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Biomedical subjects

S Bauer

Publications and source records attributed to S Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1997

Role of naive and memory T cells in tumor cell lysis mediated by bi-specific antibodies.

Bispecific monoclonal antibodies (Bi-mAb) with specificity for a tumor associated antigen and the CD3 or CD28 antigen on T lymphocytes, respectively, induce activation of resting T lymphocytes and target-specific tumor cell lysis. Former studies had confirmed that T cells expressing the CD45RO "memory" antigen at high levels were the most potent effectors of Bi-mAb-mediated cytotoxicity when compared to their "naive" counterparts expressing the CD45RA antigen. Further analysis of the T cell subpopulations revealed that within the memory T cell pool, CD8+ T cells were the effector cell, population with strongest cytolytic activity. The cytolytic activity was correlated with the expression level of perforin and granzymes B mRNA. Ca2+ complexing agents, which abrogate perforin activity, reduced necrosis, while inhibition of granzyme activity in effector or target-cells had a similar effect on apoptosis. These results confirm the crucial role perforin and granzymes play in target-cell lysis and explain why CD8+CD45RO+ T cells activated by combined CD3 and CD28 antigen triggering represent the T cell pool with highest cytolytic potential.

Antibodies, Bispecific↗
PubMed1997

Hypericin and pseudohypericin: pharmacokinetics and effects on photosensitivity in humans.

Extracts of St. John's wort (Hypericum perforatum) are used in treatment of depression. They contain various substances with the naphthodianthrones hypericin and pseudohypericin as characteristic ingredients. These compounds were shown to cause phototoxicity in cell culture and in animals. A placebo-controlled randomized clinical trial with monitoring of hypericin and pseudohypericin plasma concentration was performed to evaluate the increase in dermal photosensitivity in humans after application of high dose hypericum extracts. The study was divided into a single dose and a multiple dose part. In the single dose period, each of 13 volunteers received in a double blind fourfold complete crossover design, either placebo, or 900, 1800 or 3600 mg of a standardized hypericum extract (LI 160) containing zero, 2.81, 5.62 and 11.25 mg of total hypericin (total hypericin is the sum of hypericin and pseudohypericin). Maximum total hypericin plasma concentrations were observed about 4 h after dosage and were 0, 0.028, 0.061 and 0.159 mg/L, respectively. Before and 4 h after drug intake, the subjects were exposed at small areas of their back to increasing doses of solar simulated irradiation (SSI, with combined ultraviolet A, UV-A, and UV-B light) and another part was exposed to selective UV-A light irradiation. Minimal erythema dose was determined 5, 20 and 68 h after irradiation. Comparison of SSI sensitivity without and with hypericum extract did not show and difference and there was no dose-related trend in light sensitivity. Sensitivity to selective UV-A light was increased only after the highest dose from a minimal tanning dose of 10.8 J/ cm2 (mean) after placebo to 8.7 J/cm2 after 3600 mg extract with marginal statistical significance (p = 0.03 by one sided paired t-test). There was no correlation between total hypericin plasma concentrations and photosensitivity. In the multiple dose part, 50 volunteers received 600 mg hypericum extract t.i.d. with a daily dose of 5.6 mg of total hypericin. Comparison of UV light sensitivity before dosing with day 15 of treatment showed a slightly increased SSI sensitivity expressed by decrease of the MED from 0.17 to 0.16 J/cm2 (p = 0.005 by Wilcoxon test), and similarly, sensitivity to UV-A light increased (the mean tanning dose decreased from 9.9 to 7.8 J/cm2, p < 0.0001). This increase in cutaneous light sensitivity could be compensated by reducing irradiation time by 21%. Doses used in this study were higher than typical doses in current commercial preparations. In spite of these high doses in the double blind single dose part, frequency of side effects was equal to placebo medication and UV light sensitivity was not or only marginally increased. The study does not, however, exclude phototoxic reactions with doses above 11.25 mg of total hypericin and plasma levels above 100 micrograms/L. Furthermore, phototoxicity may be different after application of pure hypericin, since some constituents in the plant extract may exhibit protective effects.

Adult↗
PubMed1997

Pharmacokinetics of tacrolimus (FK 506) in children and adolescents with renal transplants.

BACKGROUND: Only few data exist on pharmacokinetics of tacrolimus in children. PATIENTS: In 1995 and 1996, 14 children (mean age 13 years, range 5-23 years) received tacrolimus after renal transplantation; 10 of these after biopsy-proven steroid-resistant rejection (2 with vascular rejection), two for cyclosporin A (CsA)-induced severe nephrotoxicity, one for untreatable gingival hyperplasia on CsA, and one child was treated primarily after transplantation because of severe liver involvement in nephronophthisis. Pharmacokinetic investigations were performed after establishing a stable maintenance dose with trough levels in the desired window of 5-12 ng/ml. RESULTS: Mean follow-up time was 6 months (range 3-25 months). Eleven patients are still on tacrolimus. Two were discontinued because of severe aggravation of chronic persistent hepatitis C (one of them also developed diabetes mellitus), and one patient was subsequently switched to conventional immunosuppression because of tacrolimus-associated nephrotoxicity. All tacrolimus levels were measured by a modified assay (MEIA, Tacrolimus, Abbott) with improved sensitivity. At the time of switch, median serum creatinine was 234 +/- 82 mumol/l and 6 months after switch 201 +/- 99 mumol/l. All grafts are still functioning. Mean FK-506 dose was 0.16 mg/kg body weight/day (range 0.036-0.30 mg/kg). Mean trough level was 7.1 +/- 2.6 ng/ml in the morning and 6.5 +/- 2.0 ng/ml in the evening. Median time of maximum concentration (tmax) was 120 min after application, and the mean maximum concentration (Cmax) was 15.2 +/- 6.7 ng/ml. Mean area under the curve (AUC) was 104 +/- 33 ng* h/ml, with a range from 65 yo 169 ng* h/ml. No patient had unsatisfactorily low trough levels during the study. There was only a weak but significant (P < 0.05) correlation between dose per kg body weight and AUC and, as expected, an excellent correlation (r2 = 0.73, P < 0.001) between AUC and trough level. CONCLUSION: Because of interindividual variation between patients, therapeutic drug monitoring of tacrolimus is mandatory. In this study, a daily dose of 0.15 mg/kg was sufficient in most patients. We recommend the performance of at least one pharmacokinetic study after establishing stable FK 506 trough levels to ascertain a safe profile.

Adolescent↗
PubMed1997

Cytochrome P450 2D6 variants in a Caucasian population: allele frequencies and phenotypic consequences.

Cytochrome P450 2D6 (CYP2D6) metabolizes many important drugs. CYP2D6 activity ranges from complete deficiency to ultrafast metabolism, depending on at least 16 different known alleles. Their frequencies were determined in 589 unrelated German volunteers and correlated with enzyme activity measured by phenotyping with dextromethorphan or debrisoquine. For genotyping, nested PCR-RFLP tests from a PCR amplificate of the entire CYP2D6 gene were developed. The frequency of the CYP2D6*1 allele coding for extensive metabolizer (EM) phenotype was .364. The alleles coding for slightly (CYP2D6*2) or moderately (*9 and *10) reduced activity (intermediate metabolizer phenotype [IM]) showed frequencies of .324, .018, and .015, respectively. By use of novel PCR tests for discrimination, CYP2D6 gene duplication alleles were found with frequencies of .005 (*1x2), .013 (*2x2), and .001 (*4x2). Frequencies of alleles with complete deficiency (poor metabolizer phenotype [PM]) were .207 (*4), .020 (*3 and *5), .009 (*6), and .001 (*7, *15, and *16). The defective CYP2D6 alleles *8, *11, *12, *13, and *14 were not found. All 41 PMs (7.0%) in this sample were explained by five mutations detected by four PCR-RFLP tests, which may suffice, together with the gene duplication test, for clinical prediction of CYP2D6 capacity. Three novel variants of known CYP2D6 alleles were discovered: *1C (T1957C), *2B (additional C2558T), and *4E (additional C2938T). Analysis of variance showed significant differences in enzymatic activity measured by the dextromethorphan metabolic ratio (MR) between carriers of EM/PM (mean MR = .006) and IM/PM (mean MR = .014) alleles and between carriers of one (mean MR = .009) and two (mean MR = .003) functional alleles. The results of this study provide a solid basis for prediction of CYP2D6 capacity, as required in drug research and routine drug treatment.

Adult↗
PubMed1996

Cell stress-regulated human major histocompatibility complex class I gene expressed in gastrointestinal epithelium.

Conventional major histocompatibility complex (MHC) class I genes encode molecules that present intracellular peptide antigens to T cells. They are ubiquitously expressed and regulated by interferon gamma. Two highly divergent human MHC class I genes, MICA and MICB, are regulated by promoter heat shock elements similar to those of HSP70 genes. MICA encodes a cell surface glycoprotein, which is not associated with beta 2-microglobulin, is conformationally stable independent of conventional class I peptide ligands, and almost exclusively expressed in gastrointestinal epithelium. Thus, this MHC class I molecule may function as an indicator of cell stress and may be recognized by a subset of gut mucosal T cells in an unusual interaction.

Animals↗
PubMed1996

Isochromosome 12p and maternal loss of 1p36 in a pediatric testicular germ cell tumor.

Analysis of a pediatric germ cell tumor by conventional cytogenetic investigation and fluorescence in situ hybridization showed consistently the presence of two isochromosomes 12p, loss of the maternal band 1p36, and other numerical and structural chromosome changes. The rearrangements observed resulted mainly from breaks occurring at paracentromeric regions. This report represents the first description of i(12)(p10) in a pediatric testicular embryonal carcinoma.

Adolescent↗
PubMed1996

Homozygous rapid arylamine N-acetyltransferase (NAT2) genotype as a susceptibility factor for lung cancer.

The polymorphic arylamine N-acetyltransferase (NAT2) is supposed to be a susceptibility factor for certain malignancies. A phenotyping study in 389 lung cancer patients revealed a similar distribution of rapid and slow acetylators by the caffeine test to that in 657 reference subjects (odds ratio, 1.05; 95% confidence limits, 0.81, 1.36; not significant). A separate group of 155 lung cancer patients was studied by genotyping NAT2 and was compared with a matched reference group of 310 unrelated patients and with 278 healthy volunteers. The NAT2 genotype was characterized by PCR-RFLP at nucleotide positions 191, 282, 341, 481, 590, 803, and 857. For evaluation of nucleotide 341, a 3'-mismatch primer was used. Homozygous wild-type genotypes NAT2*4/*4 were confirmed by DNA sequencing. Genotypes for rapid acetylation amounted to 43.9% among lung cancer and 41.6% among reference patients (odds ratio, 1.10 95% confidence limits, 0.73, 1.65; not significant). Discrimination into homozygous and heterozygous carriers of allele NAT2*4 revealed a distinct over-representation of NAT2*4/*4 genotypes amid lung cancer patients (odds ratio, 2.36; 95% confidence limits, 1.05, 5.32; P = 0.018). Logistic regression analysis considering sex, age, and smoking provided an odds ratio of 3.04 (95% confidence limits, 1.37, 6.75; P = 0.003). Hence, carriers of the NAT2*4/*4 genotype, with its especially high acetylation capacity, are at significantly increased risk to lung cancer.

Acetylation↗
PubMed1996

T cells from patients with Hodgkin's disease have a defective T-cell receptor zeta chain expression that is reversible by T-cell stimulation with CD3 and CD28.

To investigate the mechanisms underlying the deficiency of T lymphocytes from patients with Hodgkin's disease, we investigated the expression of the T-cell receptor (TCR) zeta chain in patients with Hodgkin's disease. By flow cytometry using an anti-zeta chain monoclonal antibody, peripheral blood T lymphocytes from patients with untreated Hodgkin's disease were shown to express decreased levels of the TCR zeta chain. After stimulation by combined CD3 and CD28 cross-linking, T cells from Hodgkin's disease patients upregulated zeta chain protein expression to normal values within 48 hours and achieved a cytolytic potential and levels of interleukin (IL)-2 secretion that were not different from T cells obtained from healthy controls. These results show that downregulation of the TCR zeta chain in Hodgkin's T lymphocytes is a reversible event. Costimulation of CD3 and CD28 is a novel approach for overcoming the T-cell deficiency in Hodgkin's disease and might be exploited clinically. As upregulation of the zeta chain can also be achieved using bispecific monoclonal antibodies (BI-MoAbs) with specificity for tumor antigens and CD3 and CD28, respectively, an immunotherapy with CD3/CD30 and CD28/CD30 Bi-MoAbs may overcome and should therefore, not be jeopardized by the inherent T-cell deficiency in patients with Hodgkin's disease.

Adolescent↗
PubMed1996

Cure of disseminated xenografted human Hodgkin's tumors by bispecific monoclonal antibodies and human T cells: the role of human T-cell subsets in a preclinical model.

Cure of a single established human Hodgkin's tumor growing subcutaneously in severe combined immunodeficient (SCID) mice can be achieved with a complex protocol using two bispecific monoclonal antibodies (Bi-MoAb) directed against the Hodgkin's associated CD30 antigen and the T-cell triggering molecules CD3 and CD28, respectively, together with human T cells prestimulated in vitro with Bi-MoAbs in the presence of CD30+ cells. To adapt this model to the clinical situation, disseminated tumors were established in SCID mice by intravenous injection of 2 x 10(7) cells of the Hodgkin's derived cell line L540CY. Treatment of SCID mice bearing disseminated CD30+ Hodgkin's tumors with the combination of CD3/CD30 and CD28/CD30 Bi-MoAbs and naive (ie, not in vitro prestimulated) human T cells resulted in the cure of all appropriately treated animals. T lymphocytes obtained from patients with advanced stage untreated Hodgkin's disease were as effective as lymphocytes from healthy controls. Treatment was effective even when delayed until 2 weeks after tumor inoculation, and application of Bi-MoAbs into SCID mice with circulating human T cells was as effective as injecting the Bi-MoAbs before the lymphocytes. Treatment results with isolated CD4+ and CD8+ human T cells suggest that both subsets are necessary for the Bi-MoAb mediated cure of xenografted human tumors in vivo. The efficacy and practicability of this preclinical immunotherapy protocol support and form the basis for the clinical evaluation of this approach in patients with Hodgkin's disease resistant to standard therapy.

Animals↗
PubMed1996

Expansion of cytokine-producing CD4-CD8- T cells associated with abnormal Fas expression and hypereosinophilia.

The mechanisms of sustained overproduction of eosinophils in the idiopathic hypereosinophilic syndrome and in some human immunodeficiency virus (HIV)-1-infected individuals are largely unknown. We hypothesized that T cells may release soluble products that regulate eosinophilia in these patients, as has been previously shown in bronchial asthma. We identified one patient with idiopathic hypereosinophilic syndrome and one HIV-1-infected individual with associated hypereosinophilia who demonstrated high numbers of CD4-CD8- T cells in peripheral blood. CD4-CD8- T cells from both patients, although highly activated, did not express functional Fas receptors. In one case, the lack of functional Fas receptors was associated with failure of Fas mRNA and protein expression, and in another, expression of a soluble form of the Fas molecule that may have antagonized normal signaling of Fas ligand. In contrast to the recently described lymphoproliferative/autoimmune syndrome, which is characterized by accumulation of CD4-CD8- T cells and mutations within the Fas gene, this study suggests somatic variations in Fas expression and function quite late in life. Both genetic and somatic abnormalities in regulation of the Fas gene are therefore associated with failures to undergo T cell apoptosis. Furthermore, the expanded population of CD4-CD8- T cells from both patients elaborated cytokines with antiapoptotic properties for eosinophils, indicating a major role of these T cells in the development of eosinophilia. Thus, this study demonstrates a sequential dysregulation of apoptosis in different cell types.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Gracilis muscle transposition in the treatment of faecal incontinence.

Between 1965 and 1994 eight selected patients with faecal incontinence for solid stool (Grade 4) were operated on by the original procedure described by Pickrell (1952), combined with biofeedback training postoperatively. No postoperative complication occurred. All patients were improved by this procedure. Five had normal continence and there were 3 incontinence for flatus. Anal manometry showed an increase in postoperative squeeze pressure (p < 0.05). Long term results (48.5 months) remained the same in five cases. One patient became incontinent following an anal dilatation at 108 months, and two required excision of mucosal ectropion at 7 and 78 months with restoration of continence. One patient died of unrelated disease at 31 months.

Adult↗
PubMed1996

HLA-A2-restricted peripheral blood cytolytic T lymphocyte response to HPV type 16 proteins E6 and E7 from patients with neoplastic cervical lesions.

The DNA from human papillomavirus (HPV) can be detected in 90% of cervical carcinomas. To address whether patients infected with HPV can mount efficient T cell responses to this pathogen we examined the cytotoxic T lymphocyte (CTL) response of peripheral blood mononuclear cells (PBMC) from patients with abnormal genital epithelial cells. PBMC from 11 HLA-A2+ patients were stimulated with CaSki, a cervical carcinoma cell line that is HPV 16+ and HLA-A2+. The CTL were screened for reactivity to the cervical carcinoma cell line C33A (HPV-, HLA-A2+) transfected with the HPV 16 E6 or E7 genes or the plasmid without insert. The CTL of 1 patient showed particularly strong CaSki and HPV E6 or E7 protein-specific cytotoxicity in a HLA-A2+-restricted fashion. In contrast, these CTL lysed neither a vector-only transfectant, the natural killer cell (NK) target, K562 nor the lymphokine-activated killer cell (LAK) target, Daudi. HLA-A2 restriction was demonstrated by the lack of recognition of a HLA-A2- CaSki cell line developed in our laboratory. The CTL line was cloned and 99 clones were harvested and screened; 51 clones lysed CaSki, of which 17 did not lyse the A2- CaSki. Of these HLA-A2- restricted clones, 8 did not lyse C33A transfectants, 6 lysed all C33A transfectants, 3 lysed C33A-E7 only and none lysed C33A-E6 only. These data imply that, within the bulk CTL line, HLA-A2-restricted recognition of antigens was restricted to CaSki antigens, antigens common to cervical carcinoma (CaSki plus C33A), or HPV-16-E7-derived antigen on the clonal level. The E7-restricted clones were negative for recognition of known HLA-A2-binding peptides from E7.

Base Sequence↗
PubMed1996

Lack of DNA synthesis among CD34+ cells in cord blood and in cytokine-mobilized blood.

Flow cytometric DNA analysis was performed in combination with three-colour immunological staining of cell surface antigens on density-separated mononuclear cells (MNC) obtained from peripheral blood (PB) before, during and after cytokine stimulation of healthy adults. The aim of the study was to determine the cell-cycling status of haemopoietic progenitor cells mobilized into the blood of healthy volunteers during a 5 d treatment period with 5/micrograms per kg body weight of either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-simulating factor (GM-CSF). Despite considerably increasing numbers of CD34+ PB MNC, the latter were not found to be in S/G2M phase, whereas, among the CD34- MNC, the proportion of cells in S/G2M phase increased from < 0.1% to 0.75 +/- 0.4% (GM-CSF) and to 1.34 +/- 0.75% (G-CSF) and dropped again after discontinuation of the cytokine stimulation. These cells expressed CD33 but were negative for CD45RA, CD3, CD19 and CD14 and were thus considered granulopoietic cells. Analogous results were obtained from analyses of cord blood (CB). In contrast, CD34+ cells from bone marrow (BM) were partially (between 9% and 15%) found to be in S/G2M phase. The non-cycling status of PB and progenitor cells was confirmed by the analysis of CD34+ cells enriched from the two cells sources. However, in vitro stimulation of these progenitor cells using IL3, GM-CSF, erythropoietin and steel factor (SF) revealed that, after 48 h in suspension culture, up to 30% of the CD34+ cells were in S/G2m phase. The fact that cycling CD34+ cells are only detectable in BM but not in PB or CB may suggest different adhesive properties of migrating/mobilized 'stem cells' which may require the BM micro-environment for adequate proliferation in vivo.

Adult↗
PubMed1996

Characterization of the human jumonji gene.

While constructing a cDNA library of human embryos, we have isolated a clone homologous to jumonji, a mouse gene required for neural tube formation. We have determined the complete coding sequence of the human homologue (JMJ) and deduced the amino acid sequence of the putative protein. We show here that human and mouse jumonji putative proteins are homologous and present 90% identity. During human embryogenesis, JMJ mRNAs are predominantly expressed in neurons and particularly in dorsal root ganglion cells. They are also expressed in neurons of human adult cerebral cortex. In view of these observations, we propose JMJ as a candidate gene for developmental defects of the central nervous system in the human. The human JMJ gene maps at position 6p24-6p23.

Amino Acid Sequence↗
PubMed1996

Long-term outcome of idiopathic hypereosinophilic syndrome--transition to eosinophilic gastroenteritis and clonal expansion of T-cells.

We describe a patient with idiopathic hypereosinophilic syndrome, without initial gastrointestinal symptoms, and their transition to eosinophilic gastroenteritis. This patient, a 65-year-old man, presented with fever, constitutional symptoms, peripheral and bone marrow eosinophilia 20 years ago. During the course of the disease, diarrhoea and malabsorption became prominent, whereas bone marrow eosinophilia regressed completely and blood eosinophilia regressed partially. Biopsies showed a severe eosinophilic gastroenteritis of the mucosal type involving the stomach, small bowel and colon. During the final years of the patient's disease, mucosal eosinophilia became less intense and a mucosal infiltration with T-cells dominated. At autopsy, immunopathological studies of small intestines and colon specimens showed a clonal expansion of morphologically normal T-cells in the intestinal mucosa, which expressed the abnormal phenotype CD2+CD3+CD4-CD5-CD8-. Flow cytometry examination of peripheral blood revealed a corresponding abnormal population of CD3+CD4-CD8- T-cells, indicating a systemic spread of the process. The patient eventually died of non-obstructive small bowel infarction with peritonitis 20 years after the onset of the first symptoms. We postulate that the destructive eosinophilic/lymphocytic inflammation is caused by a clonal proliferation of T-lymphocytes with probable secretion of Type 2 T(helper) cell cytokines and consecutive stimulation of eosinophils.

Aged↗