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Biomedical subjects

W Weimar

Publications and source records attributed to W Weimar.

At least 19 recordsLinked to original sources
PubMed1992

Effects of cyclosporin A on glomerular barrier function in the nephrotic syndrome.

1. To elucidate the mechanisms by which cyclosporin A diminishes proteinuria, we studied 20 patients with severe nephrotic syndrome. Biopsy-established pathologies included minimal change disease (n = 5), membranous glomerulopathy (n = 6), membranoproliferative glomerulonephritis (n = 5) and focal segmental glomerulosclerosis (n = 4). Before, at the end of a 90 day course of cyclosporin A, and finally 1 month after stopping cyclosporin A we determined 24 h protein excretion. Measurements of glomerular filtration rate, effective renal plasma flow, fractional clearance rates of albumin and immunoglobulins with different charges and the transglomerular sieving of uncharged dextrans of broad size distribution were used to study the effects of cyclosporin A on renal perfusion and the glomerular filtration barrier. The findings were analysed with a theoretical model of solute transport. 2. Among the different forms of glomerulopathy the response to low-dose cyclosporin A (trough levels 32.0-36.9 ng/ml) varied markedly. In minimal change disease, proteinuria decreased from 9.5 +/- 3.1 to 1.3 +/- 0.2 g/24 h (mean +/- SEM, P less than 0.01). This response was due to restoration of the charge selectivity of the glomerular barrier. The depressed value of the glomerular permeability coefficient also returned to normal. Glomerular filtration rate, effective renal plasma flow and renal vascular resistance did not change. Proteinuria returned after stopping cyclosporin A, although it did not reach pretreatment levels. In membranous glomerulopathy, proteinuria fell from 9.9 +/- 1.5 to 1.8 +/- 0.3 g/24 h (P less than 0.01). Changes in protein excretion and dextran sieving were compatible with an increase in glomerular permselectivity and a decrease in filtrate flow through the 'shunt' pathway. Glomerular filtration rate was maintained, although effective renal plasma flow fell significantly. Proteinuria relapsed after stopping cyclosporin A. In membranoproliferative glomerulonephritis and focal segmental glomerulosclerosis proteinuria did not respond to cyclosporin A, although cyclosporin A exerted important haemodynamic effects. 3. In minimal change disease and membranous glomerulopathy cyclosporin A exerts its beneficial effects on proteinuria through changes in the properties of the glomerular barrier, resulting in increased charge and size selectivity, respectively.

Adult↗
PubMed1992

Too early for cardiac transplantation--the right decision?

In 109 out of 479 patients who were referred for cardiac transplantation it was considered to be too early to put them on the waiting list for a donor heart. The clinical course of these 109 patients was analysed in order to verify whether this decision had been right. The mean age of the patients was 43 years, half of them suffered from ischaemic heart disease. The systolic left ventricular function of the patients was severely depressed (mean left ventricular ejection fraction 21%) and the left ventricular cavity was markedly dilated (mean echocardiographic end diastolic dimension 73 mm). Functional capacity, measured by bicycle ergometry, was low: mean maximal workload 62% of the expected load for gender, height and age. The median follow-up duration was 31 months. The survival rate of the patients was better than that of 175 patients who were accepted for transplantation after referral, 92%, 87%, 81%, 71% and 73%, 73%, 71%, 68% after 1, 2, 3 and 4 years respectively. Re-assessment was necessary in 29% of the patients within 1 year and in 52% within 3 years. Twenty patients died: 12 patients died before re-assessment had been initiated (eight sudden deaths), six patients because of progressive heart failure before heart transplantation could be performed and two patients died after heart transplantation. Left ventricular ejection fraction, pulmonary capillary wedge pressure and transpulmonary gradient were not reliable predictors of the course of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Acute rejection in heart transplant patients is associated with the presence of committed donor-specific cytotoxic lymphocytes in the graft but not in the blood.

In vivo-activated, committed donor-specific cytotoxic lymphocytes (cCTL) can be propagated and expanded from endomyocardial biopsies (EMB) in IL-2-enriched medium especially during an acute rejection episode. We report here our efforts to detect these cCTL by the same technique in peripheral blood at the moment of rejection and when no rejection was diagnosed. During or just before rejection, significantly less frequent (P less than 0.01) donor reactive cCTL were found in PBL samples (two out of 20) than in the simultaneously taken EMB samples (13 out of 19). Donor B-LCL and/or third-party B-LCL were lysed by 15 PBL samples. Inhibition studies revealed that this lysis was due to LAK-like cytotoxicity. The results show that peripheral blood does not reflect intra-graft events, which is probably the reason for the irreproducible results of diagnosis of rejection by monitoring immunological parameters in the peripheral blood.

Biopsy↗
PubMed1992

Prevention of cytomegalovirus infection after organ transplantation with passive immunization. An analysis of 6 randomized clinical trials.

We performed a meta-analysis of 6 randomized clinical trials to study the efficacy of passive immunization against CMV in solid organ transplantation. The results indicate that passive immunization against CMV prevents (fatal) CMV disease in CMV seronegative recipients of a CMV seropositive allograft, even when treated with additional immunosuppression in case of rejections. Passive immunization with anti-CMV immunoglobulin preparations did not reduce the incidence of CMV infection or disease in CMV seropositive recipients.

Cytomegalovirus Infections↗
PubMed1991

Blood transfusion induced changes in cell-mediated lympholysis: to immunize or not to immunize.

We have recently observed that the HLA-DR match between recipients and transfusion donors influences the beneficial effect of blood transfusions on allograft survival. To examine the immunologic effects of one-HLA-DR-Ag-matched and completely DR-mismatched transfusions, transfusion-induced changes in cell-mediated lympholysis (CML) were investigated. Blood donor directed CTL activity was measured in vitro before and after blood transfusion in 56 candidates for organ transplantation who received planned HLA-typed blood. We report that blood donor-directed CTL activity increased substantially after a single transfusion mismatched with the recipient for two HLA-DR Ag (p less than 0.0001). A transfusion matched for one HLA-DR Ag did not enhance CTL activity. No correlation was found between CTL reactivity and sharing of HLA class I Ag. The present study supports our previous observation that matching for at least one HLA class II Ag (HLA-DR) between transfusion recipient and blood donor is required if immunization by blood transfusion is to be avoided. These data show that the presence or absence of "autologous" HLA-DR Ag on the leucocytes of the transfusion donor plays a decisive rol whether immunization or immune suppression will ensue.

Blood Transfusion↗
PubMed1991

Phenotypic and functional analysis of T cell receptor gamma delta-bearing cells isolated from human heart allografts.

Endomyocardial biopsies from human heart transplant recipients were investigated with respect to the occurrence of in vivo activated, alloreactive TCR-gamma delta+ cells. More than one year after transplantation, 30% of the biopsy-derived T cell cultures contained TCR-gamma delta+ cells, whereas in the first year after heart transplant in only 8% of the culture TCR-gamma delta+ cells were found. Such an increase of TCR-gamma delta+ cells was not observed in the peripheral blood of the patient. In most biopsy-derived cultures, the gamma delta cells were delta-TCS1+. No donor-specific cytotoxic activity could be demonstrated for TCR-gamma delta+ cells tested, whereas non-MHC-restricted cytotoxicity was found in several cultures. The occurrence of nonalloreactive TCR-gamma delta+ cells late after transplantation, when acute cellular rejection episodes are rare, suggests a role in the down-regulation of the allo-Ir.

Cells, Cultured↗
PubMed1991

Alloreactive lymphoid infiltrates in human heart transplants. Loss of class II-directed cytotoxicity more than 3 months after transplantation.

From 535 endomyocardial biopsies (87 heart transplant recipients) 283 cell cultures could be generated. All cultures tested contained T lymphocytes and in most cases CD4 was the predominant phenotype at any time posttransplant. A significantly higher proportion of CD8-dominated cultures was found among cultures from biopsies without myocytolysis. In the first 3 months post transplant 57% of cultures showed cytotoxicity against both class I and class II mismatched donor major histocompatibility complex (MHC) antigens, changing to an incidence of 33% at greater than 90 days. This proved to be due to a significant decrease in the number of cultures with human leukocyte antigen class II-directed cytotoxicity. This study shows that early after transplantation a heart transplant is infiltrated with activated donor-specific cytotoxic T cells which recognize a broad spectrum of mismatched donor MHC antigens, and that in time this spectrum becomes more restricted.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

[Possibilities and limitations of heterotopic auxiliary liver transplantation].

Although auxiliary heterotopic liver transplantation offers theoretical advantages over orthotopic liver replacement, clinical results have heretofore been dismal. After development of a technique of reduced size liver grafts provided with portal and arterial blood and venous drainage via the suprahepatic V. cava (HLT) in experimental animals, this method was applied in 21 transplantations in 19 patients. 11 of 16 patients with chronic liver insufficiency and one of three patients with fulminant liver failure survived transplantation for at least 1 year. HLT was well tolerated even by high-risk patients. Possibilities and limitations of this novel approach are discussed.

Adult↗
PubMed1990

Rejection prophylaxis with sequential OKT3 and CSA after kidney transplantation.

Sixteen kidney transplant recipients received the IgG2a anti-CD3 monoclonal antibody OKT3 and azathioprine as rejection prophylaxis during the first two postoperative weeks. Concomitant immunosuppression consisted of low dose steroids while cyclosporine A therapy was instituted on day 12. Side effects included fever, bronchospasm, hypotension and diarrhoea. OKT3 caused T cell modulation resulting in CD3 dim+, CD4+ or CD8+, CD5+, WT31- and 11F2- cells. Anti-OKT3 antibodies were found in approximately 50% of the patients. The protocol induced a 100% patient and graft survival and a 81% actuarial freedom of rejection at 18 months. It prevented CsA associated nephrotoxicity in the direct postoperative phase. These beneficial effects outweighed the side effects of OKT3.

Adult↗
PubMed1990

gamma delta T-cell receptor-positive T-cell clones derived from human heart transplants do not show donor-specific cytotoxicity.

gamma delta T-cell receptor-positive T-cell clones were obtained from three endomyocardial biopsies taken from two patients. Clones obtained from two biopsies from patient A, one taken during rejection and one after resolution of this rejection, were WT31-, 11F2+, Ti gamma A-, delta TcS1+. Clones from patient B grown from a biopsy without histologic signs of rejection were either WT31-, 11F2+, Ti gamma A+, delta TcS1-, or WT31+. All gamma delta T-cell receptor-positive clones had cytolytic potential but did not demonstrate donor-specific lysis.

Biopsy↗
PubMed1990

Comparison of four different cyclosporine immunoassays in heart and kidney transplant recipients.

Four different immunoassays were used to measure cyclosporine A (CsA) plasma (20 degrees C) levels in heart and kidney transplant recipients. Two radioimmunoassays (RIAs) (Sandimmune and Cyclotrac) and the fluorescence polarization immunoassay (FPIA) were based on polyclonal antibodies, whereas the fourth (Cyclotrac-SP) used a CsA-specific mouse monoclonal antibody. We found considerable differences in measured CsA concentrations, which were dependent on the method used and the clinical situation of the patient. Correlation coefficients between the nonspecific assays ranged from 0.899 to 0.901 with plasma values increasing in the order Sandimmune less than Cyclotrac less than FPIA. In the CsA-specific RIA, values were lower, and the correlation with the nonspecific assays ranged from 0.761 to 0.795. In the first 21 days posttransplantation, the heart transplant group showed a higher ratio of nonspecific/specific CsA (mean 4.0) compared with the subsequent period (mean 2.3) or with renal transplant recipients (mean 2.4). The TDX method showed the best assay characteristics. In heart transplant patients with specific and nonspecific 125I-RIA methods, mean CsA levels were 25% lower during rejection periods compared with periods without signs of rejection.

Antibodies, Monoclonal↗