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V Kiefel

Publications and source records attributed to V Kiefel.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Fc receptor-dependent platelet activation results independently of glycoprotein complex IIb/IIIa].

Platelets of a patient with Glanzmann's thrombasthenia revealed the same activation pattern when stimulated with antibodies of patients with heparin-associated thrombocytopenia (HAT) or immune complexes. This was investigated by the 14C-serotonin release test and by changes in phosphorylation of p20 and p47. Platelet activation by HAT antibodies was completely inhibited by a moab against the platelet FcRII (IV. 3) and by Fc fragments of human IgG but not by F(ab)2 fragments. We conclude that platelet activation via the FcRII occurs independently of the glycoprotein complex IIb/IIIa. Therapeutical approaches targeting GP IIb/IIIa-fibrinogen interaction seem to be not appropriate in HAT.

Blood Platelets↗
PubMed1994

[Comparison of serologic typing and DNA typing of platelet alloantigens].

Platelet alloantigens of the Zw, Ko, Bak und Br systems were determined by restriction fragment length polymorphism (RFLP) analysis of appropriate PCR products in 98 unselected patients. Results were compared with serological typing by monoclonal antibody immobilization of platelet antigens (MAIPA) and platelet agglutination.

Agglutination Tests↗
PubMed1994

[Molecular biologic clarification of Br alloantigens in human platelets and its application in DNA typing].

Alloimmunization against the platelet alloantigen Br (HPA-5) is the second most common cause of neonatal alloimmune thrombocytopenia (NAIT) in Caucasian populations. We have recently shown that a single-base polymorphism at position 1648 on platelet mRNA coding for GPIa results in an amino acid substitution at position 505 on the mature glycoprotein Ia which is associated with the two serologically defined Br phenotypes. To establish DNA-based genotyping for the Br system we elucidated the genomic organization of the GPIa gene adjacent to the polymorphic base. Using PCR of blood cell DNA we have identified a 144 bp exon encoding the Br polymorphic base. A PCR primer based on the 3' intron sequence of this exon in combination with an exon-primer was used to amplify a 274 bp fragment of the GPIa gene. Restriction analysis using the endonuclease Mnl I leads to a Br-specific restriction fragment length polymorphism (RFLP) which perfectly correlates with serological phenotyping.

Antigens, Human Platelet↗
PubMed1994

[Effect of HPA-1a(PLA1) and HLA antibodies on platelet function, measured with the in vitro bleeding test].

The influence of platelet-specific and HLA antibodies on primary hemostasis was investigated by the in vitro bleeding test (IVBT). Seven of 12 plasmas with HPA-1a (PLA1) antibodies and two with antibodies against glycoprotein Ib/IX significantly inhibited the IVBT of normal cross-match-positive donor blood. This correlated with an increase of GMP-140 on the platelets determined by flow cytometry. Therefore the inhibition of the IVBT was interpreted to be due to rapid platelet activation by platelet-specific antibodies followed by an irreversible loss of function. In contrast, with HLA antibodies neither activation nor inhibition of the platelet function could be proven.

Antigens, Human Platelet↗
PubMed1994

[A single base substitution is responsible for the origin of "private" platelet Sra antigens affects molecular weight polymorphism of glycoproteins IIIa].

Some of the genetic polymorphisms of the platelet membrane glycoproteins (GP) IIIa are known to be responsible for alloantibody formation (Zw, Yuk). These antibodies may be involved in neonatal alloimmune thrombocytopenia, posttransfusion purpura, and sometimes in the state of refractoriness to platelet transfusion. Recently we described the first 'private' alloantigen on platelets residing on the 66-kDa membrane-bound fragment of GP IIIa. Further molecular genetic studies showed that the Sr polymorphism is associated with a C to T substitution at base 2004 in the GP IIIa gene resulting in an Arg/Cys amino acid dimorphism at position 636. Transfection of COS cells with recombinant forms of GP IIIa cDNA demonstrated that this amino acid dimorphism is responsible for the formation of the Sra epitope. Furthermore, the Sra variant of GP IIIa showed a slightly increased molecular weight which is presumably caused by different glycosylation.

Antigens, Human Platelet↗
PubMed1994

[Two modifications of MAIPA assays for the demonstration of platelet antibodies].

The monoclonal antibody immobilization of platelet antigens assay (MAIPA), published in 1987, is now used by many laboratories for detection of platelet antibodies. False-positive results were observed with sera containing anti-mouse IgG and in cases where MAIPA was employed to characterize platelet-specific antibodies of the IgM class. Modifications of MAIPA which completely eliminate these artifacts are described.

Animals↗
PubMed1994

[Anti Ko(a) as a cause of neonatal alloimmune thrombocytopenia].

Neonatal alloimmune thrombocytopenia (NAIT) is caused by maternal immunization against a paternal antigen on fetal platelets. The antigens mostly involved are Zwa (PlA1) and Br(a). The Ko alloantigen system which is localized on the N-terminal region of glycoprotein Ib usually causes antibody formation in polytransfused patients but is only rarely implicated in NAIT. Ko(a) antibodies raised in the mother of a thrombocytopenic newborn were shown to be detectable by platelet agglutination and MAIPA assay if the antigen-bearing N-terminal glycocalicin is protected from proteolytic degradation.

Antigens, Human Platelet↗
PubMed1994

[Immunization against a new, infrequent alloantigen (Iy) on the platelet glycoprotein Ib/IX as a cause of a serious case of neonatal alloimmune thrombocytopenia].

Neonatal alloimmune thrombocytopenia is the consequence of maternal alloimmunization against platelet-specific alloantigens, usually PIA1 or Br(a). The clinical picture is characterized by signs of haemorrhagic diathesis as a result of marked thrombocytopenia. In the last years, rare cases of immunization against 'low-frequency' or 'private' platelet alloantigens on the platelet glycoprotein (GP) complex IIb/IIIa have been found. This is the first report on NAIT due to maternal immunization against a low-frequency platelet alloantigen ('Iy') localized on platelet GP Ib/IX.

Antigens, Human Platelet↗
PubMed1994

[Prenatal substitution therapy in fetal alloimmune thrombocytopenia].

Fetal alloimmune thrombocytopenia is caused by maternofetal transfer of platelet antibodies. Since the thrombocytopenic fetus is threatened by intracranial hemorrhage, prenatal observation and, if necessary, treatment is required. However, the benefit of therapeutic options, including intravenous IgG (ivIgG) or platelet transfusions, is still controversial. In this study we have evaluated the effect of maternal ivIgG and intraumbilical platelet transfusions on fetal platelet counts in 7 cases. All patients were multiparous women who were immunized against the Zwa antigen during previous pregnancies and had given birth to at least one severely thrombocytopenic infant. First umbilical blood was sampled at the 26th week of gestation. Maternal treatment of ivIgG was given over 7 weeks, the mean number of intrauterine platelet transfusions was 5.9. In 6 of 7 cases the basal platelet count before transfusion did not rise or even further decreased during maternal ivIgG treatment. In one case the baseline platelet count increased from 18,000/microliter to 60,000/microliter during ivIgG. We conclude that, in general, ivIgG alone has no detectable effect on fetal alloimmune thrombocytopenia. Since platelet counts can be very low as early as 20 weeks of gestation, careful fetal monitoring by umbilical blood sampling is required. Platelet transfusions in short intervals appear to be the only effective regimen to increase platelet counts in extremely thrombocytopenic fetuses.

Antigens, Human Platelet↗
PubMed1993

Immune thrombocytopenia associated with hemorrhagic diathesis due to ibuprofen administration.

Acute thrombocytopenic purpura temporally related to the oral administration of ibuprofen developed in a patient with ankylosing spondylitis. Clinical manifestations, with sudden onset occurring within 12 h of drug ingestion and rapid increase of platelet counts following discontinuation of the drug, were characteristic of an antibody-mediated immune pathomechanism. Immunological studies demonstrated IgM and IgG antibodies in the patient's serum that were capable of binding to allogenic platelets in the presence of a metabolite preparation. This finding suggested that an ibuprofen metabolite, rather then the drug itself, was the antigenic agent responsible for the immune reaction. Despite its widespread therapeutic use, ibuprofen has not been described previously as causing immune-mediated thrombocytopenia.

Aged↗
PubMed1993

Report on the Fifth International Society of Blood Transfusion Platelet Serology Workshop.

The Fifth International Society of Blood Transfusion (ISBT) Platelet Serology Workshop took place in 1990. A total of 21 laboratories participated in the wet workshop. Results were discussed at a meeting of the International Committee on Standardization in Haematology (ICSH) Expert Panel on Platelet Serology at the Joint Congress of the ISBT and the American Association of Blood Banks in Los Angeles in November 1990. Each of the participants analyzed 37 serum samples for platelet-reactive alloantibodies and isoantibodies. In addition, two drug-dependent (quinine) platelet-specific antibodies had to be identified among a subset of seven sera. For the first time in a platelet serology workshop, five platelet suspensions had to be typed for the alloantigens of the HPA-1, -3, -4, and -5 systems.

Antibodies↗
PubMed1993

Frequency of platelet-specific antigens among Indonesians.

This study reports the frequencies of the alloantigens of four major platelet-specific alloantigen systems among Indonesians. One hundred and sixty-eight unrelated Indonesian blood donors were phenotyped for the alloantigens of the Zw (PIA, HPA-1), Bak (HPA-3), Yuk (Pen, HPA-4), and Br (HPA-5) systems by use of a glycoprotein-specific immunoassay. All were positive for the alloantigens Zwa, Yukb, and Brb. Three (1.79%) and 1 (0.59%) of the 168 donors were positive in testing for Zwb and Yuk(a) antigens, respectively. Fifteen (9.26%) of 162 Indonesians had Br(a) antigens. Of the 166 donors tested, 121 (72.89%) were Bak(a) positive and 134 (80.72%) were Bakb positive. In addition, the phenotype frequency of Nak(a) was determined by using monoclonal antibody OKM5 in a platelet enzyme-linked immunosorbent assay. Its frequency in the present cohort was 95.83 percent (161/168). This study confirms the differences in platelet antigen distributions in Asians and whites. Both glycoprotein IV deficiency and the Yuk polymorphism are also found among Indonesians.

Antigens, Human Platelet↗
PubMed1993

The presence of messenger RNA for HLA class I in human platelets and its capability for protein biosynthesis.

In order to determine whether platelets contain specific messenger RNA encoding for HLA class I molecules, polymerase chain reaction (PCR) was performed with RNA from different platelet donors. Two amplified 300 bp and 279 bp cDNA fragments were obtained which encompassed sequences from 321 to 620 and from 795 to 1073. The 300 bp fragment encodes exon 2 and exon 3, the 279 bp encodes a portion of exon 4, exon 5, exon 6 and a portion of exon 7. A 300 bp nested PCR product from one donor, that encoded for the highly polymorphic region alpha 2, was cloned and sequenced. The resulting nucleotide sequences fitted to the expected sequence for HLA B*3801 of this donor. Sequence analysis of the 279 bp PCR product demonstrated the presence of exon 5 encoding for the 117 bp transmembrane domain. In addition, de novo protein biosynthesis was studied by radioimmunoprecipitation of HLA class I molecules from 35S-methionine metabolically labelled platelet lysates with a monoclonal antibody (mab) w6/32 specific for a monomorphic epitope on the heavy chain of HLA class I antigens. Analysis of the immunoprecipitates on SDS polyacrylamide gel electrophoresis showed a specific band with apparent molecular weight (M(r)) of 44 kD corresponding to integral membrane HLA protein. On the basis of these results, we conclude that platelets contain specific messenger RNA encoding for HLA class I molecules and have the capability to synthesize the integral HLA membrane protein.

Base Sequence↗
PubMed1993

Analysis of granulocyte-reactive antibodies using an immunoassay based upon monoclonal-antibody-specific immobilization of granulocyte antigens.

To detect human granulocyte-reactive antibodies, a glycoprotein-specific enzyme immunoassay for platelet antibodies was adapted for the use of granulocytes as target cells. Peripheral blood granulocytes were simultaneously incubated with a monoclonal antibody (mAb) and the serum to be investigated. After solubilization, aliquots of the cell lysate were transferred to plastic tubes coated with goat anti-mouse antibodies. Following immobilization of the trimolecular (mAb-glycoprotein-human antibody) complex it was detected by addition of enzyme-labelled goat anti-human antibodies using a luminescence technique. This assay allowed identification of different granulocyte-reactive antibodies present in the same sample without the need for complicated absorption studies. Alloantibodies against HLA and the granulocyte-specific NA antigens as well as isoantibodies against the Fc-gamma-receptor III (FcRIII) were detectable using mAb-specific immobilization of granulocyte antigens (MAIGA). Binding of autoantibodies to the FcRIII and to the CD 11b/CD18 complex could be shown.

Animals↗