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C Pohl

Publications and source records attributed to C Pohl.

At least 37 records · Page 2Linked to original sources
PubMed1999

Characterization of a chimeric T-cell receptor with specificity for the Hodgkin's lymphoma-associated CD30 antigen.

Recombinant receptors with antibody-like specificity for tumor-associated antigens were shown to direct specifically T cells to target tumor cells. Hodgkin and Reed-Sternberg cells, the malignant cell population in Hodgkin's lymphoma, express high amounts of the cell surface antigen CD30. An anti-CD30 T-cell receptor with cellular activation properties is expected to graft T cells with specificity to Hodgkin cells. Here, the authors characterize a chimeric T-cell receptor with an extracellular domain consisting of the single-chain antibody fragment HRS3-scFv with specificity for the CD30 antigen and intracellular domain of the signal transducing part of the Fc-epsilon-I-gamma receptor. The HRS3-scFv was derived from the monoclonal anti-CD30 antibody HRS3 and retained specificity for the CD30 antigen. The recombinant HRS3-scFv-gamma receptor was expressed under control of the RSV-LTR after transfection into MD45 T-cells. The chimeric receptor protein is detected and analyzed by enzyme-linked immunosorbent assay (ELISA) and immunoprecipitation. Expression of the chimeric receptor converts MD45 T cells to specificity for CD30+ lymphoma cells. Specific cross-linking of the chimeric receptor with antigen resulted in cytolytic reactivity against CD30+ tumor cells in vitro. The results demonstrate that the chimeric receptor HRS3-scFv-gamma converts T cells to a specific MHC-unrestricted cytolytic response against CD30+ tumor cells offering an alternative strategy in cellular immunotherapy of Hodgkin's disease.

Animals↗
PubMed1999

Anti-TNF antibody in Crohn's disease--status of information, comments and recommendations of an international working group.

The chimeric anti-TNF antibody Remicade (Infliximab) has recently been approved for human use by the FDA and is now available on the market. Since there is considerable interest in this kind of treatment among patients with Crohn's disease, an international working group has summarized the presently available information about efficacy, side effects and possible problems of this treatment. Studies show that Remicade is effective in the treatment of active Crohn's disease, maintaining remission and fistulae. The working group does not see Infliximab as a first-line treatment for Crohn's disease. It may be used in active phase recurrent disease, chronic active disease and fistulae if standard treatment was not successful. For the surveillance special attention has to be given to the unknown malignancy rate of Infliximab. Infusion should be performed in an institution, routinely performing intravenous infusions and a two-hour surveillance of the patients should be guaranteed to recognize anaphylactic reactions or acute side effects. There is presently no information indication that the combination with immunosuppressants might increase risks or side effects of this treatment. Due to the limited information available the working group would prefer to use Remicade in studies only and recommends central collection and documentation of all data on efficacy and side effects for the next year.

Antibodies, Monoclonal↗
PubMed1998

Protein variant separations by cation-exchange chromatography on tentacle-type polymeric stationary phases.

We developed a set of prototype cation-exchange column packings that are based on a hydrophilic coated, pellicular polymeric support with a grafted tentacular surface chemistry that is highly suited to resolving closely related protein variants. These column packings (1) afford minimal band spreading in conjunction with extremely high selectivity, (2) exhibit a very hydrophilic character and (3) have moderate loading capacity. Cytochrome c variants (bovine, horse, rabbit) were baseline-separated, as was native ribonuclease A and its two deamidation products, the Asp67 and isoAsp67 forms. Humanized monoclonal antibody variants differing in the presence of lysine at the C terminus of the heavy chains were baseline-resolved. Finally, the separation of hemoglobin variants found in a sample containing elevated levels of glycated hemoglobin was also demonstrated.

Amides↗
PubMed1998

Isolation of single chain antibody fragments with specificity for cell surface antigens by phage display utilizing internal image anti-idiotypic antibodies.

Recombinant single chain antibody fragments (scFv) with specificity for membrane-bound antigens can be isolated by phage display techniques. The strategy involves selection of recombinant phage antibodies by binding to cells expressing the respective antigen. This results frequently in high nonspecific adherence of phages to cellular membranes. To resolve the problem we have made use of an internal image anti-idiotypic antibody mimicking the membrane-bound CD30 antigen and successfully isolated scFv fragments with specificity for CD30. The cDNA coding for the immunoglobulin heavy and light chain variable regions of the anti-CD30 monoclonal antibody (mAb) HRS3 was expressed by phage display techniques. Recombinant HRS3-scFv phages were efficiently enriched by one cycle of panning on the internal image anti-idiotypic mAb 9G10. The isolated HRS3-scFv clone retained the binding specificity of the parental mAb HRS3 to the internal image anti-idiotypic mAb 9G10 as well as to an anti-idiotypic mAb without the internal image. Furthermore HRS3-scFv reacted with recombinant and cell-bound CD30 antigen, respectively. Binding of scFv fragments to anti-idiotypic mAbs will provide a versatile strategy for the efficient isolation of recombinant antibody fragments.

Antibodies, Anti-Idiotypic↗
PubMed1998

An anti-CD30 chimeric receptor that mediates CD3-zeta-independent T-cell activation against Hodgkin's lymphoma cells in the presence of soluble CD30.

Hodgkin's lymphoma patients fail to establish an efficient cellular response against CD30+ Hodgkin/Reed-Sternberg cells. An impaired T-cell receptor/CD3-zeta-mediated activation of T cells is thought to be involved in this situation. We here present a chimeric anti-CD30 receptor that mediates MHC and T-cell receptor/CD3-zeta-independent T-cell activation against CD30+ lymphoma cells even in the presence of soluble CD30. The receptor consists of the binding domain of the monoclonal antibody HRS3 and the signaling unit of the Fc epsilonRI-receptor gamma-chain. After expression in MD45 T cells, receptor cross-linking with immobilized anti-idiotypic monoclonal antibody and CD30+ cells, respectively, results in increased interleukin 2 secretion and specific cytolysis of CD30+ Hodgkin's lymphoma cells. Soluble CD30 in concentrations up to 6000 units/ml did not interfere with cellular activation induced by membrane-bound antigen. This demonstrates the feasibility of the chimeric anti-CD30-scFv-gamma receptor in CD30+ lymphoma cell targeting, even in the presence of as high concentrations of soluble CD30 as are found in patients during progression of the disease.

CD3 Complex↗
PubMed1998

Proton magnetic resonance spectroscopy of the primary motor cortex in patients with motor neuron disease: subgroup analysis and follow-up measurements.

OBJECTIVES: To determine the motor cortex degeneration in patients with amyotrophic lateral sclerosis (ALS) using proton magnetic resonance spectroscopy, and to prove that proton magnetic resonance spectroscopy is suited to monitor the course of disease with follow-up examinations. MATERIALS AND METHODS: We studied 33 patients with ALS whose conditions were diagnosed according to the El Escorial World Federation of Neurology criteria. Nine patients with ALS were followed up for up to 2 years. The control group included 20 healthy volunteers and 4 patients with multifocal motor neuropathy. Proton magnetic resonance spectroscopy determined levels of the brain metabolites N-acetylaspartate (NAA), choline, inositol-containing compounds, glutamate/glutamine, and phosphocreatine. RESULTS: Patients with ALS showed a significant reduction in the NAA-choline (P <.001) and NAA-phosphocreatine (P <.005) metabolite ratios and significantly elevated choline-phosphocreatine (P <.005) ratios compared with controls. Inositol-phosphocreatine ratios were also elevated in case patients, but the increase was less pronounced (P <.05). No differences in glutamate/glutamine-phosphocreatine ratios were detected between case patients and controls. An analysis of subgroups demonstrated less significant differences in NAA-choline metabolite ratios (P<.05), even in patients with pure lower motor neuron syndrome (suspected ALS). No changes in metabolite T1 and T2 relaxation times were observed. Patients with multifocal motor neuropathy showed normal metabolic ratios. Progressive alterations in affected metabolite ratios could be documented in the follow-up examinations. CONCLUSIONS: Spectroscopic changes in the motor cortices of patients with ALS correspond with a reduction in levels of NAA and an elevation in levels of choline and inositol compounds. Since NAA is exclusively expressed in neurons, the observed decrease of NAA reflects neuronal loss or dysfunction. Inositol and choline are associated with plasma membrane metabolism, so the release of these compounds may be related to membrane disorders.

Adult↗
PubMed1998

High-resolution emboli detection and differentiation by characteristic postembolic spectral patterns.

BACKGROUND AND PURPOSE: High-intensity transient signals (HITS) detected by transcranial Doppler ultrasonography correspond to microemboli in intracranial arteries. The purpose of this study was to develop new diagnostic criteria for the differentiation of these microembolic signals from artifact, based on a high-resolution analysis of Doppler power spectra in an in vitro model. METHODS: Two hundred seventy-six formed emboli, consisting of different biological and nonbiological materials and as air bubbles, were injected into a flow phantom with artificial blood vessels and perfused in a steady or a pulsatile way. Embolic passage was assessed with a modified 2.5-MHz pulsed Duplex machine and a commercial 2-MHz Doppler system. Embolic HITS were analyzed using internationally accepted criteria for the audiovisual characteristics of HITS. Doppler spectra changes associated with HITS were evaluated by means of a specially developed high-resolution analysis of Doppler raw data. RESULTS: Seventy-seven percent of all embolic events could be identified using conventional audiovisual criteria for embolic HITS. Analysis of Doppler spectra showed that all injected emboli generated high-amplitude signals with a minimum of at least 3 dB above background level. In addition, using high-resolution processing, specific changes in Doppler spectral patterns could be identified after all embolic HITS caused by solid particles. These postembolic spectral patterns were always characterized by a Doppler frequency shift decreasing in time and resembling the letter lambda (lambda). Duration and appearance of the postembolic spectral patterns were mainly influenced by the size and velocity of the embolus. Similar phenomena could not be found in case of embolism by either small air bubbles or in case of provoked artifact registration. Using a commercial Doppler system specific, we documented postembolic spectral patterns in 47% of injected emboli. CONCLUSIONS: In this study, highly specific changes in Doppler spectral patterns associated with microembolic HITS could be characterized, resulting in further criteria for the differentiation between microembolic signals and artifact in Doppler emboli detection. The sensitivity of the detection of these signals can be increased by high-resolution analysis of raw Doppler data.

Animals↗
PubMed1998

Chimeric anti-TAG72 receptors with immunoglobulin constant Fc domains and gamma or zeta signalling chains.

We recently described the generation and expression of a chimeric T cell receptor with specificity for the tumor antigen TAG72 consisting of the single chain antibody (scFv) B72.3-scFv and the gamma chain of the FcepsilonRI receptor. The corresponding chimeric receptor containing the zeta chain of the TCR as signalling unit is not functionally expressed reflecting that the requirements for functional expression of chimeric receptors containing the gamma signalling chain are apparently different compared to those containing the CD3zeta signalling chain of the TCR. We describe a novel set of chimeric anti-TAG72 receptors including in their extracellular moiety the constant immunoglobulin CH2/3 domains that allow stable expression of chimeric gamma as well as zeta receptors. We designed anti-TAG72 receptors that consist of a scFv fragment derived from an anti-TAG72 second generation antibody (CC49) and of the CH2/3 domains of the human IgG and intracellularily either of the zeta or gamma signalling chain. The recombinant CC49-CH2/3-zeta and CC49-CH2/3-gamma DNA, respectively, was transfected into MD45 T cells and expressed under control of the RSV LTR. Both receptors were found on the cell membrane of transfected cells as demonstrated by flow cytometry analysis using an anti-human IgG Fc antibody directed to the CH2/3 immunoglobulin domains of the chimeric receptor. Specific cross-linking of the chimeric zeta as well as the gamma receptor by antigen or anti-human Ig antibodies resulted in specific activation of transfected cells. Our results demonstrate that both the gamma chain and the zeta chain++ containing receptor are stably expressed and convert T cells to specificity for the TAG72 antigen. This receptor design will facilitate efficient generation of genetically modified peripheral T cells and may provide valuable tools for the cellular immunotherapy of TAG72+ tumors.

Animals↗
PubMed1998

Generation of the single chain antibody fragment conserves the idiotypic profile of the anti-CD30 monoclonal antibody HRS3.

Recombinant single chain antibody fragments (scFv) derived by combining immunoglobulin VL and VH regions provide valuable antibody-like reagents. A number of them are shown to have retained the antigen specificity of the parental monoclonal antibody (MoAb). Little is known about the idiotypic profile of scFv fragments compared with that of the parental MoAb. To address this question we analysed the idiotypic profile of a scFv that was derived by phage-display techniques from the anti-CD30 MoAb HRS3. We assayed (i) binding of HRS3-scFv to recombinant CD30-Fc antigen and to four different anti-idiotypic MoAbs defining at least three different idiotopes on HRS3, and (ii) cross-competition with the parental MoAb HRS3 and the closely related anti-CD30 MoAb HRS4. The assays revealed that the HRS3-scFv fragment exhibits the same specificity for both CD30 antigen and the tested anti-idiotypic MoAbs compared with the parental MoAb demonstrating that the recombinant scFv fragment has retained the complete idiotope of the parental MoAb.

Animals↗
PubMed1997

The low-dose monoethylglycinexylidide test: assessment of liver function with fewer side effects.

The hepatic metabolism of lidocaine (1 mg/kg intravenously) to its metabolite monoethylglycinexylidide (MEG-X) is the basis of the standard MEG-X test. To reduce the lidocaine-induced side effects, we evaluated the MEG-X formation after 0.5 and 1 mg/kg lidocaine intravenously in subjects with normal (n = 5) and severely impaired liver function (n = 7) (study I). From this study, a low-dose test (MEG-X concentration 30 minutes after 50 mg lidocaine intravenously [MEG-X30min] normalized to standard MEG-X test results) was developed. Sensory side effects from this low dose and from the standard MEG-X test were compared in a double-blind, randomized, cross-over study (study II) comprising 15 individuals with normal liver function and 45 patients with cirrhosis (15 Child A, 15 Child B, and 15 Child C). In study I, MEG-X formation rate was dose-independent in patients with severely impaired liver function. In study II, normalized MEG-X test results (ranging from < or = 4 to 120 microg/L) were virtually identical to the standard test results (mean difference: -1.9 microg/L; 95% confidence interval [CI]: -5.3; 1.5 microg/L). Fewer individuals experienced side effects (30% vs. 53%) with the low-dose test (P = .0013). In a multivariate analysis, the Child-Pugh score was inversely related to the occurrence of side effects. The low-dose MEG-X test gives almost identical results to the standard MEG-X test and is associated with fewer side effects, which occur less often in individuals with more severely compromised liver function.

Adult↗
PubMed1997

Specific activation of resting T cells against tumour cells by bispecific antibodies and CD28-mediated costimulation is accompanied by Th1 differentiation and recruitment of MHC-independent cytotoxicity.

Specific activation of resting lymphocytes for tumour targeting can be achieved by bispecific monoclonal antibodies (bi-MoAbs) with specificity for tumour antigens and T cell-activating antigens in combination with a costimulatory anti-CD28 antibody. In this study we focus on the immunomodulatory function of an anti-CD3/CA19-9 bi-MoAb in combination with a costimulatory anti-CD28 antibody which may result not only in antigen-specific, T cell-mediated tumour cell lysis but also in recruitment of other cellular effector functions. In combination with costimulatory anti-CD28 antibodies, resting peripheral lymphocytes could be activated specifically to secrete high amounts of Th1 cytokines (IL-2, interferon-gamma (IFN-gamma)) characterizing a cellular immune response. In contrast, no IL-4 and only low amounts of IL-10 could be detected. Furthermore, bi-MoAb-mediated CA19-9-specific activation of T cells was accompanied by recruitment of MHC- and CA19-9-independent cytotoxicity, as was determined by lysis of different CA19-9-cell lines. This MHC-independent cytotxicity was mediated at least in part by activated natural killer (NK) cells, as depletion of CD16+ NK cells resulted in substantial decrease of cytotoxicity against CA19-9- targets. Our results indicate that specific activation of resting T cells with CD3-associated bi-MoAbs in combination with an anti-CD28 antibody leads to a Th1 differentiation pathway and is accompanied by recruitment of MHC-independent lymphokine-activated killer (LAK) cell cytotoxicity which can possibly be directed against a heterogeneous tumour.

Antibodies, Bispecific↗
PubMed1997

T cell targeting of TAG72+ tumor cells by a chimeric receptor with antibody-like specificity for a carbohydrate epitope.

BACKGROUND & AIMS: Chimeric receptors with specificity for defined tumor antigens are valuable tools for targeting cytolytic T cells specifically to tumor cells. The aim of this study, for the situation of gastrointestinal cancer, was to investigate the generation of a chimeric T cell receptor that specifically binds the tumor antigen TAG72 (CA72-4) and transmits a signal for cellular activation. METHODS: A single-chain antibody (scFv) was derived from the monoclonal anti-TAG72 antibody B72.3 by phage display techniques (B72.3-scFv) and fused to the signaling unit of the Fc epsilon-RI receptor gamma chain, resulting in a chimeric signaling receptor, B72.3-scFv-gamma. RESULTS: The B72.3-scFv and the chimeric B72.3-scFv-gamma receptor bound specifically to the TAG72 antigen. After transfection, T cells expressing the chimeric B72.3-scFv-gamma specifically recognized TAG72 positive cells. Cross-linking of the chimeric receptor with antigen resulted in interleukin 2 release and cytolytic activity against TAG72 positive tumor cells in vitro. CONCLUSIONS: T cells equipped with the chimeric anti-TAG72 receptor can be specifically activated to target and lyse TAG72 positive gastrointestinal tumor cells.

Animals↗
PubMed1997

A prospective evaluation of the diagnostic work-up before laparoscopic cholecystectomy.

BACKGROUND AND STUDY AIMS: A prerequisite for successful laparoscopic cholecystectomy is the exclusion of potential risks such as cholangiolithiasis or anatomical malformations. As there is no general agreement regarding the appropriate preoperative diagnostic work-up, a comparative study of different diagnostic methods was carried out. PATIENTS AND METHODS: In 180 consecutive patients admitted to a community hospital for cholecystectomy due to symptomatic cholecystolithiasis, a prospective comparison was carried out of the diagnostic accuracy of patient history, physical examination, laboratory tests, upper gastrointestinal endoscopy, intravenous cholangiography, ultrasonography, and endoscopic retrograde cholangiopancreatography (ERCP). RESULTS: Measurement of the diameter of the common bile duct was found to be a reliable method as a single noninvasive parameter for diagnosing cholangiolithiasis (sensitivity 100%, specificity 93%), with good predictive power (positive predictive value 0.7, negative predictive value 1.0). The best accuracy achieved noninvasively and without sonography was with a combination of positive patient history and gamma-glutamyl transferase findings (sensitivity 58%, specificity 84%, positive predictive value 0.37, negative predictive value 0.93). ERCP detected additional cholangiolithiasis in 19 of 139 patients (13.7%) and anatomical malformations in three patients. In all 19 patients, the bile ducts were cleared of stones endoscopically within 24 hours, prior to laparoscopic cholecystectomy. Among the 163 patients primarily assigned to laparoscopic cholecystectomy, the protocol diagnostic work-up, including ERCP, allocated three patients (1.8%) to open surgery. Conversion from laparoscopic cholecystectomy to open cholecystectomy occurred in a further two of 158 patients (1.3%). CONCLUSIONS: These results show that routine ultrasonography prior to laparoscopic cholecystectomy can be recommended in order to determine the diameter of the common bile duct. In patients with a ductal diameter of more than 6 mm, ERCP should be performed. Laparoscopic cholecystectomy can be carried out within 24 hours after ERCP and papillotomy.

Adolescent↗
PubMed1997

Specific activation of resting T cells against CA19-9+ tumor cells by an anti-CD3/CA19-9 bispecific antibody in combination with a costimulatory anti-CD28 antibody.

Specific activation of resting lymphocytes for tumor targeting can be achieved by bispecific monoclonal antibodies (bi-mAb) with specificity for tumor antigens and T-cell-activating antigens, respectively, in combination with a costimulatory anti-CD28 antibody. We describe the generation and function of a bi-mAb with specificity for CD3 and for the tumor antigen CA19-9. The bi-mAb OKT3/NSI19-9 was generated by somatic fusion of two hybridoma lines secreting antibodies against CA19-9 and CD3, respectively. A hybrid/hybridoma was established, and its bi-mAb was characterized. In combination with a costimulatory anti-CD28 mAb resting peripheral lymphocytes could be activated specifically with T-cell proliferation and secretion of high amounts of interferon-gamma. On specific T-cell activation, bi-mAb OKT3/NSI19-9 could also redirect the cytotoxic effects of these T cells toward CA19-9+ tumor cells in vitro. Our results indicate that specific activation of resting T cells with bi-mAb OKT3/NSI19-9 in combination with an anti-CD28 mAb can activate resting T cells specifically and leads to antigen-dependent bi-mAb-mediated cytotoxicity against CA19-9+ target cells. This approach may offer new perspectives for the specific immunotherapy of CA19-9+ tumors.

Antibodies, Bispecific↗