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K Wonigeit

Publications and source records attributed to K Wonigeit.

At least 55 records · Page 3Linked to original sources
PubMed1995

Alloreactive natural killer cells in the rat: complex genetics of major histocompatibility complex control.

A major role for the nonclassical major histocompatibility complex (MHC) class I region, i.e. RT1.C, in controlling rat natural killer (NK) cell alloreactivity has recently been established, and several findings suggested the existence of NK-triggering alloantigens coded for by this region. Here, we have extended our studies on the MHC control of NK cell cytotoxicity against concanavalin A-activated T cell blasts by comparing semi-syngeneic and fully allogeneic combinations, and we show the following: (a) The self MHC exerted a strong influence on the NK allorecognition repertoire. (b) When anti-F1 hybrid cytolytic activities of parental strain NK cells were measured, both recessively and non-recessively inherited susceptibility patterns emerged. (c) In most combinations parental strain cells were lysed by F1 hybrid NK cells, thus resembling the hybrid resistance phenomenon described in mice. The cytotoxicity was lower in strain combinations where NK susceptibility was inherited non-recessively, i.e. when parent anti-F1 reactivity was detected, than in recessive combinations. (d) LEW.1LM1 (RT1lm1) target cells, with a deletion in the RT1.C region that includes expressed class I genes, were more sensitive to lysis by MHC matched NK cells (PVG.1L(LEW), RT1l) than were parental LEW (RT1l) cells. The effect of the deletion was the opposite when MHC allogeneic (RT1c, RT1u) as well as semi-syngeneic (RT1l/c) NK cells were employed, i.e. sensitivity was decreased. We conclude that certain MHC-encoded antigens, depending on the haplotype combination of effector and target cells, may either trigger or inhibit rat NK cell cytotoxicity. Furthermore, the potential role of peptides bound to MHC class I molecules recognized by NK cells is discussed.

Alleles↗
PubMed1995

A point mutation in the human CD45 gene associated with defective splicing of exon A.

CD45 is a receptor-type protein tyrosine phosphatase involved in the regulation of lymphocyte activation. Different CD45 isoforms are generated by alternative splicing of three variable exons (A, B and C). The pattern of CD45 splicing depends upon cell type and state of activation. CD45RA isoforms (containing exon A-encoded sequences) can usually be found on a subset of resting T cells, but not on activated T cells. We have recently described a variant pattern of CD45RA expression which is characterized by continuous expression of CD45RA molecules on activated and memory T cells. Here, we demonstrate that this phenotype is associated with heterozygosity for a point mutation at nucleotide position 77 of exon A, leading to a C-->G transition. This mutation does not change the protein sequence of the CD45RA isoform. We conclude that position 77 is part of a motif necessary for splicing of exon A, which supports the hypothesis that sequences within exons have significant effects on alternative splicing. The mutation of this motif might prevent binding of a transacting splice factor. In the heterozygous state, this mutation is not associated with impaired T cell reactivity. Functional consequences of the homozygous state remain to be elucidated.

Base Sequence↗
PubMed1995

Extramedullary erythropoiesis in human liver grafts.

Extramedullary erythropoiesis in the adult is very rare and is generally confined to situations of severe bone marrow irritation or replacement. In this study, we describe the occurrence of intrahepatic erythropoiesis in patients who have received a liver allograft and who have no evidence of bone marrow dysfunction. By routinely performed transplant aspiration cytology (TAC), marked intrahepatic erythropoiesis could be detected in 39 of 312 patients (12.5%) with liver allograft. In 19 patients, including 5 of 8 (63%) after combined liver and kidney transplantation, intrahepatic erythropoiesis occurred within the first 3 weeks after surgery. Twenty patients showed intrahepatic erythropoiesis between 3 weeks and 4 months after transplantation. Erythropoiesis was usually transient, lasting between 1 and 3 weeks. Cytologically, mature as well as immature erythroblasts of GlyA+ CD36+ CD45- phenotype could be detected in the grafts, whereas they were absent in blood; histologically, the cells could be localized to the sinusoids of the liver. There was no clear correlation of preoperative or postoperative hemoglobin levels, graft function, kidney function, and immunosuppressive medication with the presence or absence of erythropoiesis. Moreover, serum levels of erythropoietin (EPO) and stem cell factor (SCF) in patients with and without intrahepatic erythropoiesis in the early postoperative phase did not show significant differences. These findings show that intrahepatic erythropoiesis can occur transiently in human liver allografts and suggest that systemic stimuli as well as local factors may contribute to it.

Biopsy↗
PubMed1995

Early intragraft inflammatory events of liver allografts leading to chronic rejection.

In this retrospective study, we have investigated the early intragraft inflammatory events of 12 liver allografts leading to chronic rejection. The cytological findings and clinical follow-up were analyzed in detail. Nine patients underwent at least one typical lymphoid activation of acute rejection, and three of them were treated more than once. Diagnosis of rejection was based on biopsy histology, cytology and liver dysfunction. In addition to the acute rejections, cytological analysis demonstrated in 11 of 12 grafts an unidentified lymphoid episode that differed from that of rejection. These lymphoid responses were associated with viral infections; cytomegalovirus (CMV) infection in 10 of 12 patients, hepatitis C virus (HCV) infection in 2 of 12 patients, 1 combined with CMV, and hepatitis B virus (HBV) infection in 1 patient. Graft dysfunction was still seen at the end of the follow-up. Thus, intragraft inflammation caused either by acute rejection or by viral infections may be involved in the induction of chronic rejection.

Biopsy, Needle↗
PubMed1995

Influence of bile on cyclosporin absorption from microemulsion formulation in primary liver transplant recipients.

We analysed the absorption, after oral application, of a new galenic form of cyclosporin A (CyA-NOF) in liver-grafted patients (n = 12) during the 1st week (days 2-4) after transplantation. Pharmacokinetic profiling was performed with an open or clamped T tube in situ or with the T tube absent. The pharmacokinetic parameters of CyA-NOF were influenced by T tube clamping and bile diversion. The highest AUC, Cmax and earliest Tmax values were found in patients without a T tube in situ, indicating that absorption of CyA-NOF in patients during the early course after liver transplantation is not bile-independent. CyA-NOF, at a dose of 7.5 mg/kg, was enterally absorbed with appropriate AUC and Cmax levels. Patients receiving a starting dose of 7.5 mg/kg were successfully maintained on CyA-NOF during the subsequent clinical course.

Absorption↗
PubMed1995

Improved absorption of cyclosporin A from a new microemulsion formulation: implications for dosage and monitoring.

Recently, a new oral microemulsion formulation of cyclosporin A (CsA)--Neoral (Sandoz, Basle, Switzerland)--with a higher bioavailability has become available. Ten stable paediatric renal transplant recipients with excessive variations in CsA trough levels with the original Sandimmun (Sandoz, Basle, Switzerland) preparation were switched to Neoral on a 1:1 basis. Pharmacokinetic studies revealed impaired absorption of Sandimmun in six patients. Compared with equal doses of Sandimmun, the 8-h area under the concentration-time curve increased from 1,422 to 2,657 ng x h/ml and the peak concentration rose from 319 to 824 ng/ml (P < 0.01). In six patients with Sandimmun malabsorption, conversion on a 1:1 basis led to a reduction in creatinine clearance which was reversible after dose reduction by 9%-25%. With trough levels at the lower end of the present target range, creatinine clearance stabilised around pre-conversion values.

Adolescent↗
PubMed1995

Immunological effects of the anti-IL-2 receptor monoclonal antibody BT 563 in liver allografted patients.

The immunological effects of therapeutic monoclonal antibodies (mAbs) depend upon their interaction with the target structure as well as the isotype of the mAb which is responsible for the binding to Fc receptors of accessory cells. The aim of the presented analysis was the evaluation of the in vivo immunosuppressive effect of BT 563, a mAb directed to the alpha-chain of the interleukin-2 receptor (IL-2R). Thirty-eight patients following liver transplantation were treated prophylactically for 12 days with 10 mg/day BT 563 (clinical phase II and III study). As baseline immunosuppression cyclosporin (CyA) and low dose steroids were administered. BT 563 levels, lymphocyte subpopulations, levels of soluble CD25 and Fc receptor polymorphism were evaluated and compared to the clinical outcome. Preoperatively in all patients a small subset of CD45R0+ cells expressed CD25 with detectable density. These cells were coated by BT 563. There was no evidence for depletion of IL-2R+ cells or modulation of the IL-2R. During therapy stable levels of the soluble IL-2R were measured in patient sera. Throughout the therapy high levels of unbound BT 563 were found in sera, suggesting that IL-2R newly expressed on cells activated by the allograft could also be inhibited by BT 563. No acute rejections were observed in these patients and no side effects of BT 563 were noted. There were only minor bacterial infections, while mycotic or viral infections did not appear. Administration of BT 563 together with CyA and low dose steroids to liver allografted patients represents a safe and effective protocol. Its action is likely to be mediated by turning off the pathway of signal transduction of the IL-2R in T-cells by the antibody while IL-2 gene transcription is simultaneously modified by CyA and steroids. The addition of all three immunosuppressive mechanisms is suggested to lead to a state of anergy during mAb application that is reversible at the end of antibody therapy but does not lead to rebound rejections. Analysis of the phenotype of CD25+ cells showed that they preferentially belonged to the CD45R0+ cell type. Thus we assume that BT 563 specifically turns off preactivated cells enabling rather selective and effective immunoprophylaxis in liver allografted patients.

Antibodies, Monoclonal↗
PubMed1994

Different cellular patterns associated with hepatitis C virus reactivation, cytomegalovirus infection, and acute rejection in liver transplant patients monitored with transplant aspiration cytology.

Fine-needle aspiration biopsy (FNAB) is a routine diagnostic tool used for the monitoring of the graft during the first postoperative weeks after liver transplantation. The cellular pattern of acute liver rejection is typical in transplant aspiration cytology (TAC), documented and published by several authors. The lymphoid response associated with various viral infections may, however, provide differential diagnostic problems in the cytological monitoring. In this study, we have investigated in detail the cellular pattern of lymphoid response associated with hepatitis C virus (HCV) reactivation, and compared it with the pattern of cytomegalovirus (CMV) infection and with the typical diagnostic findings of acute cellular rejection. HCV reactivation was associated with rather mild total inflammation in the graft (4.5 +/- 1.5 CIU at the peak). The inflammatory infiltrate consisted mainly of small lymphocytes (3.1 +/- 0.2 CIU at the peak), with only occasional activated cells and without lymphoid blast response. No lymphoid activation was seen in the blood. CMV infection was associated with a mild immune response (3.9 +/- 0.4 CIU at the peak) recorded as a slight lymphoid activation and occasional blast cells both in blood and in the graft together with lymphocytosis in the graft (2.4 +/- 0.7 CIU at the peak). The typical findings of acute rejection were easily distinguished from the cellular pictures of both viral infections. The rejections were lymphoid blast (3.6 +/- 3.4 CIU at the peak) and activated lymphocyte (3.5 +/- 2.6 at the peak), dominated by a high peak of total inflammation (9.3 +/- 7.0 CIU). No blast cells and only a few activated cells were seen in the blood during rejection episodes. Thus, the cellular patterns of HCV reactivation and CMV infection differed slightly from each other, but significantly from that of acute liver allograft rejection monitored with the FNAB cytology.

Antibodies, Viral↗
PubMed1994

Control of rat natural killer cell-mediated allorecognition by a major histocompatibility complex region encoding nonclassical class I antigens.

The ability of natural killer (NK) cells to eliminate normal allogeneic hemic cells is well established in several species including mice, rats, and humans. The controlling elements for NK susceptibility in these species map to the major histocompatibility complex (MHC), but in contrast to findings in mice and humans, the mode of inheritance is not always recessive in rats. This finding is not easily explained by the missing self and hemopoietic histocompatibility (Hh) models for NK recognition, and has led to the idea that certain alloantigens may trigger NK cell reactivity. In our in vitro system for assessing rat NK alloreactivity, we have employed target and inhibitor cells from a large panel of MHC congenic, intra-MHC recombinant and MHC mutant rat strains, as well as appropriate F1 hybrids between them, and we show the following: (a) The nonclassical class I (RT1.C) region was most important in determining the susceptibility of target cells to alloreactive NK cells in vitro. Lymphocyte susceptibility to lysis in vivo also mapped to the C region, which supports the concept that the in vivo and in vitro alloreactivity assays reflect the same recognition process. (b) Four different RT1-controlled NK allospecificities (represented by the u, l, a, and n haplotypes) could be discerned when we used polyclonal NK cells from the PVG (RT1c) strain as effector cells. Three of the target specificities recognized were controlled mainly by the RT1.C region. (c) The expression of RT1.C region-controlled parental strain NK allodeterminants could be demonstrated in F1 hybrids heterozygous for the C region alone and were therefore inherited nonrecessively. (d) Loss of an RT1.C region-controlled NK allospecificity could be shown with the MHC mutant LEW.1LM1 rat strain characterized by a genomic deletion of about 100 kb of the C region. Taken together, these observations have demonstrated a major importance of the nonclassical class I region, i.e., RT1.C, in controlling rat NK allorecognition, and have thereby assigned a hitherto undescribed immunological property to this region. Furthermore, some of the present data are consistent with the existence of polymorphic NK-triggering alloantigens that are coded for by the RT1.C region.

Animals↗
PubMed1994

Patterns of donor-type microchimerism after heart transplantation.

Allogeneic microchimerism of donor-type has been demonstrated in stable patients in the long-term after organ transplantation. We have analysed microchimerism in skin and blood of 47 heart-transplanted patients after transplantation with polymerase-chain-reaction amplification specific for donor HLA-DRB1. Microchimerism was detectable in 50% of the patients in the first 6 months, in 100% between 6 months and 2 years, and in 58% in the third postoperative year or later. The state of chimerism was not related to acute or chronic rejections. Patterns of microchimerism after heart transplantation may be dynamic, but any association with clinical and immunological variables remains to be elucidated.

Gene Amplification↗