1,720,972 research outputs found
Multivalent conjugates of poly-?-D-glutamic acid from Bacillus licheniformis with antibody F(ab') and glycopeptide ligands
No full textPoly--D-glutamic acid from Bacillus licheniformis is a water-soluble, nontoxic, nonimmunogenic exopolymer. Using synthetic linkers, the -carboxylate side chains of PGA were conjugated to an exposed thiol side chain of an antibody F(ab') fragment, Mc109F4. Analysis of the PGA-Mc109F4 conjugate by gel filtration HPLC revealed a mixture of multivalent conjugates. The PGA-Mc109F4 conjugate retained biological activity, but showed a lower binding affinity to target BCL3B3 cells than free Mc109F4 F(ab')2 by flow cytometry, and a lower efficacy for BCL3B3 growth inhibition than free Mc109F4 F(ab')2. PGA was also conjugated with the free amino group of glycopeptide antibiotic vancomycin. The PGA-vancomycin conjugate showed slightly lower antibacterial activity than free vancomycin versus susceptible Bacillus subtilis, but slightly higher activity versus intrinsically resistant Leuconostoc mesenteroides
Therapeutic efficacy of FcgammaRI/CD64-directed bispecific antibodies in B-cell lymphoma
No full textCD64 (Fc?RI) receptors represent highly potent trigger molecules for activated polymorphonuclear cells (PMN) and mediate lysis of a range of tumors in the presence of appropriate monoclonal antibodies. An huCD64 transgenic mouse model designed to analyze the therapeutic activity of a panel of bispecific F(ab')2(BsAb) in retargeting granulocyte–colony-stimulating factor (G-CSF)–activated PMN against syngeneic B-cell lymphomas is reported. This model allows careful analysis of the individual elements of the therapeutic process. BsAb were directed against immunoglobulin-idiotype (Id), major histocompatibility class II (MHC II), or CD19 on the tumors and huCD64 on the effectors. In vitro cytotoxicity assays and in vivo tumor tracking showed that, provided effectors were activated with G-CSF, all 3 derivatives destroyed and cleared lymphoma cells, with (huCD64?×?MHC II) proving by far the most cytotoxic in vitro. However, though all derivatives delivered some survival advantage, only the [huCD64?×?Id] BsAb provided long-term protection to tumor-bearing animals. These results demonstrate that CD64-recruited cytotoxic effectors operate in vivo but that the (huCD64?×?Id) conferred an additional anti-tumor function essential for long-term protection. T-cell depletion studies demonstrated that this extra therapeutic activity with [huCD64?×?Id] was totally dependent on CD4 and CD8 T cells and that mice, once “cured” with BsAb, were resistant to tumor rechallenge. These findings indicate that CD64 is an effective trigger molecule for delivering cytokine-activated PMN against tumor in vivo and that, provided tumor targets are selected appropriately, CD64-based BsAb can establish long-term T-cell immunity. <br/
A new anti-idiotype antibody capable of binding rituximab on the surface of lymphoma cells
No full textThe chimeric anti-CD20 monoclonal antibody (mAb), rituximab, is an established part of the management of many non-Hodgkin lymphomas. The in vivo action of rituximab remains elusive, and this partially reflects a lack of highly specific reagents to detect rituximab binding at the cell surface. Here we report a new high-affinity mAb (MB2A4) with fine specificity for the idiotype of rituximab. It is able to detect rituximab in vitro, in the presence of high levels of human immunoglobulin G (IgG), in the serum of patients receiving rituximab therapy, and, surprisingly, when rituximab is bound to CD20 on the cell surface. We propose that the anti–idiotype (Id) binds to rituximab molecules bound univalently at the cell surface, facilitated by the relatively high off-rate of rituximab. This reagent provides new insights into the binding of rituximab at the cell surface and demonstrates a mode of binding that could be exploited for the surface detection of other mAbs with clinical and biologic applications
T cell immunity to lymphoma following treatment with anti-CD40 monoclonal antibody
No full textIn this study we demonstrate that treatment with anti-CD40 mAb eradicates a range of mouse lymphomas (BCL1, A31, A20, and EL4), but only when used against i.v. tumor doses in excess of 107 cells. Only partial protection was seen against smaller tumor loads. We saw no evidence that anti-CD40 mAb changed the phenotype of the lymphomas or inhibited their growth in the initial period following treatment, but it did result in a rapid expansion of cytotoxic CD8+ cells that was able to clear the neoplastic disease and provide long-term protection against tumor rechallenge. The CTL responses were blocked by mAb against a range of coreceptors and cytokines, including CD8, B7-1, B7-2, LFA-1, and IFN-{gamma}, but not CD4 or CTLA-4, indicating the presence of a conventional cellular Th1 response. Furthermore, we found evidence of cross-recognition between lymphomas (BCL1 and A20) as measured by cytotoxicity and IFN-{gamma} responses in vitro and using tumor rechallenge experiments, suggesting common target Ags. Finally, although anti-CD40 was shown to stimulate NK cell killing, we could find no role for these cells in controlling tumor growth. These data underline the ability of anti-CD40 mAb to potentiate CTL responses and the potency of cellular immunity in eradicating large quantities of syngeneic tumor.<br/
Control of established melanoma by CD27 stimulation is associated with enhanced effector function and persistence, and reduced PD-1 expression of tumor infiltrating CD8(+) T cells
No full textThe immune response to the tumor can be enhanced by targeting costimulatory molecules on T cells. As the CD70-CD27 costimulatory axis plays an important role in the activation, survival, and differentiation of lymphocytes, we have examined the efficacy of agonistic anti-CD27 antibodies as monotherapies for established melanoma in a murine model. We show that this approach leads to a substantial reduction in the outgrowth of both experimental lung metastases and subcutaneous tumors. Anti-CD27 treatment supports the maintenance of tumor-specific CD8(+) T cells within the tumor, reduces the frequency of FoxP3-expressing CD4(+) T cells within tumors, and potentiates the ability of NK1.1(+) and CD8(+) tumor infiltrating cells to secrete IFN? upon coculture with tumor cells. The enhanced effector function correlated with lower levels of PD-1 expression on CD8(+) T cells from anti-CD27-treated mice. Despite the modulating effect of anti-CD27 on multiple cell types, only CD8(+) T cells were absolutely required for tumor control. The CD4(+) T cells were dispensable, whereas NK1.1(+) cells were needed during early stages of tumor growth but not for the effectiveness of anti-CD27. Thus, CD27-mediated costimulation provides a potent boost to multiple aspects of the endogenous responses to tumor, and may be exploited to enhance tumor immunity
Systemic inflammation modulates Fc receptor expression on microglia during chronic neurodegeneration
Full text linkChronic neurodegeneration is a major worldwide health problem, and it has been suggested that systemic inflammation can accelerate the onset and progression of clinical symptoms. A possible explanation is that systemic inflammation “switches” the phenotype of microglia from a relatively benign to a highly aggressive and tissue damaging phenotype. The current study investigated the molecular mechanism underlying this microglia phenotype “switching.” We show in mice with chronic neurodegeneration (ME7 prion model) that there is increased expression of receptors that have a key role in macrophage activation and associated signaling pathways, including TREM-2, Siglec-F, CD200R, and IgG Fc receptors (FcgRs). Systemic inflammation induced by LPS further increased protein levels of the activating FcgRIII and FcgRIV, but not of other microglial receptors, including the inhibitory FcgRII. In addition to these changes in receptor expression, IgG levels in the brain parenchyma were increased during chronic neurodegeneration, and these IgG levels further increased after systemic inflammation. g Chain–deficient mice show modified proinflammatory cytokine expression in the brain after systemic inflammation. We conclude that systemic inflammation during chronic neurodegeneration increases the expression levels of activating FcgR on microglia and thereby lowers the signaling threshold for Ab-mediated cell activation. At the same time, IgG influx into the brain could provide a cross linking ligand resulting in excessive microglia activation that is detrimental to neurons already under threat by misfolded protein
CD20-induced lymphoma cell death is independent of both caspases and its redistribution into Triton X-100 insoluble membrane rafts
No full textRituximab is routinely used for the treatment of neoplasia, although the mechanism of action remains uncertain. In the current study, CD20-induced apoptosis was investigated with a panel of anti-CD20 monoclonal antibodies (mAb) in a wide range of cell lines. A hierarchy of mAb activity was apparent, with the B1 mAb generally the most potent. Apoptosis through CD20 was dependent on the nature of mAb binding and correlated with the extent of homotypic cell adhesion induced. However, using anti-CD20 mAb, which vary in the extent to which they redistribute wild-type and mutant CD20 molecules to membrane rafts, we showed that CD20-induced apoptosis was independent of translocation to TX-100 insoluble rafts. Using crmA-transfected cells and caspase inhibitors, we showed that phosphatidylserine translocation and mitochondrial permeability transition evoked during CD20-induced apoptosis appeared caspase independent. Furthermore, in cytoplasts which lack mitochondria and in Bcl2-transfected cells, phosphatidylserine was still translocated to the cell surface after CD20 stimulation. Together, these data imply that CD20 can evoke apoptosis without the involvement of mitochondria and caspases and irrespective of redistribution into TX-100 insoluble membrane rafts.<br/
CD40 ligation for immunotherapy of solid tumours
No full textTumour vaccines provide an important focus of current cancer research and are often based on the premise that although T-cells do respond naturally to certain tumours, this is usually weak and therefore ineffective at controlling disease. An integral and necessary part of a T-cell immune response involves triggering of CD40 on antigen-presenting cells (APC) by its ligand, CD154, on responding T helper (Th) cells. Furthermore, cytotoxic responses to tumours may fail because the Th-cell response is inadequate and unable to provide CD40 stimulation of APC. Growing evidence shows that stimulating APC with soluble CD40L or an agonistic anti-CD40 mAb can, at least in part, replace the need for Th cells and generate APC that are capable of priming cytotoxic T lymphocytes (CTL). The aim of this study was to investigate whether a range of solid tumours (CD40?) could be treated with anti-CD40 mAb. It was found that this treatment was effective, and correlated with the intrinsic immunogenicity and aggressiveness of the tumours. The mAb could be delivered locally or at a distal site, but increased antigen load provided by irradiated tumour cells added little to the effectiveness of the treatment. T-cells were required since cytokine (interferon-?) and CTL activity were demonstrated following treatment and the therapeutic efficacy was lost in nude mice. In addition, depletion of CD8+ cells abrogated protection whilst depletion of CD4+ cells had no effect. This study demonstrates that solid CD40? tumours are sensitive to anti-CD40 mAb therapy and that the response bypasses the need for Th cells
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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