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G Opelz

Publications and source records attributed to G Opelz.

At least 55 records · Page 3Linked to original sources
PubMed1999

IgA class antibodies and flow cytometric cross-matching in renal transplantation.

BACKGROUND: The established method of pretransplant cross-matching does not detect IgA antibodies, and IgA antibodies have thus been ignored when assessing patients for transplantation. The aim of this study was to detect IgA allo- and autoreactive antibodies using flow cytometry and to correlate the results with transplant outcome. METHODS: Pretransplant sera from 231 sequential renal recipients were tested for serum IgA levels and antibodies directed against the Fab portion of the human IgG molecule. Fifty-nine recipients with sufficient stored donor lymphocytes were also tested by flow cytometry for donor-specific alloantibodies of the IgA isotype. RESULTS: Graft survival was improved in recipients with higher IgA levels. High IgA anti-Fab levels led to a significantly higher 1-year graft survival (P<0.05). Graft survival was further enhanced where both serum IgA and IgA anti-Fab were raised (P<0.01). Although the mean IgA level tended to be higher for recipients with a positive IgA flow cytometric cross-match (FCXM), the IgA FCXM was not associated with increased IgA anti-Fab, suggesting that the IgA FCXM is detecting a different subset of IgA reactivity. Additionally, for primary grafts, a positive IgA FCXM was not associated with enhanced graft survival. CONCLUSIONS: Within the repertoire of IgA activity, there are two recognizable groups, the IgA anti-Fab specificity, which is significantly associated with enhanced graft survival, and that detected by the IgA FCXM, which surprisingly is more likely to be positive in less sensitized first grafts and is not associated with enhanced graft survival.

Flow Cytometry↗
PubMed1999

A combination study design to examine mycophenolate mofetil (MMF) and PTLD in renal transplant patients.

Renal transplant recipients who are chronically immunosuppressed by drugs are at a higher risk of developing malignancies. Commonly observed malignancies are several forms of posttransplant lymphoproliferative disorders (PTLD), skin, lip and gynaecological cancers. The risk is associated with many risk factors including the extent of immunosuppression. Mycophenolate mofetil (MMF) is an immunosuppressant, indicated for the prophylaxis of organ rejection in patients receiving allogenic renal and heart transplants. During the European approval of MMF for renal transplantation, the question was raised as to whether the use of MMF was associated with an increased risk of PTLD in comparison with alternate immunosuppressive regimens. In response, F. Hoffman-La Roche Ltd set up a prospective observational cohort study with a companion case-control study. This paper describes the objectives and the methods of these studies along with the rationale of the methodology.

Journal Article↗
PubMed1999

P-glycoprotein expression is not a useful predictor of acute or chronic kidney graft rejection.

Because of the role of P-glycoprotein (P-gp) in multidrug resistance (MDR), it has been suggested that P-gp might play a role in acute and chronic rejection after organ transplantation. The purpose of the present work was to investigate a possible relationship between graft outcome and P-gp expression on peripheral mononuclear cells of renal transplant recipients. We determined P-gp expression in 27 patients with long-term, stable graft function (ST) and in 15 patients with chronic deterioration of graft function (CR). In addition, 40 patients were studied prior to, and at intervals after, transplantation with 21 healthy individuals serving as controls. P-gp values were highest in healthy controls and in ST patients. We found no correlation between P-gp values and acute rejection. CR patients tended to have lower levels of P-gp expression. Our results contradict the opinion that an overexpression of P-gp induces acute or chronic rejection by inhibiting the efficacy of immunosuppressive treatment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

The antigen binding domain of non-idiotypic human anti-F(ab')2 autoantibodies: study of their interaction with IgG hinge region epitopes.

In previous studies we described a natural human IgG-anti-F(ab')2 autoantibody family with immunoregulatory properties. Genes coding for the variable regions of the heavy and light chains of the Abs were isolated from a natural Ig gene library and scFv Abs were expressed in E. coli. The scFv Abs bound to F(ab')2 but not to Fab fragments. This points to an epitope located in the hinge region since Fab fragments are lacking most of the hinge. In order to verify our hypothesis, double chain peptides comprising the lower-, middle-, and part of the upper hinge subregion of IgG1-IgG4 were synthesized on cellulose membranes and tested for binding to the Abs. The results show binding of Abs to IgG1 and IgG4 hinge region peptides. In order to identify the key residues of the discontinuous epitopes we carried out complete substitutional analyses in which each amino acid of the wt peptides was substituted by all other amino acids except cysteine. The exchange of proline in the IgG1 or IgG4 middle hinge region abrogated the binding, revealing the importance of this subregion for epitope expression. No binding to the IgG2 or IgG3 hinge was detected. These results indicate that scFv anti-F(ab')2 Abs recognize the hinge region of IgG1 and IgG4 and that the expression of the epitope depends on an intact middle hinge subregion.

Amino Acid Sequence↗
PubMed1999

High-resolution typing for HLA-DRB1*15 amd -DRB1*16 by fluorescence-marked sequence-specific priming (TaqMan assay).

Sequence-specific primed polymerase chain reaction (PCR-SSP) is widely used in HLA laboratories. The TaqMan method, which is described here for high-resolution typing of HLA-DRB1*15 and -DRB1*16, does not require elaborate and time-consuming post-PCR detection steps. In this one-tube assay, conventional PCR-SSP and fluorescence detection of the amplicon with a doubly labeled fluorescent probe are combined: a fluorogenic hybridization probe (FHP) labeled with a spectral resolvable fluorescent reporter dye (FAM or TET) at its 5' terminus and a common quencher dye (TAMRA) at its 3' terminus is cleaved by the 5' nuclease activity of Taq DNA polymerase only if the target sequence is amplified. An increase of fluorescence intensity indicates a successful amplification. For high-resolution typing of HLA-DRB1*15 and -DRB1*16 alleles we designed two FHPs and 14 specific primer mixes (7 for DR15 and 7 for DR16). Amplification of the specific sequence was detected by a FAM-labeled FHP, whereas amplification of the internal control was detected by a TET-labeled FHP. We were able to type all heterozygous DRB1*15/DRB1*16 subtype combinations. For evaluation, 60 HLA-DRB1*15-positive and 40 HLA-DRB1*16-positive individuals were typed and the results were compared with conventional PCR-SSP DR15/16 subtyping. There were no discrepancies between the two methods. The TaqMan method is an alternative to conventional PCR-SSP typing which is suitable for routine use in HLA laboratories.

DNA Primers↗
PubMed1999

CD4 depletion in HIV-infected haemophilia patients is associated with rapid clearance of immune complex-coated CD4+ lymphocytes.

The predominant immunological finding in HIV+ haemophilia patients is a decrease of CD4+ lymphocytes during progression of the disease. Depletion of CD4+ lymphocytes is paralleled by an increase in the proportion of immune complex-coated CD4+ cells. We examined the hypothesis that the formation of immune complexes on CD4+ lymphocytes is followed by rapid clearance of immune complex-coated CD4+ lymphocytes from the circulation. In this study, the relationship of relative to absolute numbers of immune complex-loaded CD4+ blood lymphocytes and their association with viral load were studied. Two measurements of relative and absolute numbers of gp120-, IgG- and/or IgM-loaded CD4+ lymphocytes were analysed in HIV+ and HIV- haemophilia patients, with a median interval of approx. 3 years. Immune complexes on CD4+ lymphocytes were determined using double-fluorescence flow cytometry and whole blood samples. Viral load was assessed using NASBA and Nuclisens kits. Whereas the proportion of immune complex-coated CD4+ lymphocytes increased with progression of the disease, absolute numbers of immune complex-coated CD4+ lymphocytes in the blood were consistently low. Relative increases of immune complex-coated CD4+ blood lymphocytes were significantly associated with decreases of absolute numbers of circulating CD4+ lymphocytes. The gp120 load on CD4+ blood lymphocytes increased in parallel with the viral load in the blood. These results indicate that immune complex-coated CD4+ lymphocytes are rapidly cleared from the circulation, suggesting that CD4+ reactive autoantibodies and immune complexes are relevant factors in the pathogenesis of AIDS. Relative increases of immune complex-positive cells seem to be a consequence of both an increasing retroviral activity as well as a stronger loading with immune complexes of the reduced number of CD4+ cells remaining during the process of CD4 depletion. The two mechanisms seem to enhance each other and contribute to the progressive CD4 decrease during the course of the disease.

Antigen-Antibody Complex↗
PubMed1999

HLA compatibility and organ transplant survival. Collaborative Transplant Study.

The influence of HLA compatibility on organ transplant survival was analyzed in more than 150,000 recipients transplanted from 1987 to 1997 at transplant centers participating in the Collaborative Transplant Study. A statistically highly significant effect of HLA matching on graft and patient survival rates was found in the analysis of kidney transplants (P < 0.0001). Ten years after transplantation, the graft survival rate of first cadaver kidney transplants with a complete mismatch (6 HLA-A+B+DR mismatches) was 17% lower than that of grafts with no mismatch. During the first post-transplant year, the class II HLA-DR locus had a stronger impact than the class I HLA-A and HLA-B loci. During subsequent years, however, the influence on graft survival of the three loci was found to be equivalent and additive. For optimal graft outcome, compatibility at all three HLA loci is, therefore, desirable. The excellent correlation of HLA matching observed in recipients of cadaver kidneys with very short ischemic preservation (0-6 hours) or recipients of kidneys from living unrelated donors contradicts reports that short ischemia can eliminate the influence of matching. Although HLA has a significant effect on graft outcome regardless of the state of presensitization, the matching effect is potentiated in patients with highly reactive preformed lymphocytotoxic antibodies. Among first cadaver transplant recipients with an antibody reactivity against > 50% of the test panel, the difference in graft survival at 5 years between patients with 0 or 6 mismatches reached 30%. A collaborative project, in which molecular DNA typing methods were employed, showed that the correction of serological HLA typing errors by more accurate DNA typing results in a significantly improved HLA matching effect. Moreover, matching for the class II locus HLA-DP, a locus that can be typed reliably only by DNA methods, showed a significant effect in cadaver kidney retransplants, especially in the presence of preformed lymphocytotoxic antibodies. The analysis of heart transplants showed a highly significant impact of HLA compatibility on graft outcome (P < 0.0001). This result is of particular interest because donor hearts are not allocated according to the HLA match. A biasing influence of donor organ allocation (i.e. a preferential allocation of good matches to good risk recipients) can, therefore, be excluded. In liver transplantation, neither matching for HLA class I nor HLA class II could be shown to influence transplant outcome.

Graft Survival↗
PubMed1998

The new Eurotransplant Kidney Allocation System: report one year after implementation. Eurotransplant International Foundation.

BACKGROUND: Upon the availability of a cadaveric donor kidney, a delicate allocation process precedes every transplantation. A remodeled Eurotransplant Kidney Allocation System (ETKAS)-derived from simulation studies-was installed in March 1996. The purpose was to adjust long waiting times and international exchange balances, while aiming at an optimal HLA-mismatch distribution. The new ETKAS consisted of a point-score system that was 100% patient oriented. METHODS: The impact of the new ETKAS on the composition of the waiting list, and the outcome of the allocation procedures during its first year, were evaluated and compared with the results obtained in 1995. RESULTS: The percentage of long-waiting patients and of patients with poorly matchable HLA phenotype increased significantly, from 9% to 19% and from 19% to 29%, respectively. Zero HLA-A-, HLA-B-, HLA-DR-mismatched patients still comprised 23% of the kidney transplant activity. The kidney exchange of the different Eurotransplant countries became balanced within 4 months; this persisted during the rest of the year. Pediatric patients had a high transplantation rate due to an assignment of extra points. The composition of the waiting list showed, after 1 year, fewer long-waiting patients and fewer patients with rare HLA phenotypes. CONCLUSIONS: The new ETKAS was able in its first year to meet the goals set at its introduction. In comparison with the old ETKAS, there was a better trade-off between HLA matching and waiting time. The value of computer simulation studies has been demonstrated impressively in the context of organ allocation.

Cadaver↗
PubMed1998

Circulating interleukin-1 receptor antagonist (IL-1RA) serum levels in patients undergoing orthotopic heart transplantation.

In a pilot study we determined the serum levels of circulating interleukin-1 receptor antagonist (IL-1ra) in patients undergoing orthotopic heart transplantation and in control patients scheduled for open heart surgery without allograft transplantation. Blood samples were obtained from 12 transplant recipients and 7 controls prior to the operative procedures to determine baseline values. Serum levels of IL-1ra were measured within 12 h of decrossclamping of the aorta and every 24 h for the following 14 days. Endomyocardial biopsies were obtained weekly for the 1st month after transplantation. Compared to baseline values, IL-1ra serum levels 12 h after decrossclamping of the aorta were significantly higher both in the control group (507 +/- 165 vs 3980 +/- 452 pg/ml, P < 0.01) and among the transplant recipients (413 +/- 180 vs 4117 +/- 459 pg/ml, P < 0.01) IL-1ra levels remained significantly elevated for 2 and 5 days, respectively. There were no significant differences in the IL-1ra serum levels between the two groups throughout the observation period. Endomyocardial biopsies of two patients showed acute allograft rejection, Billingham grade IIIa and IIIb, respectively. In both cases, the rejection episodes were accompanied by a renewed and more pronounced elevation in the IL-1ra serum levels beyond 4000 pg/ml for at least 2 days. These preliminary results indicate that IL-1ra may be a nonspecific immune marker during the first few days after orthotopic heart transplantation and cardiopulmonary bypass. Moreover, renewed, prolonged increases in IL-1ra appear to be associated with rejection. Further studies are needed to confirm the predictive value of IL-1ra in the detection of acute allograft rejection.

Biomarkers↗
PubMed1998

Superior 3-year kidney graft function in patients with impaired pretransplant Th2 responses.

In a prospective study of 80 patients, we investigated the association of kidney graft rejection with pretransplant CD4 helper/suppressor function, B cell responses, and in vitro cytokine secretion. A pokeweed mitogen-driven allogeneic coculture system was used to assess CD4 helper/suppressor function and T cell-dependent B cell responses. SAC I was used for T cell- and monocyte-independent stimulation of B cell cultures. B cell differentiation was assessed in a reverse hemolytic plaque assay. ELISAs were used to determine in vitro cytokine secretion. None of the 12 patients with pretransplant CD4 helper defects (< 10% helper activity) had acute rejection episodes in contrast to 32 of 68 (47%) patients with normal pretransplant CD4 helper function (P = 0.001). Patients with pretransplant CD4 helper defects exhibited better 3-year graft function than patients without CD4 helper defects (serum creatinine of functioning grafts: 1.2 +/- 0.1 mg/dl compared to 1.7 +/- 0.1 mg/dl, P < 0.05). Low pretransplant IL-10 responses (< 100 pg/ml; 14/80 patients) were significantly associated with a low incidence of acute rejection episodes (P < 0.01) and good 3-year graft function (P < 0.05). These data show that impaired pretransplant Th2 responses-CD4 help and IL-10 responses-predict a low risk of kidney graft rejection and good 3-year graft function, whereas Th1 (IL-2, IFN-gamma) and B cell/monocyte responses are not of predictive value.

B-Lymphocytes↗
PubMed1998

Factors relevant for the induction of rejection by indirect recognition in a rat heart allograft model: effect of CTLA4Ig treatment on indirect alloactivation induced by immunization with donor MHC I peptides.

We have defined factors relevant for the induction of rejection by indirect recognition in a rat heart allograft model and analyzed the influence of CTLA4Ig treatment on indirect alloactivation induced by donor MHC I peptides in a DA-->LEW heart allograft model. Indirect allorecognition of MHC I led to accelerated graft rejection and was accompanied by the induction of anti-peptide antibodies and donor peptide-activated T cells. In an attempt to block the B7-induced costimulatory signal of T cell activation, CTLA4Ig was administered to graft recipients in addition to MHC I peptide treatment. CTLA4Ig therapy, however, was not effective in preventing the humoral or cellular anti-donor immune response, nor did it prevent accelerated graft rejection.

Abatacept↗