Inhibition of platelet adhesion to collagen by monoclonal anti-CD36 antibodies

Monoclonal anti CD36 antibodies capable of inhibiting platelet adhesion to collagen have not previously been identified. We have now prepared two groups of monoclonal antibodies. One group was prepared using, as immunogen, highly purified (99+%) CD36 prepared by a denaturing procedure. These antibodies (Mo series) reacted strongly with CD36 on protein blots but did not immunoprecipitate native CD36 from platelet lysates nor inhibit platelet adhesion to collagen. The second group of monoclonal antibodies (131 series) was prepared using CD36 purified to >95% by a non-denaturing procedure. These antibodies reacted with control platelets, but not Nak^a-negative platelets which lack CD36, as measured by flow cytometry and by immunoprecipitation. Three monoclonal antibodies of this latter group (131.4, 131.5 and 131.7) inhibited platelet adhesion to collagen in static systems under Mg²⁺-independent conditions but had little effect in the presence of Mg²⁺. 131.4 and 131.7 also inhibited adhesion to collagen using citrated whole blood in a parallel plate flow chamber at physiological shear rates (800 s⁻¹), whereas 131.5 was without effect. These are the first anti-CD36 monoclonal antibodies shown to be capable of inhibiting platelet adhesion to collagen and provide further evidence that CD36 plays a role in platelet–collagen interaction.     

Inhibition of platelet adhesion to collagen by monoclonal anti-CD36 antibodies

Monoclonal anti CD36 antibodies capable of inhibiting platelet adhesion to collagen have not previously been identified. We have now prepared two groups of monoclonal antibodies. One group was prepared using, as immunogen, highly purified (99+%) CD36 prepared by a denaturing procedure. These antibodies (Mo series) reacted strongly with CD36 on protein blots but did not immunoprecipitate native CD36 from platelet lysates nor inhibit platelet adhesion to collagen. The second group of monoclonal antibodies (131 series) was prepared using CD36 purified to >95% by a non-denaturing procedure. These antibodies reacted with control platelets, but not Nak^a-negative platelets which lack CD36, as measured by flow cytometry and by immunoprecipitation. Three monoclonal antibodies of this latter group (131.4, 131.5 and 131.7) inhibited platelet adhesion to collagen in static systems under Mg²⁺-independent conditions but had little effect in the presence of Mg²⁺. 131.4 and 131.7 also inhibited adhesion to collagen using citrated whole blood in a parallel plate flow chamber at physiological shear rates (800 s^?1), whereas 131.5 was without effect. These are the first anti-CD36 monoclonal antibodies shown to be capable of inhibiting platelet adhesion to collagen and provide further evidence that CD36 plays a role in platelet–collagen interaction.     

Platelet activation induced by a murine monoclonal antibody directed against a novel tetra-span antigen

MAb 14A2.H1 identifies a novel low-abundance platelet surface antigen, PETA-3, which is a member of the tetra-span (TM4) family. This MAb brings about platelet aggregation and mediator release, which is completely inhibitable by prostaglandin E₁, and partially inhibitable by aspirin and ketanserin. Platelet activation by MAb 14A2.H1 is dependent on interaction with both the platelet Fc receptor, FcγRII, and the specific antigen as it was prevented by either a blocking MAb to FcγRII (IV.3) or F(ab')₂ fragments of 14A2.H1. The extent of platelet activation by the antibody varied considerably between donors, and is believed to reflect the polymorphism of FcγRII. Subaggregating concentrations of 14A2.H1 synergized with other platelet agonists, ADP, adrenaline, collagen and serotonin, indicating signalling via a pathway distinct from these activators. Synergy was also blocked by MAb rv.3, or F(ab')₂ fragments of 14A2.H1. The similar low copy number of PETA-3 and FcγRII in the platelet membrane (approximately 1000/platelet). together with the dependence on FcγRII for activation by MAb 14A2.H1, suggests that PETA-3 may be a component of the FcγRII signal transducing complex in platelets.     

Platelet activation by immobilized monoclonal antibody: evidence for a CD9 proximal signal.

Anti-CD9 monoclonal antibodies (MoAbs) are reported to activate human platelets through stimulation of the Fc gamma II receptor. We show here that nonstimulatory F(ab')2 fragments of the anti-CD9 MoAb 50H.19 induce dense-granule release and dose-dependent platelet aggregation when attached to polystyrene latex beads. Cross-linking F(ab')2 fragments of MoAb 50H.19 by F(ab')2 fragments of goat anti-mouse IgG does not result in platelet aggregation unless the second antibody is bound to latex beads, indicating that immobilization, and not cross-linking of the stimulus, is critical to the initiation of the CD9 signal. In contrast, F(ab')2 fragments of the second antibody readily induce the aggregation of platelets treated with the anti-Fc gamma II receptor MoAb IV.3. Immobilization of MoAb per se is insufficient to induce an activation signal because intact and F(ab')2 fragments of nonstimulatory MoAb directed to glycoprotein Ib and HLA class I do not become stimulatory when attached to beads. CD9-induced activation requires cytoskeletal rearrangement because it is inhibited by cytochalasin B. Aggregation is blocked by inhibitors of the thromboxane pathway, indicating that CD9 activates phospholipase C indirectly through prior activation of phospholipase A2.     

Enhancement of T cell activation by immobilized hu5C8 (anti-CD40L) monoclonal antibody

Background: Soluble monoclonal antibodies (MoAb) targeting CD40L on T cells can partially block T cell alloreactivity by preventing the costimulatory signal of antigen presenting cells through CD40. However, it is not known if these MoAbs can also deliver inhibiting or stimulating signals through the CD40L receptor. Materials and methods: Blood mononuclear cells were stimulated by mitogens or allogeneic stimulator cells in the presence of hu5C8 MoAb, either in soluble form, or immobilized to the culture wells. T cell responses were evaluated by means of primary and secondary mixed lymphocyte culture (MLC), cytotoxic T lymphocyte (CTL) generation, immunophenotype, apoptosis assay and cytokine release. Also, the effect of hu5C8 on cells inhibited by CTLA4‐Ig was tested. Results: While the soluble hu5C8 inhibited T cell proliferation, the immobilized hu5C8 enhanced both mitogen and alloantigen‐induced proliferative and cytotoxic T cell responses, without inducing further apoptotic T cell death. In the presence of CTLA4‐Ig, immobilized hu5C8 increased the residual CD28‐independent proliferation of alloantigen‐specific T cells both in primary and secondary MLC, and prevented the inhibiting effect of CTLA4‐Ig on the generation of CTL. Immobilized hu5C8 MoAb‐stimulated T cells also showed a limited capacity of producing interleukin (IL)‐10, even in the presence of CTLA4‐Ig. Conclusions: We show that the hu5C8 MoAb has a strong mitogenic activity when immobilized, likely due to higher crosslinking capacity as compared to the soluble antibody. Strategies to induce ex‐vivo T cell responses against tumor or viral antigens by means of hu5C8 MoAb antibody will be exploited based on these findings.     

Natural anti-oxLDL IgM monoclonal antibody in the pathogenesis of atherosclerosis

Objective To explore the role and the possible molecular mechanisms of natural anti-oxLDL IgM monoclonal antibody played and involved in pathogenesis of atherosclerosis. Methods Natural anti-oxLDL IgM monoclonal antibody 3A6 was generated by using standard hybridoma production techniques. Influence of 3A6 on formation of foam cells was observed by Oil Red O staining and affinity of Na125I-conjugated oxLDL on the naive and LPS-activated macrophages. After LPS stimulation on macrophages, anti-TLR4 neutralizing mAb, p38MAPK specific inhibitor SB203580, NF-kB specific inhibitor PDTC or RNAi targeting Fcα/μ receptor (Fcamr) were applied, respectively. Results Natural anti-oxLDL IgM monoclonal antibody 3 A6 were found specifically inhibit the binding of CuoxLDL to naive macrophages but not the binding of CuoxLDL to LPS-activated macrophages. It also promoted the formation of CuoxLDL-mediated foam macrophages. 3A6 F(ab')2 or pre-incubation with un-related IgM inhibited the binding of 3A6/CuoxLDL complex to LPS-activated macrophages. LPS up-regulated the expression of Fcamr in macrophages in a dose- and time-dependent manner, which was attenuated by treatment with anti-TLR4. LPS induced the phosphorylation of p38MAPK and translocation of NF-kB p65, contributing to the up-regulated expression of Fcα/μ receptor in macrophages. Conclusions Natural anti-oxLDL IgM monoclonal antibody 3A6 specifically inhibited the binding of CuoxLDL to naive macrophages in vitro. However, LPS, through the Toll-like receptor (TLR)4 receptor, activated the p38MAPK and NF-kB pathways and up-regulated the expression of Fcα/μ receptor in macrophages, which promoted the binding of 3A6/CuoxLDL complex to macrophages through binding with Fc fragments and the formation of foam macrophages. Therefore, our findings provide a new explanation why bacterial infection deteriorates the pathogenesis of atherosclerosis.     

Treatment of rheumatoid arthritis with an anti-CD4 monoclonal antibody

The effect of treatment with a monoclonal antibody against the CD4 antigen present on T helper cells was studied in 10 patients with severe intractable rheumatoid arthritis. In an open trial, monoclonal antibody 16H5 was infused at a dosage of 0.3 mg/kg of body weight on 7 consecutive days. Studies of the kinetics demonstrated a drastic depletion of CD4+ cells, to as low as 25 cells/microliters, 1 hour after the first infusion. The subsequent recovery of the CD4+ cell numbers 24 hours after infusion did not reach initial levels, and after the full 7-day treatment cycle there was a significant reduction of the number of CD4+ cells (mean +/- SD 51 +/- 28%; P less than 0.02). There was a reduced or even inverse CD4:CD8 ratio, which generally persisted 3-4 weeks. Lymphocyte transformation assays demonstrated significantly reduced reactivity in 5 of the 9 patients who completed the 7-day course, whereas 4 individuals exhibited an unexpected elevation in the T cell response to mitogens and common antigens. Parallel laboratory studies showed a significant decrease in the erythrocyte sedimentation rate (P less than 0.05), rheumatoid factor titer (P less than 0.04), and total immunoglobulin values (P less than 0.01), as well as a reduction in C-reactive protein levels, in 7 of the 9 patients. Clinically, there was a significant reduction in the Ritchie articular index (P less than 0.05) and in the number of swollen joints (P less than 0.04). Adverse effects were urticaria in 2 patients, which led to withdrawal of therapy in 1 of them, and chills with fever, suggestive of a lymphokine release syndrome, in another 2 patients. Only low levels of human anti-mouse immunoglobulin antibodies developed (not exceeding 1.7 mg/liter). It was therefore possible to repeat the treatment cycle, achieving still better efficacy, in 4 of the patients (reductions in the Ritchie index and the number of swollen joints P less than 0.02). Our findings indicate that treatment with monoclonal antibodies against the CD4 antigen leads to immunomodulation which results in clinical benefits, at least during initial observation periods (up to 6 months postinfusion). However, it remains to be determined whether long-term remission can be induced with this therapeutic approach. The use of immunosuppressive therapies or repeated antibody treatments will have to be considered.     

Requirements for the promotion of allogeneic engraftment by anti-CD154 (anti-CD40L) monoclonal antibody under nonmyeloablative conditions.

The promotion of alloengraftment in the absence of global immune suppression and multiorgan toxicity is a major goal of transplantation. It is demonstrated that the infusion of a single modest bone marrow dosage in 200 cGy-irradiated recipients treated with anti-CD154 (anti-CD40L) monoclonal antibody (mAb) resulted in chimerism levels of 48%. Reducing irradiation to 100 or 50 cGy permitted 24% and 10% chimerism, respectively. In contrast, pan-T-cell depletion resulted in only transient engraftment in 200 cGy-irradiated recipients. Host CD4(+) cells were essential for alloengraftment as depletion of CD4(+) cells abrogated engraftment in anti-CD154-treated recipients. Strikingly, the depletion of CD8(+) cells did not further enhance engraftment in anti-CD154 mAb-treated recipients in a model in which rejection is mediated by both CD4(+) and CD8(+) T cells. However, anti-CD154 mAb did facilitate engraftment in a model in which only CD8(+) T cells mediate rejection. Furthermore, CD154 deletional mice irradiated with 200 cGy irradiation were not tolerant of grafts, suggesting that engraftment promotion by anti-CD154 mAb may not simply be the result of CD154:CD40 blockade. Together, these data suggest that a CD4(+) regulatory T cell may be induced by anti-CD154 mAb. In contrast to anti-CD154 mAb, anti-B7 mAb did not promote donor engraftment. Additionally, the administration of either anti-CD28 mAb or anti-CD152 (anti-CTLA-4) mAb or the use of CD28 deletional recipients abrogated engraftment in anti-CD154 mAb-treated mice, suggesting that balanced CD28/CD152:B7 interactions are required for the engraftment-promoting capacity of anti-CD154 mAb. These data have important ramifications for the design of clinical nonmyeloablative regimens based on anti-CD154 mAb administration.     

Induction of NK activity in large granular lymphocyte leukemia: activation with anti-CD3 monoclonal antibody and interleukin 2

Large granular lymphocyte (LGL) leukemia is a rare disease characterized by clonal expansion of LGL associated with chronic neutropenia, multiple auto-antibodies, and occasionally polyarthritis. We studied cell surface antigen expression and functional activity of leukemic LGL from ten such patients. Using two-color flow cytometric analysis, we found that leukemic LGL from all ten patients expressed the CD3 and HNK-1 markers, while cells from only four patients expressed IgG Fc receptors (FcR). The LGL leukemic cells had little or no NK activity (defined as MHC-nonrestricted cytotoxicity against K562 target cells); however, NK activity could be induced in leukemic LGL by in vitro treatment with as little as 0.05 microgram/mL of anti-CD3 monoclonal antibody. Cell sorting experiments demonstrated that NK activity was induced in CD3+ leukemic LGL (either CD3+, HNK-1+ or CD3+, FcR+) with anti-CD3 monoclonal antibody but not in normal CD3+, FcR- T cells. Treatment with purified interleukin 2 (IL 2) also caused direct activation of some CD3+ leukemic LGL. Despite induction with anti-CD3 MAb or IL 2, activated leukemic LGL did not proliferate or express high density IL 2 receptors detectable by cell sorter analysis. Treatment with alpha interferon had minimal effect on NK activity of LGL leukemic cells. These results suggest that leukemic LGL may provide a useful model for examining the signals required for LGL maturation and activation.     

Growth inhibition of experimental glioma grafts by monoclonal antibody treatment

Summary The effects of 14AC1 monoclonal antibody (McAb) on 79FR-G-41 rat glioma cells in vitro, on the formation of metastases in lung by antibody coated glioma cells, and on the growth of glioma grafts in BALB/c-nu/nu mice were investigated.The 14AC1 antibodies — isotyped as IgG2a — were obtained from a hybridoma clone established after fusion of X63-Ag8.653 myeloma cells and spleen cells of BALB/c mice hyperimmunized with 79FR-G-41 glioma cells. Antibody treatment of glioma cells in vitro caused evident cell surface alterations and pronounced growth depression of most cells. However, a few tumor cells remained unchanged in morphology and continued to proliferate. Moreover, 14AC1 antibodies drastically reduced lung metastasis by pretreated and i.v. delivered glioma cells. Additionally, 14AC1 antibodies suppressed the growth of transplanted rat gliomas in nude mice as evidenced by a longer latency period and a smaller volume of glioma grafts in treated than in control tumor bearers. Nevertheless, glioma grafts showed accelerated growth after termination of antibody treatment.Further experimental investigation is required in order to identify the precise mechanisms of the effects of McAbs on tumor cells in vitro and in vivo.     

Treatment of cutaneous T-cell lymphoma with chimeric anti-CD4 monoclonal antibody

Chimeric anti-CD4 monoclonal antibody was administered intravenously as a single dose to eight patients with mycosis fungoides. The dose was escalated throughout the study between patients groups, and individual patients received 50, 100, or 200 mg per dose. Seven of eight patients responded to treatment with an average freedom from progression of 25 weeks (range, 6 to 52 weeks). The treatment was well tolerated, and there was no clinical evidence of immunosuppression. Following treatment, there was significant suppression of peripheral blood CD4 counts in all patients for 1 to 22+ weeks. Only one patient made a very low titer human antichimeric antibody response. All but two patients made primary antibody and T-cell proliferative responses to a foreign antigen administered 24 hours after antibody infusion. However, there was generally marked, but temporary suppression of T-cell proliferative responses in vitro to phytohemagglutinin (PHA), tetanus toxoid, and normal donor lymphocytes. We conclude that at the dose levels studied, this antibody (1) had clinical efficacy against mycosis fungoides; (2) was well tolerated; (3) had a low level of immunogenicity; (4) decreased T-cell proliferative responses in vitro, and (5) did not induce tolerance to a foreign antigen.     

Therapeutic use of monoclonal anti-CD4 antibody in rheumatoid arthritis.

Ten patients with severe rheumatoid arthritis were treated with a murine monoclonal anti-CD4 (B-F5) antibody in an open study (one with 10 mg/day, 2 with 15 mg/day, 7 with 20 mg/day) for 10 consecutive days. Tolerance was excellent. All patients improved during treatment clinically (Ritchie's index, morning stiffness, pain scale) (p = 0.005), as well as biologically C-reactive protein (p = 0.008) with an average 60% reduction of each of these variables at Day 15, and clinical benefit lasted over 6 months in some patients. No significative depletion was noted in total lymphocyte or CD3, CD4, CD8, CD20, positive cells after treatment. Evidence of murine immunization was found in only 2 patients.     

Successful treatment of B-cell prolymphocytic leukemia with monoclonal anti-CD20 antibody

We report a patient with B-cell prolymphocytic leukemia (PLL) who was treated successfully with the monoclonal anti-CD20 antibody (rituximab). The patient had recurrent infections due to relative neutropenia, secondary to bone marrow infiltration. After treatment with monoclonal anti-CD20 antibodies (rituximab) 375 mg/m² weekly for 4 weeks, complete remission was obtained. It was documented by normalization of peripheral blood counts, disappearance of organomegaly, and by molecular cytogenetics-fluorescent in situ hybridization (FISH) on bone marrow cells. She remains in complete remission 8 months following the discontinuation of treatment. This is the second reported case of successful treatment of B-cell PLL with rituximab.     

抗CD34单克隆抗体标记血管生成在人脑胶质瘤组织中的表达及临床意义

应用免疫单抗标记的组织化学技术检测63例人脑胶质瘤组织中CD34的表达情况，根据CD34阳性的血管内皮细胞计数来测定肿瘤微血管密度（MVD）。结果发现，Ⅲ、Ⅳ级胶质瘤MVD显著高于Ⅰ、Ⅱ级（P＜0．05） ；术后18个月内复发和生存期＜3年者MVD显著高于术后18个月内无复发和生存期≥3年者（P＜0．10）；MVD与患者的性别、年龄、肿瘤生长部位无明显相关（P＞0．05）。认为人脑胶质瘤组织中血管形成与病理分级、术后复发及生存密切相关。可作为一项有意义的预后指标。     

Inhibition of leukocyte adherence by anti-CD18 monoclonal antibody attenuates reperfusion injury in the rabbit ear.

Tissue injury resulting from ischemia and reperfusion forms the basis of several important disorders including myocardial infarction, stroke, and circulatory shock. To examine the role of neutrophils in this process and to determine the extent to which injury is a consequence of reperfusion, we utilized the monoclonal antibody 60.3, directed to CD18, the human leukocyte adherence glycoprotein, to block intravascular neutrophil aggregation and neutrophil adherence to endothelium in a rabbit model of tissue ischemia and reperfusion. Antibody treatment either before ischemia or after ischemia, but prior to reperfusion, resulted in the same degree of significant protection against endothelial, microvascular, and tissue injury. We conclude that neutrophils and increased neutrophil adhesiveness are important in the development of microvascular and tissue injury after ischemia and reperfusion and that under these circumstances, injury is primarily a consequence of reperfusion.     

Treatment of steroid-refractory acute graft-versus-host disease with anti-CD147 monoclonal antibody ABX-CBL

ABX-CBL, an immunoglobulin M murine monoclonal antibody, recognizes CD147 and initiates cell killing through complement-mediated lysis. In a dose-finding trial, 27 patients with steroid-refractory acute graft-versus-host disease (GVHD) received ABX-CBL at 0.01 (presumed no effect dose), 0.1, 0.2, or 0.3 mg/kg per day, and an additional 32 patients were given ABX-CBL at 0.2 or 0.15 mg/kg per day. All patients had undergone allogeneic transplantation for malignant or nonmalignant disorders and received GVHD prophylaxis, generally with methotrexate- and cyclosporine-containing regimens. None responded to methylprednisolone, given for a minimum of 3 days. ABX-CBL was started 20 to 236 (median, 47) days after transplantation; it was given for 7 consecutive days and was followed by 2 infusions per week for 2 more weeks. Among 51 patients evaluable for efficacy, 26 (51%) responded, including 13 with complete responses (CR) and 13 with partial responses (PR). CR lasting 14 days or longer or PR lasting 7 days or longer occurred in 21 (41%; 8 CR, 13 PR) patients, including 19 of 43 (44%) patients who received 0.1 to 0.3 mg/kg ABX-CBL and 2 of 8 (25%) patients given 0.01 mg/kg per day. Myalgias at doses 0.2 mg/kg or greater were dose limiting and resolved without sequelae. Causes of death included organ failure, progressive GVHD, and infection. No death was attributed to ABX-CBL. At 6 months after the initiation of ABX-CBL therapy, 26 (44%) patients were surviving. These results are encouraging. Further studies on the use of ABX-CBL in the management of GVHD are warranted.