications for infections involving T cells such as human immunodeficiency virus.
The role of protein kinase C in the regulation of extracellular signal‐regulated kinase by the T cell antigen receptor
Authors: Izquierdo Manolo , Leevers Sally J. , Williams David H. , Marshall Chris J. , Weiss Arthur , Cantrell Doreen 
Published: March 2007

AbstractThe aim of this study was to explore the role of protein kinase C (PKC) in the activation of mitogen‐activated protein kinases (MAPK) in T lymphocytes. The MAPK extracellular signal‐regulated kinase‐2 (ERK2) is activated in response to phorbol esters which stimulate PKC, by transient expression of a constitutively active ras mutant, by cell activation via the G protein‐coupled type 1 muscarinic acetylcholine receptor (HM1R) or in response to triggering of the T cell antigen receptor (TCR). The relative contribution of PKC to TCR and HM1R regulation of ERK2 was explored by examining the effects of a PKC inhibitor (Ro 31‐8425) on ERK2 activation. The data demonstrate that phorbol ester and HM1R regulation of ERK2 was prevented by the PKC inhibitor, but that the inhibitor had no effect on ERK2 activation induced by expression of a constitutively active ras mutant p21v‐Ha‐ras. Furthermore, the TCR stimulates both PKC and p21ras but TCR regulation of ERK2 was only weakly suppressed by the PKC inhibitor. These data indicate that PKC has a potential but not a predominant role in TCR regulation of ERK2.