Biomedical subjects

C Mueller-Eckhardt

Publications and source records attributed to C Mueller-Eckhardt.

At least 127 records · Page 7Linked to original sources

PubMed1990

[The Br(a)/Br(b) alloantigen system in thrombocytes].

Platelet specific alloantibodies cause neonatal alloimmune thrombocytopenia (NAIT), posttransfusion purpura (PTP) and may be found in patients who are refractory to HLA-matched platelet transfusion. Most platelet alloantigen systems comprise two alleles: Zw(a)/Zw(b), Ko(a)/Ko(b), Bak(a)/Bak(b), Yuk(a)/Yuk/b). The corresponding antibodies are detected with the platelet immunofluorescence test, radioimmunoprecipitation, immunoblot, and with a glycoprotein-specific immunoassay. Epitopes of the Zw-, Bak-, and Yuk-alloantigen systems are localized on the GPIIb/IIIa complex. Recently, we characterized antibodies against two alleles of a new alloantigen system (Bra/Brb). Anti-Bra is the second most important antibody to cause NAIT, following Anti-Zwa. Anti-Brb was found in three polytransfused patients. The Br-antibodies may be detected using a glycoprotein-specific enzyme immunoassay (MAIPA assay) and radioimmunoprecipitation. The frequency of the Br-phenotypes in our population is Br(a+b-) 1%, Br(a+b+) 20%, Br(a-b+) 79%. The number of binding sites for Anti-Bra is 2000/platelet on homozygous and 1000/platelet on heterozygous platelets. The Br-alloantigens are localized on GPIa, which is identical with the alpha chain of VLA-2 on activated T-lymphocytes.

Antigens, Human Platelet↗

PubMed1990

[Sr(a), a "private" thrombocyte alloantigen as a cause of neonatal alloimmune thrombocytopenia].

Neonatal alloimmune thrombocytopenia (NAIT) is caused by maternal immunization against fetal platelet antigens. In the serum of a mother who gave birth to a child with the typical clinical picture of NAIT we found an antibody directed against the new platelet antigen Sra. Anti-Sra was found to react in the immunofluorescence test and in a glycoprotein (GP) specific immunoassay (MAIPA) using a monoclonal antibody against GP IIb/IIIa for antigen immobilization with the child's and father's platelets. Radioimmunoprecipitation and immunoblot allowed to assign the Sra-antigen to GP IIIa. The phenotype frequency was estimated less than 1%, characterising the Sra-antigen as the first 'private' alloantigen on platelets.

Blood Platelets↗

PubMed1990

[Serologic characterization of platelet-associated IgG and its significance for the diagnosis of thrombocytopenias].

Detection of platelet autoantibodies in patients with autoimmune thrombocytopenic purpura (AITP) is a notoriously difficult task. The quantitative measurement of PAIgG is rather unreliable as a diagnostic procedure because it tends to yield false positive results in thrombocytopenic patients. In this study two different techniques allowing discrimination of platelet autoantibodies and unspecific IgG bound to the patients' autologous platelets were compared to the quantitative measurement of PAIgG in thrombocytopenic patients. These two techniques are: 1. investigation in the platelet adhesion immunofluorescence test of eluates prepared from the patients' platelets and 2. detection of platelet autoantibodies on the isolated glycoprotein complexes IIb/IIIa, Ib/IX, and Ia/IIa. Results show that positive results with these two techniques are much more specific for autoimmune thrombocytopenia than elevated amounts of PAIgG measured on whole platelets.

Autoimmune Diseases↗

PubMed1990

[219 Zw(a) positive mothers of children with clinically suspected neonatal alloimmune thrombocytopenia].

The sera of 219 Zwa-positive mothers who gave birth to children with clinically suspected neonatal alloimmune thrombocytopenia (NAIT) were tested for platelet-reactive antibodies using the platelet adhesion immunofluorescence test and a glycoprotein-specific immunoassay (MAIPA). In 102 families a serological crossmatch of maternal serum against paternal platelets was performed. 12 sera contained platelet specific antibodies: Zwb (1), Bra (4), Bra and HLA (5), Baka and HLA (1), Sra (1); three further sera contained antibodies against blood group A (1), blood group B (1), blood group B and HLA (1). Anti-Bra was the most important antibody in this cohort. There is evidence that in certain cases antibodies against blood group antigens A or B may cause NAIT. Clinical data of NAIT duo to anti-Bra suggest a less severe bleeding tendency than in NAIT due to anti-Zwa. The HLA-DRw6 antigen was identified as an immunogenetic marker for the immunization against the Bra-antigen.

Antibody Specificity↗

PubMed1990

[Serologic characterization of granulocyte-specific antibodies in neonatal alloimmune neutropenias].

Serological properties of nine granulocyte specific alloantibodies in maternal sera and sera of the newborns were investigated by granulocyte immunofluorescence, granulocyte agglutination and granulocyte cytotoxicity. In the immunofluorescence assay the reactions were more prominent than in the agglutination assay. Only one antibody yielded a positive reaction in the cytotoxicity assay. Four NA2-, two NA1- and one NB1-antibody could be identified. The immunofluorescence assay showed a mixed pattern with the NB1-antibody, indicating a heterogenous distribution of the NB1-antigen on granulocytes of some donors. In titration studies with heterozygous and homozygous donors a gene-doses-effect was demonstrable.

Agglutination Tests↗

PubMed1990

[Autoimmune hemolytic anemia with temporary weakening of Gerbich antigens].

A third patient with autoimmune hemolytic anemia due to autoantibodies against Gerbich antigens is described. The patient's serum contained strong hemagglutinating antibodies of the IgA plus IgG classes which reacted with all red blood cells (RBC) tested, but not with Gerbich-negative cells. Although the patient was typed as Gerbich-positive, his serum failed to react with his own RBC, and the sensitization of his erythrocytes with autoantibodies was only demonstrable if eluates of his RBC were used. The failure of the autoantibodies to react with autologous RBC at the peak of hemolysis most likely reflects a weakening of Gerbich antigens during the course of autoimmune hemolytic anemia.

Adult↗

PubMed1990

[Preparation of leukocyte-poor thrombocyte concentrates from buffy coat by using a new quadruple bag system].

It has repeatedly been shown that platelet concentrates (PC) can be prepared from buffy coat in guadruple Saline(S)-Adenin(A)-Glucose(G)-Mannitol(M) (SAG-M) systems. Their in vivo and in vitro quality was reported to be excellent and their contamination with leucocytes was 10-20 times lower than in PC prepared from platelet rich plasma. We have confirmed these observations (unpublished results). One particular technical problem which we encountered was the appearance of folds in the satellite bag during the second centrifugation step rendering the purity of the PC quite unpredictable. In collaboration with Biotrans, we have developed a modified quadruple bag (733861100) including a special insert (Heraeus Christ, Osterode, FRG) for the centrifugation rotor which has proved advantageous over existing systems and will be briefly described.

Blood Component Removal↗

PubMed1990

[Quality of thrombocyte preparations from buffy coat or platelet-rich plasma].

One hundred platelet concentrates, fifty prepared from buffy coat and fifty prepared from platelet-rich plasma were examined. In platelet concentrates from buffy coat a lower leukocyte contamination (1.4 +/- 1.2 x 10(7) vs 13.2 +/- 15 x 10(7], a significant higher ATP content (6.3 +/- 1.7 mmol/10(14) platelets vs 3.9 +/- 1.9 mmol/10(14) platelets) and a better response in ADP- or collagen-induced aggregation could be determined during storage of five days. Our results indicate that preparation of platelet concentrates from buffy coat is preferable to their preparation from platelet-rich plasma.

Adenosine Triphosphate↗

PubMed1989

348 cases of suspected neonatal alloimmune thrombocytopenia.

Serological and clinical data were collected in 348 cases of suspected neonatal alloimmune thrombocytopenia (NAT). Of the 144 mothers who were Zwa-negative, 107 had Zwa antibodies--alone (94); with HLA antibodies (12); or with Bra antibodies (1). Antibodies were detected in 12 of the 204 Zwa-positive mothers as follows: anti-Bra (9), anti-Zwb (1), anti-Baka with HLA antibody (1), and blood group B isoagglutinins (1). The frequency of NAT due to Bra incompatibility (19%) was second to Zwa (78%). Zwa-NAT was clinically the more severe (14% had intracranial haemorrhages) and responded well to either maternal platelet transfusions or intravenous IgG. In Bra-NAT intracranial haemorrhages were not observed and most children recovered without specific therapy.

Adolescent↗

PubMed1989

[Antibodies, clinical and hematologic findings in immunoneutropenias].

Sera were analyzed from patients who were suspected to have antibodies to neutrophils. The analysis comprised five methods which avoid heterologous antibodies to human immunoglobulin. These methods were the granulocyte agglutination test (GAT), the granulocyte cytotoxicity test (GCT), the monocyte cytotoxicity test (MCT), the lymphocyte cytotoxicity test (LCT) and immune phagocytosis inhibition test (IPI). Each serum was tested with cells from five healthy donors, at least, and some with cells from relatives. After exclusion of sera containing multiple antibodies and HLA-antibodies with positive LCT- and IPI-tests, the GAT- or GCT-reactive antibodies were significantly (p = 0.00005) more frequent among patients with neutrophil counts less than or equal to 1.0 X 10(9)/l (30%; n = 117) than among patients with neutrophil counts greater than 1.0 X 10(9)/l (9%; n = 111). Within the group of neutropenic patients (less than or equal to 1.0 X 10(9)/l) these antibodies were significantly (p = 0.001) more frequent in patients without (48%; n = 46) than with reduction of the granulopoiesis (13%; n = 31). This typical feature of an immune cytopenia also could be shown with GAT-reactive antibodies alone. From all five antibody tests the diagnostic criteria of the autoimmune neutropenia (AINP) and neonatal alloimmune neutropenia (NIN) were infered. 25 patients with clearly defined AINP presented with significantly more infectious complication than 23 patients with only assumed AINP (48% versus 13%). Further, the clinical findings of eight patients with NIN were described. --Antibodies only reactive in the GAT were detected in healthy individuals (1.3%; n = 75) and patients without indication for AINP or NIN (8%; n = 111), also.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

In vitro fixation of C3d and C5b-9 on platelets by human platelet reactive antibodies.

Most platelet-reactive autoantibodies and alloantibodies are not able to fix complement in vitro. However, exceptions have been found. These antibodies are usually characterized by the conventional platelet complement fixation test. A recently developed competitive enzyme immunoassay for quantitation of platelet-associated immunoglobulins and a modification thereof allowed the quantitative study of fixation of C3d and the membrane attack complex (C5b-9) on platelets by HLA antibodies, human platelet autoantibodies, and drug-dependent antibodies (ddab). The highest amounts of both complement products were fixed through ddabs, whereas autoantibodies only showed moderate complement fixation. This enzyme immunoassay is a valuable tool for the characterization of the complement-fixing properties of platelet-reactive antibodies.

Antibodies↗

PubMed1989

Recent trends in platelet antigen/antibody detection.

The detection of platelet antigens and platelet antibodies has always been difficult. Recent technical achievements are due to the availability of more specific and sensitive reagents (i.e. F(ab)2 fragments; higher specific activity of labels; monoclonal antibodies directed against platelet membrane constituents etc.) and the application of advanced immunological assays to platelet immunology (i.e. blotting assays, "capture"-ELISA's and radioimmunoprecipitation in conjunction with SDS polyacrylamide gel electrophoresis). These techniques have permitted the definition and immuno-chemical characterization of new platelet allo- and autoantigens, have assisted in clinical diagnosis and promoted our understanding of pathogenic mechanisms. Illustrative examples are presented and discussed.

Antibodies↗

PubMed1989

High-dose IgG treatment for neonatal alloimmune thrombocytopenia.

Twelve children with neonatal alloimmune thrombocytopenia (NAT) due to Zwa incompatibility were treated with intravenous IgG (IVIG). Total doses ranged between 1 and 9 g. Ten out of 12 infants had a favorable response. It is concluded that IVIG can serve as an emergency treatment in NAT if material (or compatible) platelets are not available.

Blood Platelets↗

PubMed1989

Identification of the target platelet glycoprotein in autoimmune thrombocytopenia occurring after allogeneic bone marrow transplantation.

We report the case of a patient who developed autoimmune thrombocytopenia after allogeneic bone marrow transplantation from her HLA-identical sister. An IgG autoantibody was detected that bound to the platelet glycoprotein IIb/IIIa and to the HLA class I proteins. Immunoprecipitation studies with radiolabeled platelets revealed additional antibody binding sites on proteins of 214 kDa molecular weight under nonreduced conditions and 65 and 56 kDa molecular weight under reduced conditions.

Adult↗

PubMed1989

Acute immune hemolysis induced by a degradation product of amphotericin B.

We report here on an eight-year-old boy who first developed acute intravascular hemolysis following therapy with amphotericin B (AmB) and subsequently a delayed hemolytic transfusion reaction due to alloantibodies. Although there is as yet no evidence for metabolism of AmB in vivo, the hemolysis appeared to be the result of sensitization against a degradation product of the drug. The patient's serum contained a hemagglutinating IgM antibody that reacted with all red blood cells (RBC) tested in the presence of plasma obtained from patients receiving AmB (ex vivo antigen), but not in the presence of their urine, AmB itself, or with AmB-pretreated RBC. These findings indicate that the antibody was directed against a degradation product of AmB, presumably a trace metabolite, that has not yet been identified.

Acute Disease↗

PubMed1989

Discrimination of antibodies against antigens of different MHC loci in human sera by monoclonal antibody-specific immobilization of leukocyte antigens.

To detect human antibodies against antigens of different major histocompatibility complex loci, particularly of class II specificity, a newly developed enzyme immunoassay for platelet antibodies was adapted for the use of lymphocytes as target cells. Peripheral blood lymphocytes, phytohemagglutinin-stimulated T cells, or Epstein-Barr virus-transformed B cells were simultaneously incubated with a monomorphic class- or locus-specific monoclonal antibody and the human antibody to be investigated. After solubilization, cell lysates were transferred to an enzyme-linked immunosorbent assay tray coated with a goat anti-mouse Ig antibody. Following immobilization of the monoclonal antibody/antigen complexes, human major histocompatibility complex antibodies were detected by addition of enzyme-labeled goat anti-human Ig. By means of this technique human antibodies against different major histocompatibility complex molecules present in the same sample could be clearly distinguished. Application of the monoclonal antibody-specific immobilization of lymphocyte antigens assay is presented by several examples. Of these, identification of DP-specific antibodies as well as serological DP typing are of particular interest.

Antibodies, Monoclonal↗

PubMed1989

Human platelet alloantigens Bra/Brb are expressed on the very late activation antigen 2 (VLA-2) of T lymphocytes.

We report the molecular localization of the human platelet alloantigens Bra/Brb on activated T lymphocytes. By radioimmunoprecipitation anti-Bra precipitated two proteins from T lymphocytes of Br(a+) donors after long-term activation (24 days), but not from resting or short-term-activated T lymphocytes (4 days). No bands could be precipitated with anti-Bra from T lymphocytes of Br(a-) donors, but the same two bands were seen with anti-Brb. The apparent molecular weights of unreduced molecules were 155 and 130 kDa, respectively. Monoclonal antibody Gil4 directed against an epitope on the platelet membrane glycoprotein Ia/IIa complex precipitated the same two bands with long-term-activated T lymphocytes, whereas MoAb TS2/7 directed against very late antigen (VLA)-1 molecules precipitated two bands with Mr 180 and 130 kDa (alpha 1 beta heterodimer). The physicochemical properties of these two bands precipitated by anti-Bra, anti-Brb or monoclonal antibody Gil4 with molecular weights of 155 and 130 kDa, respectively, correspond to VLA alpha 2 and beta chains and fit defined criteria for the VLA-2 antigen. These results were corroborated by an assay employing monoclonal antibody for antigen immobilization showing that Bra and Brb antigens were present only on long-term activated T lymphocytes. Our results provide evidence for the expression of the Bra/Brb platelet alloantigen system on VLA-2 antigens of activated T lymphocytes and demonstrate a genetic polymorphism of VLA-2 molecules on both cell lines.

Antigens, Differentiation↗

PubMed1989

Immune thrombocytopenia more than a year after allogeneic marrow transplantation due to antibodies against donor platelets with anti-PlA1 specificity: evidence for a host-derived immune reaction.

We report on a male patient transplanted from his HLA-matched sister for Ph1-chromosome positive chronic myelogenous leukaemia who developed immune thrombocytopenia more than 1 year after transplantation. The platelet antibody reacted with the platelet specific antigen PlA1 on donor platelets, and also on recipient platelets after engraftment. A presumed host-versus-donor induced thrombocytopenia was supported by Southern blot analysis using a Y-chromosome specific probe demonstrating residual host-origin cells in the patient's excised spleen.

Adult↗