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Biomedical subjects

R Buhmann

Publications and source records attributed to R Buhmann.

8 recordsLinked to original sources
PubMed2004

Quantitative analysis of pulmonary perfusion using time-resolved parallel 3D MRI - initial results.

PURPOSE: To assess the use of time-resolved parallel 3D MRI for a quantitative analysis of pulmonary perfusion in patients with cardiopulmonary disease. MATERIALS AND METHODS: Eight patients with pulmonary embolism or pulmonary hypertension were examined with a time-resolved 3D gradient echo pulse sequence with parallel imaging techniques (FLASH 3D, TE/TR: 0.8/1.9 ms; flip angle: 40 degrees; GRAPPA). A quantitative perfusion analysis based on indicator dilution theory was performed using a dedicated software. RESULTS: Patients with pulmonary embolism or chronic thromboembolic pulmonary hypertension revealed characteristic wedge-shaped perfusion defects at perfusion MRI. They were characterized by a decreased pulmonary blood flow (PBF) and pulmonary blood volume (PBV) and increased mean transit time (MTT). Patients with primary pulmonary hypertension or Eisenmenger syndrome showed a more homogeneous perfusion pattern. The mean MTT of all patients was 3.3 - 4.7 s. The mean PBF and PBV showed a broader interindividual variation (PBF: 104 - 322 ml/100 ml/min; PBV: 8 - 21 ml/100 ml). CONCLUSION: Time-resolved parallel 3D MRI allows at least a semi-quantitative assessment of lung perfusion. Future studies will have to assess the clinical value of this quantitative information for the diagnosis and management of cardiopulmonary disease.

Acute Disease↗
PubMed2001

New aspects on the pathogenesis, diagnostic procedures, and therapeutic management of chronic lymphocytic leukemia.

Chronic lymphocytic leukemia of the B-cell type (B-CLL) is the most frequently occurring leukemia in the Western hemisphere. Until 10 years ago, the basic medical approach to this disease was expectative and palliative. Chemotherapy with alkylating agents such as chlorambucil used to be the main therapeutic option, and only patients at advanced stages of B-CLL were treated. With the advent of new treatments such as purine analogs, high-dose therapy followed by hematopoietic progenitor support, monoclonal antibodies, and further immunotherapies, this paradigm is about to change. By using these combinations, younger patients with active disease are now treated with the goal of a long-lasting remission. More sophisticated techniques allow characterization of some of the underlying molecular genetic aberrations and (together with new serum parameters) more accurate prediction of individual prognoses than with the clinical staging systems. With the help of these developments, patients with B-CLL will be managed according to their individual risk with a watch-and-wait strategy in patients with the most indolent form of the disease, conventional chemotherapy with alkylating agents and/or purine analogs in patients at intermediate risk, and aggressive high-dose chemotherapy (followed by immunotherapy) in patients with the most aggressive form of the disease.

Antineoplastic Agents↗
PubMed2000

Reconstitution of the cellular immune response after autologous peripheral blood stem cell transplantation in patients with non-Hodgkin's lymphoma.

Peripheral blood stem cell (PBSC) transplants may be depleted of lymphoid progenitors, thereby disabling the cellular immune response against viral pathogens after autologous PBSC transplantation (PBSCT). To monitor the cellular immune reconstitution after autologous PBSCT, we investigated the cytolytic activity (CLA) of peripheral blood T lymphocytes against Epstein-Barr virus (EBV) in 13 patients with non-Hodgkin's lymphoma or multiple myeloma. The individual EBV-directed CLA (EBV-CLA) was determined by calculating the number of cytolytic effector cells in 106 T cells needed to lyse 25% of autologous EBV-transformed B-lymphoblastoid cells, expressed as lytic units (LU25). During the first 6 months after PBSCT, the EBV-CLA was only 14.6% of the response of healthy controls (median 4. 8 vs. 32.9 LU25). Thereafter, the EBV-CLA increased to 28.15 LU25 (median) or 86% of healthy controls. Monthly follow-up analyses in five selected patients showed that the EBV-CLA was barely detectable at 4 weeks and recovered at 8-12 weeks after PBSCT in four out of five patients. Effector cells consisted mostly of CD8-positive T lymphocytes, with small CD4- and CD3/CD56-positive lymphocyte fractions. These results suggest that the reconstitution of the cellular immune response against EBV takes 8-12 weeks after autologous PBSCT.

Female↗
PubMed1999

CD40-activated B-cell chronic lymphocytic leukemia cells for tumor immunotherapy: stimulation of allogeneic versus autologous T cells generates different types of effector cells.

Although spontaneous remissions may rarely occur in B-cell chronic lymphocytic leukemia (B-CLL), T cells do generally not develop a clinically significant response against B-CLL cells. Because this T-cell anergy against B-CLL cells may be caused by the inability of B-CLL cells to present tumor-antigens efficiently, we examined the possibility of upregulating critical costimulatory (B7-1 and B7-2) and adhesion molecules (ICAM-1 and LFA-3) on B-CLL cells to improve antigen presentation. The stimulation of B-CLL cells via CD40 by culture on CD40L expressing feeder cells induced a strong upregulation of costimulatory and adhesion molecules and turned the B-CLL cells into efficient antigen-presenting cells (APCs). CD40-activated B-CLL (CD40-CLL) cells stimulated the proliferation of both CD4(+) and CD8(+) T cells. Interestingly, stimulation of allogeneic versus autologous T cells resulted in the expansion of different effector populations. Allogeneic CD40-CLL cells allowed for the expansion of specific CD8(+) cytolytic T cells (CTL). In marked contrast, autologous CD40-CLL cells did not induce a relevant CTL response, but rather stimulated a CD4(+), Th1-like T-cell population that expressed high levels of CD40L and released interferon-gamma in response to stimulation by CD40-CLL cells. Together, these results support the view that CD40 activation of B-CLL cells might reverse T-cell anergy against the neoplastic cell clone, although the character of the immune response depends on the major histocompatibility complex (MHC) background on which the CLL or tumor antigens are presented. These findings may have important implications for the design of cellular immunotherapies for B-CLL.

Aged↗
PubMed1999

Therapeutic plasma exchange in patients suffering from thrombotic microangiopathy after allogeneic bone marrow transplantation.

Thrombotic microangiopathy (TM) is a potentially fatal complication of allogeneic bone marrow transplantation (BMT). The underlying pathophysiology is thought to be generalized endothelial cell damage caused by several factors including conditioning treatment, cyclosporin A (CsA), or graft versus host disease (GVHD). In the present retrospective study, 6 patients suffering from Grade 2 BMT-TM at a mean of 62 days post BMT were treated by 3-15 daily sessions of therapeutic plasma exchange (TPE). In most sessions, cryosupernatant (CSN) of plasma, in some fresh frozen plasma (FFP) was used as the substitution fluid. All patients suffered from acute graft versus host disease (aGVHD) of the skin, which was treated by CsA. CsA was withdrawn in all patients. TPE caused a response in 4 of 6 patients evidenced by a decrease to Grade 0 (n = 3) or 1 (n = 1) BMT-TM. Only 1 patient had mild renal insufficiency which did not improve during TPE. While all patients were dependent on platelet transfusions at baseline, the platelet counts improved in 2 of 6 patients after the TPE course. One patient did not show any response to TPE with FFP, and his disease improved only after CSN was introduced as substitution fluid (Grade 0). Four patients were still alive 175-495 days post BMT, and 2 patients died about 2-3 weeks after the end of the TPE course, 1 from cachexia and 1 from systemic aspergillosis. In summary, in this pilot study, TPE positively influenced BMT-TM, especially if CSN was used as the substitution fluid.

Adult↗
PubMed1998

Assessment and characterization of the cytolytic T lymphocyte response against Epstein-Barr virus in patients with non-Hodgkin's lymphoma after autologous peripheral blood stem cell transplantation.

The cytolytic T lymphocyte (CTL) response has often been used to assess the reconstitution of T cell function after allogeneic or autologous bone marrow transplantation (BMT). Less is known, however, about the reconstitution of the CTL response after peripheral blood stem cell transplantation (PBSCT). Therefore, we investigated the CTL response against Epstein-Barr virus (EBV) of patients undergoing autologous PBSCT. CTLs of six patients with relapsed non-Hodgkin's lymphoma and multiple myeloma were established before and at different times after PBSCT by in vitro stimulation of peripheral blood lymphocytes with autologous EBV-transformed lymphoblastoid cell lines (LCLs). The efficiency of T cell priming by LCLs was assessed at the time of initiation of CTL lines; the proliferative response was strongly reduced during the first 4 months and increased 5 months or more following PBSCT. Cytolytic activity was measured after three or four restimulations of CTLs. All patients investigated had a detectable EBV-specific CTL response which was poor during the first weeks after transplantation, accompanied by a strong non-MHC-restricted cytotoxic activity and a high proportion of CD56-positive T cells. Five or more months after PBSCT, a specific CTL response against EBV was seen which was similar to the situation prior to PBSCT, while the unspecific cytotoxic response decreased. Blocking experiments with monoclonal anti-CD3, anti-CD8 or anti-MHC I antibodies resulted in substantial inhibition of autologous LCL lysis, whereas anti-CD4 or anti-MHC II antibodies had no effect. Finally, autologous PHA blasts of a patient with the HLA haplotype A1/9+, B5/8+, Cw4/7+, were loaded with various EBNA-derived nonapeptides known to be presented by HLA B8 or A11, and exposed to autologous, EBV-directed CTLs. Specific lysis by CTLs only occurred with HLA B8-, but not with HLA A11-restricted nonapeptides. This demonstrated the existence of an MHC I-restricted anti-EBV CTL response after PBSCT. Taken together, the results show that the anlaysis of the EBV-directed CTL activity may serve as a surrogate marker to assess the reconstitution of the cellular immune response in patients undergoing autologous PBSCT.

Amino Acid Sequence↗
PubMed1997

Gene transfer of the costimulatory molecules B7-1 and B7-2 into human multiple myeloma cells by recombinant adeno-associated virus enhances the cytolytic T cell response.

Gene transfer of the costimulatory molecules B7-1 and B7-2 induces a potent antitumor immune response in a variety of tumor models. B cell neoplasms including multiple myeloma (MM) often show little or no expression of B7 antigens; they are therefore a potential target for this approach. To increase the expression of human B7 genes in MM cells, both genes and the neomycin phosphotransferase gene were packaged into recombinant adeno-associated virus vectors (rAAV). The resulting recombinant viruses rAAV/B7-1, rAAV/B7-2 and rAAV/Neo were used to transduce the MM cell lines LP-1 and RPMI 8226. This allowed the transduction of up to 80% of LP-1 cells 4 days after infection with purified rAAV particles. The response of human allogeneic T cells to rAAV/B7-1 and rAAV/B7-2 transduced, gamma-irradiated LP-1 cells was assessed by [3H]thymidine incorporation, by RT-PCR-based detection of immunostimulatory cytokine transcripts and by ELISA quantification of cytokines in the supernatant. Stimulation of T cells with rAAV/B7-1 or rAAV/B7-2 transduced LP-1 cells resulted in an up to 10-fold increase of T cell proliferation when compared with LP-1 cells transduced with rAAV/Neo. Similar results were obtained with RPMI 8226 cells. Both rAAV/B7-1 and rAAV/B7-2 transduced LP-1 cells stimulated the T cell secretion of IL-2 and IFN-gamma. Furthermore, [51Cr] release assays showed that rAAV/B7-1 or rAAV/B7-2 transduced LP-1 cells induced a cytolytic T cell (CTL) response, in contrast to LP-1 cells transduced with rAAV/Neo. In all assays, the effects of rAAV/B7-1 and rAAV/B7-2 were similar. Taken together, the results show that rAAV-mediated transfer of B7 genes into MM cell lines is able to enhance the antitumor T cell response and to elicit a cytolytic T cell response.

Antigens, CD↗