Biomedical subjects

Christian Kneitz

Publications and source records attributed to Christian Kneitz.

11 recordsLinked to original sources

PubMed2006

Sustained JNK activation in response to tumor necrosis factor is mediated by caspases in a cell type-specific manner.

In most cell types, tumor necrosis factor (TNF) induces a transient activation of the JNK pathway. However, in NFkappaB-inhibited cells, TNF stimulates also a second sustained phase of JNK activation, which has been implicated in cell death induction. In the present study, we have analyzed the relationship of cell death induction, caspase activity, JNK, and NFkappaB stimulation in the context of TNF signaling in four different cellular systems. In all cases, NFkappaB inhibition enhanced TNF-induced cell death and primed most, but not all, cells for sustained JNK activation. The caspase inhibitor Benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethyl ketone (Z-VAD-fmk) and overexpression of the antiapoptotic proteins FLIP-L and Bcl2 differentially blocked transient and sustained JNK activation in NFkappaB-inhibited KB and HaCaT cells, indicating that the two phases of TNF-induced JNK activation occur at least in these cellular models by different pathways. Although the broad range caspase inhibitor Z-VAD-fmk and the antioxidant butylated hydroxyanisole interfered with TNF-induced cell death to a varying extent in a cell type-specific manner, inhibition of JNK signaling had no or only a very moderate effect. Notably, the JNK inhibitory effect of neither Z-VAD-fmk nor butylated hydroxyanisole was strictly correlated with the capability of these compounds to rescue cells from TNF-induced cell death. Thus, sustained JNK activation by TNF has no obligate role in TNF-induced cell death and is mediated by caspases and reactive oxygen species in a cell type-specific manner.

Animals↗

PubMed2006

Assessment of a case-based training system (d3web.Train) in rheumatology.

To improve the learning experiences for third year medical students, a case-based training program based on real patient records has been introduced as a supplement to lectures. It was built with the novel training environment d3web.Train. Optimization of the learning environment d3web.Train for both teachers and learners has been considered as equally important and offers several trade-offs. The training program has been evaluated during three subsequent rheumatology courses, the first one voluntary and the latter two mandatory. For each course, we tracked how often and intensive each student used the system. In addition, the students answered questionnaires about their expectations and experiences. In the first voluntary course, 39/92 students finished at least one case and solved 187 cases in total (average: 4.8 cases from 12 cases available). In the second and third mandatory courses, all students (60 resp. 56) finished at least the required 20 cases with an average usage of 22.5 resp. 29.3 out of 31 available cases. Most of the cases were processed twice by the students in preparation for the final examinations. A positive correlation between processed cases per student and the exam score could be shown (30, 73 and 95% in the first, second and third courses, respectively). The findings clearly exceeded the expectations of the students concerning its usefulness as a supplement to lectures and as good preparation for their job as physician, as well as the learning period to use the program. For working through one case, students needed about 9 min on average. The case-based training system d3web.Train offers a new tool for medical education in rheumatology. The main advantage of the system is the relatively low effort needed to create a case-based program starting from the available dismissal records.

Computer-Assisted Instruction↗

PubMed2006

Regeneration of B cell subsets after transient B cell depletion using anti-CD20 antibodies in rheumatoid arthritis.

OBJECTIVE: Transient B cell depletion with the monoclonal anti-CD20 antibody rituximab has resulted in favorable clinical responses in patients with rheumatoid arthritis (RA). However, little is known about the regeneration profile of different peripheral B cell subpopulations. The aim of this study was to delineate the regeneration profile of different B cell subsets in the peripheral blood after selective anti-CD20-mediated B cell depletion. METHODS: Seventeen patients with RA refractory to standard therapy were treated with rituximab. Patients 1-6 received 4 weekly infusions of rituximab at a dose of 375 mg/m2, and patients 7-17 received 2 infusions of rituximab (1,000 mg), 2 weeks apart. Four-color staining was performed at several time points, using CD38, IgD, and CD27 in addition to other cell surface markers. In one patient, the mutational status of the immunoglobulin receptor was examined. RESULTS: The analysis revealed a distinct pattern of B cell regeneration. The first wave of repopulating B cells were immature B cells (CD38high,IgD+,CD10+,CD24high), the immunoglobulin receptors of which were not yet somatically mutated. In parallel, a recirculation of plasma cells was observed. Later, the number of naive B cells increased, and these cells predominated in the peripheral blood B cell pool. CD27+ memory B cells showed a slow and delayed repopulation, and the level of these cells stayed significantly reduced (<50%) compared with baseline values, for more than 2 years. CONCLUSION: Our findings provide evidence for a characteristic regeneration pattern of B cell subpopulations, with long-lasting modulation of B cell subset composition, after selective anti-CD20-mediated B cell depletion.

Adult↗

PubMed2005

Evaluation of a novel case-based training program (d3web.Train) in hematology.

The new media such as the internet and digital imaging offer new opportunities in medical education. In addition to conventional lectures, we developed a case-based simulation training program of 17 hematology cases using the novel training system d3web.Train. We evaluated the assessment of this internet course by medical students, as well as their results in the hematology exam. From a group of 150 students, 47 worked through at least one case and solved 435 cases in total; in average, these students solved 9.5 cases. Eighteen different students filled in a questionnaire about the training system and 68 questionnaires about individual cases. The main results were the students found the cases very helpful (1.5+/-0.6 on a scale from 1=very helpful to 5=not at all), the training system very good (1.4+/-0.5 on a scale from 1 to 6), and want to work with it further (1.2+/-0.4 on a scale from 1 to 5). During the final examination, those 16 students who answered that they had solved more than 5 from the 17 cases scored significantly better (two-sided t test, p<0.01) in the hematological part of the exam than those 34 students solving 0 to 5 cases. To our knowledge, this is the first student evaluation of a case-based training program in general hematology. The d3web.Train system offers a new and great tool for creating a training program in a reasonable amount of time, because it is able to process available patient records.

Computer-Assisted Instruction↗

PubMed2005

Regeneration of the immunoglobulin heavy-chain repertoire after transient B-cell depletion with an anti-CD20 antibody.

B-cell depletive therapies have beneficial effects in patients suffering from rheumatoid arthritis. Nevertheless, the role of B cells in the pathogenesis of the disease is not clear. In particular, it is not known how the regeneration of the B-cell repertoire takes place. Two patients with active rheumatoid arthritis were treated with rituximab, and the rearranged immunoglobulin heavy-chain genes (Ig-VH) were analysed to follow the B-cell regeneration. Patient A was treated with two courses of rituximab, and B-cell regeneration was followed over 27 months by analysing more than 680 Ig-VH sequences. Peripheral B-cell depletion lasted 7 months and 10 months, respectively, and each time was accompanied by a clinical improvement. Patient B received one treatment course. B-cell depletion lasted 5 months and was accompanied by a good clinical response. B cells regenerated well in both patients, and the repopulated B-cell repertoire was characterised by a polyclonal and diverse use of Ig-VH genes, as expected in adult individuals. During the early phase of B-cell regeneration we observed the expansion and recirculation of a highly mutated B-cell population. These cells expressed very different Ig-VH genes. They were class-switched and could be detected for a short period only. Patient A was followed long term, whereby some characteristic changes in the VH2 family as well as in specific mini-genes like VH3-23, VH 4-34 or VH 1-69 were observed. In addition, rituximab therapy resulted in the loss of clonal B cells for the whole period. Our data show that therapeutic transient B-cell depletion by anti-CD20 antibodies results in the regeneration of a diverse and polyclonal heavy-chain repertoire. During the early phase of B-cell regeneration, highly mutated B cells recirculate for a short time period in both the patients analysed. The longitudinal observation of a single patient up to 27 months shows subtle intraindividual changes, which may indicate repertoire modulation.

Antibodies, Anti-Idiotypic↗

PubMed2003

Semiquantitative and qualitative assessment of B-lymphocyte V H repertoire by a fluorescent multiplex PCR.

We established a new tool to perform semiquantitative and qualitative screening for V(H) gene usage frequency during IgH rearrangements in human B-lymphocytes. In two separate multiplex PCRs, the rearranged VDJ regions were amplified with V(H) family-specific primers labeled with different fluorescent dyes (FAM, HEX, NED, or ROX). The relative amount of each of the particular V(H) family products and their ratios were determined by fragment analysis on a ABI PRISM 377 sequencer. We verified that the fluorescent multiplex PCR (FMPCR) shows high specificity and sensitivity, acceptable reproducibility and reliability. Data obtained were well in agreement with results revealed by sequencing following single-cell PCR. Ten healthy volunteers showed a comparable semiquantitative V(H) family distribution. The FMPCR also correctly detected a monoclonal peak in a CLL patient. Thus, labeling primers with various fluorescent dyes allows for an assessment of V(H) family usage and an immediate determination of the involved V(H) gene family if any clonal peaks are present. This method provides a quick, easy, and reliable tool for V(H) repertoire screening of larger populations of patients suffering from diseases with changes in the V(H) repertoire allowing for selection of cases worth a more detailed and cumbersome sequence analysis later on.

Adult↗

PubMed2003

Pax-5 is a key regulator of the B cell-restricted expression of the CD23a isoform.

Human CD23 (the low affinity IgE receptor) is a B cell differentiation marker involved in inflammatory responses. Two isoforms (CD23a and CD23b) are known, which differ only in their cytoplasmic domain. Whereas CD23b expression is specifically induced by IL-4 on B cells and cells of the myeloid lineage, CD23a expression is restricted to B cells. Each isoform is regulated by its own promoter. Pax-5 is a B-cell-restricted transcription factor with an essential role in early and late B cell development. Analyses of the CD23a promoter revealed a Pax-5-binding site, which can compete a high affinity Pax-5-binding site or directly bind Pax-5 protein in electrophoretic mobility shift assays. Introducing mutations into this site abrogates the binding. Expression of Pax-5 in 293 cells resulted in a seven- to tenfold activation of a CD23a core promoter construct. Most importantly, ectopic expression of Pax-5 in the monocytic cell line U-937, which regularly expresses only the CD23b isoform, led to CD23a expression after stimulation with IL-4 and PMA. Our results suggest that Pax-5 is a key regulator of the B-cell-restricted expression of the CD23a isoform.

B-Lymphocytes↗

PubMed2003

Nucleoporin p62 antibodies in a case of mixed connective tissue disease.

Mixed connective tissue disease is an overlap syndrome characterized by features of different systemic autoimmune diseases and a high titer of U1-snRNP antibodies. We examine here the autoantibodies to nucleoporin p62 in a severe case of mixed connective tissue disease in a young male patient. Thus far, p62 antibodies have mainly been described in cases of primary biliary cirrhosis. We speculate that the presence of p62 antibodies is an indication of a poor prognosis in connective tissue disorders.

Adult↗

PubMed2002

The CD23b promoter is a target for NF-AT transcription factors in B-CLL cells.

CD23 is atypically highly expressed in various chronic diseases, including B-CLL, lupus erythematodes and rheumatoid arthritis. Its expression can be further enhanced by interleukin 4 (IL-4). We have shown before that in B-CLL cells nuclear factor(s) of activated T cells (NF-ATs) show permanent nuclear localization and therefore constitutive transcriptional activity. Here we identify CD23b promoter as a novel target for NF-AT factors in B-CLL cells. The CD23b promoter contains two NF-AT binding sites to which NF-ATp and NF-ATc factors bind with high affinity. Mutations introduced into these sites abolished NF-AT binding and impaired the promoter activity, as did cyclosporin A (CsA), an inhibitor of nuclear transport of NF-ATs. Furthermore, we show that IL-4-induced transcription factor STAT6 cooperates with NF-ATs in the induction of the CD23b promoter activity. These results show that the CD23b promoter is a target for NF-AT factors and suggest that the cooperation between NF-AT and STAT factors might be one of the molecular mechanisms responsible for high-level expression of CD23 on the surface of B-CLL cells.

Base Sequence↗

PubMed2002

Regulation of CD23 isoforms on B-chronic lymphocytic leukemia.

CD23 is constitutively and atypically expressed on malignant B-cells in patients with chronic lymphocytic leukemia. It exists in two isoforms that differ only in a short amino acid sequence at the N-terminus. The CD23a isoform exhibits an endocytosis signal, that renders it more efficient in antigen uptake than CD23b. Therefore, we analyzed the regulation of CD23 isoforms and tested the ability to stimulate T-cell clones by targeting antigen to CD23 on CLL B-cells. Investigation of several stimulators to promote CD23a expression on CLL versus normal B-cells confirmed a different CD23 regulation in B-CLL. We did not find any evidence for a differential regulation of the two CD23 isoforms in B-CLL. However, CD23a is always predominantly expressed with a constant ratio of CD23a:CD23b. We show that antigen targeted to CD23 on CLL B-cells is very efficiently presented. Therefore, CD23 is likely to provide a suitable target for receptor-mediated antigen presentation in B-CLL which can be used to activate a T-cell response.

Antigen Presentation↗

PubMed2002

Effective B cell depletion with rituximab in the treatment of autoimmune diseases.

In a pilot study four patients with systemic lupus erythematosus (SLE) and autoimmune thrombocytopenia (ITP) were treated with rituximab, a B cell depicting chimeric human/mouse anti-CD20 antibody. Treatment could be performed without serious side effects and resulted in a depletion of B cells from the peripheral blood for at least 4 months. Examination of one patient three months after treatment revealed a complete depletion of B cells in the bone marrow and in the spleen as well. The time point when peripheral B cells returned into the normal range varied between 8 months and over one year and could be observed also in the spleen. The follow up over more than 12 months revealed no significant treatment-associated side effects. Total immunoglobulin and specific antibody levels did not change except for one SLE-patient receiving additional immunosuppressive treatment including cyclophosphamide because of progressive disease. Clinical effectiveness cannot be judged by the small number of patients. However, one SLE patient with refractory severe thrombocytopenia had a very Favourable response with stable platelet numbers over 100.000/microl now for more than 6 months and disappearance of anti-DNA antibodies. The treatment failure in another SLE patient could be due to the persistence of CD20-negative plasmablasts in peripheral blood which are not targeted by anti-CD20 treatment. Further studies are needed to assess the clinical benefit of B cell depletion in the treatment of autoimmune diseases.

Adult↗