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Biomedical subjects

W R Mayr

Publications and source records attributed to W R Mayr.

At least 91 records · Page 5Linked to original sources
PubMed1995

Risk of human immunodeficiency virus (HIV) transmission by anti-HIV-negative blood components in Germany and Austria.

In order to estimate the residual risk of transfusion-transmitted HIV infection we have analyzed the data from two transfusion centers in Austria (Vienna) and Germany (Göttingen) from 1985 to 1994. In Vienna, an incidence of 1:42,000 positive anti-HIV tests in repeat donors and a prevalence of 1:7000 in first-time donors were found in 1993. In Göttingen, the indicence was 1:67,000 and the prevalence 1:7900 from 1985 to 1993. Based on a mathematical model which takes (a) the window period and (b) the false-negative rate of anti-HIV tests, as well as (c) human and operational errors into consideration, we have calculated the residual risk of HIV infection. The residual risk (third generation anti-HIV test) was found to be 1:520,000 (95% confidence interval 1:1340,000-1:210,000), and 1:900,000 (95% confidence interval 1:2340,000-1:380,000) for Vienna and Göttingen, respectively, in 1993. Look-back studies from 1985 till 1994 revealed transfusion-transmitted HIV infections in three recipients (for 1.9 million donations in Vienna) and one recipient (for 160,000 donations in Göttingen) of blood components. Based on our model, as well as on prevalence and incidence rates of HIV infection, it is also possible to predict the efficacy of additional measures introduced to further decrease the risk of transfusion-transmitted HIV infection through blood components.

Austria↗
PubMed1995

[Therapeutic concepts in transfusion medicine. Report on the 1st Graz "Transfusion Medicine" Consensus Conference].

The safety of blood and blood components is an important aspect of transfusion medicine. Even if absolute safety of blood products cannot be achieved, this goal has come closer due to significant improvements. These include: (1) exact donor registration; (2) component preparation according to legal requirements and GMP guidelines; (3) determination of all relevant diagnostic parameters according to GMP/GLP guidelines; (4) adequate storage of products; and (5) and often underestimated parameter ensuring safety, strict guidelines for the use of blood products in the treatment of patients. Some of the results of the first Graz Consensus Conference on Transfusion Medicine are presented.

Austria↗
PubMed1995

DNA markers in forensic medicine.

After a description of the various DNA polymorphisms which can be used in forensic medicine, the use of these markers for solving cases of disputed paternity is discussed in detail. VNTR polymorphisms detectable after amplification of the relevant loci by the PCR seem to be the best tools for paternity testing.

DNA↗
PubMed1995

Maternal alloimmunization against fetal platelet antigens: a prospective study.

Neonatal alloimmune thrombocytopenia (NAIT) is induced by maternal alloantibodies to fetal platelet antigens. This prospective study was carried out to evaluate the incidence of anti-platelet antibodies in 933 mother-child pairs where the mother and child were typed for the human platelet antigens (HPA)-1, -2, -3, -5. Sera from mismatched mother-child pairs were screened for anti-platelet antibodies, anti-HLA class I and blood group ABO IgG antibodies. Platelet-specific antibodies were anti-HPA-3a in one and anti-HPA-5b in 17 neonates, respectively. All these neonates had normal platelet counts. One woman had autoreactive antibodies. Anti-HLA class I and anti-blood group A IgG antibodies were detected in five and four neonates, respectively, born with a platelet count < 150 x 10(9)/l. None of the 11 homozygous HPA-1b mothers became immunized against their heterozygous offspring. The maternal HLA-allotypes HLA-DR52 and -DR6, typically found in individuals immunized against HPA-1a and -5b, respectively, were found in three of 11 HPA-b/b nonresponders and eight of the anti-HPA-5b responders. The results indicate that a risk for NAIT due to HPA-2 and -3 alloimmunization is low. The HLA allotypes do not predict the risk for NAIT due to HPA-1 or -5 alloimmunization. Maternal anti-HPA-5b antibodies do not correlate with the platelet count in the neonate.

ABO Blood-Group System↗
PubMed1995

Flow cytometric analyses of the subclasses of red cell IgG antibodies.

We report on flow cytometric IgG subclass determinations of red cell antibodies using polyclonal FITC-labeled antibodies. The limit of detection of this method was 1 ng anti-D per 1 x 10(7) red cells. The inter- and intra-assay coefficients of variance were 8.2 and 2.3%, respectively. In 8 newborns with a positive direct antiglobulin test (DAT) in the gel centrifugation test (GCT), due to ABO antibodies, IgG1 was detected in all and IgG2 additionally in 4 of these cases. In 5 severe cases of hemolytic disease of the newborn (HDN) due to anti-D, large amounts of IgG1 were found, and in 3 of these 5, IgG3 in combination with IgG1. In 8 mild or moderate HDN cases (4 anti-D, 2 anti-E, 1 anti-Fya, 1 anti-Jka), phototherapy sufficed, and IgG1 was the only antibody. In 7 adult patients with malignant lymphoma and a positive DAT (GCT), only small amounts of IgG1 red cell autoantibodies could be demonstrated by flow cytometry. In 5 further patients with malignant lymphoma, a positive DAT, and severe hemolytic anemia, large amounts of IgG1 autoantibodies were found and IgG3 was also present in 3 of these cases. Flow-cytometric determination of IgG subclasses may be a useful tool in immunohematology, since subclass determinations were possible in all of these cases. This method is suited for clinical routine and offers the possibility of sufficient standardization.

Adult↗
PubMed1995

Standardization of the flow cytometric determination of HLA class I antigens, 'platelet-specific' glycoproteins and activation markers.

Flow cytometry (FC) provides a reproducible investigation of cell surface antigens on platelets. The aim of this study was to elaborate appropriate protocols and to compare them with other techniques that have already been published. (1) Venipuncture with tubes containing citrate was better for the preservation of the antigenicity than using ACD tubes. The isolated platelets could not be completely distinguished from detritus and protein aggregates. Therefore a platelet concentration between 10(7) and 10(8)/ml measurement buffer was necessary to obtain a sufficient resolution by FC. (2) Isolation methods using either differential centrifugation or diluted Ficoll-Hypaque as a flotation medium provided platelets of equal purity. The method with Ficoll-Hypaque resulted in a higher number of isolated platelets than differential centrifugation. The demonstration of platelets and their antigens in whole blood without isolation gave good results provided the platelets were not activated. Activation of platelets with 1 NIH-U thrombin/l resulted in the loss of a part of the highly activated platelets because of their aggregation. (3) Comparing different concentrations of paraformaldehyde in PBS, fixation with 1% for 15 min provided the best antigen preservation for most of the antigens investigated. Isolation induced platelet activation. In order to avoid this effect, the whole anticoagulated blood was fixed with 1% paraformaldehyde for 15 min immediately after venipuncture. Then the platelets were isolated using diluted Ficoll-Hypaque. In this way, systemic activation of platelets can be detected with antibodies against glycoproteins which are translocated from the alpha-granules or lysosomes to the cell membrane. These activation markers can be determined on immediately fixed platelets (already in the whole blood) without any interference due to unspecific activation caused by the isolation procedure. (4) Platelet treatment with citric acid at pH 3, in order to remove the antigenicity of HLA-class I molecules, was sensitive to immediate fixation with paraformaldehyde in the whole blood. Fixation after isolating the platelets made it possible to demonstrate antigen stripping, and the free heavy chain, devoid of the beta 2-microglobulin, could be clearly demonstrated. (5) Using standardization beads, the average number of antigenic sites per platelet could be determined for the investigated specificities. It was shown that antibodies which have been directly conjugated or biotinylated and combined with streptavidin-phycoerythrin yielded similar results in terms of the number of antigenic binding sites while unconjugated antibodies in combination with FITC-conjugated anti-mouse-IgG led to overestimation of antigenic binding sites.

Adult↗