The human platelet alloantigens Br(a) and Brb are associated with a single amino acid polymorphism on glycoprotein Ia (integrin subunit alpha 2).

The human GPIa/IIa complex, also known as integrin alpha 2 beta 1, serves as a major receptor for collagen in platelets and other cell types. In addition to its role in platelet adhesion to extracellular matrix, GPIa/IIa is also known to bear the clinically important Br(a) and Brb alloantigenic determinants, which can result in antibody-mediated platelet destruction. Immunochemical studies showed that the Br antigenic epitopes reside solely on the GP Ia subunit and do not depend on sialic acid residues.

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.

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 deletion in the second exon of an HLA-DRB1 allele found in a DR2-negative narcolepsy patient.

In this report, we describe a new allele of the HLA-DRB 1 gene carrying a form of mutation that has not been observed before. It appeared in an HLA-DR2-negative narcolepsy patient who, besides HLA-DR4, revealed a serologic HLA-DR blank segregating with HLA-DQ1. Oligotyping showed that the new allele belongs to the HLA-DR8 group.

Expression and function of VLA-alpha 2, -alpha 3, -alpha 5 and -alpha 6-integrin receptors in pancreatic carcinoma.

The expression of the VLA-integrins alpha 2, alpha 3, alpha 5 and alpha 6 was studied immunohistochemically in tissue samples from ductal pancreatic cancer, chronic pancreatitis, normal pancreas and in 8 cell lines of ductal human pancreatic cancer. Furthermore, adhesion assays on purified extracellular matrix (ECM)-compounds were used to define the function of alpha 2, alpha 3, alpha 5 and alpha 6 in pancreatic cancer cells. Immunohistochemically, VLA alpha 2 and VLA alpha 6 were moderately to strongly expressed on the basal surface of ductal and acinar cells in normal pancreatic tissue, while centro-acinar cells predominantly expressed VLA alpha 3 and VLA alpha 5.

Decrease of malaria morbidity with community participation in central Java.

Malaria is still a problem in Java-Bali, although the Malaria Eradication Program started in the 1950's. In the First National Five Year Development Plan it was changed to the Malaria Control Program with the aim to reduce the morbidity and mortality rates through surveillance and spraying interventions using the primary health care approach. In 1984 in Central Java there were malaria areas with an average annual parasite incidence (API) between 1 and 7.

Quantitation of soluble HLA class I antigen in human albumin and immunoglobulin preparations for intravenous use by solid-phase immunoassay.

Soluble HLA class I antigens in human plasma preparations possibly play a role in HLA sensitization and modulation of the immune response. We therefore have determined their concentration in albumin and immunoglobulin preparations from several commercial sources and compared these values to the concentration in normal human sera. For this purpose we used a newly developed solid-phase enzyme immunoassay employing rabbit anti-mouse antibody, monomorphic HLA class I monoclonal antibody and a polyclonal enzyme-linked beta 2-microglobulin-specific antiserum.

Autoantibodies against platelet glycoprotein Ib/IX: a frequent finding in autoimmune thrombocytopenic purpura.

Many autoantibodies involved in the pathogenesis of autoimmune thrombocytopenic purpura (AITP) are directed against epitopes on platelet glycoproteins (GP). These autoantibodies are a specific diagnostic characteristic of patients with AITP. In this study, the relative frequency of antibodies against GPs IIb/IIIa and Ib/IX was assessed in sera from 81 AITP patients with a glycoprotein-specific enzyme immunoassay (MAIPA assay) using monoclonal antibodies against these platelet GPs.

Antigenic determinants responsible for the reactions of drug-dependent antibodies with blood cells.

In an attempt to determine the antigenic combining sites of drug-dependent antibodies in patients with drug-related immune haemolysis, we have assessed the reactivity of 35 nomifensine-induced antibodies against human red blood cells (RBC) in the presence of 11 closely related compounds: nomifensine, its three main metabolites including their methoxylated analogues and diclofensine with its three main metabolites. Three types of antibody reactivity patterns could be differentiated: Firstly, antibodies most strongly reactive with nomifensine (n = 12); secondly, antibodies primarily directed against one of its main metabolites (n = 7), and thirdly, antibodies optimally reactive with its unknown metabolites (n = 16). The antibodies preferentially directed against nomifensine showed varying cross reactions with nomifensine-related compounds and in almost all cases also with diclofensine and/or its metabolites.

Blood group A and B determinants are expressed on platelet glycoproteins IIa, IIIa, and Ib.

We report the localization of A, B blood group determinants on intrinsic glycoproteins using anti-A, B IgG antibodies. By radioimmunoprecipitation, anti-A and anti-B precipitated three bands with apparent molecular masses in sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of 159, approximately 120 and 85 kDa under non-reduced conditions and 145, approximately 126 and 97 kDa under reduced conditions. In two-dimensional gel electrophoresis (isoelectric focussing/SDS-PAGE) these three bands could be resolved into six spots and fulfilled previously defined criteria for platelet membrane glycoprotein complexes I a/IIa, Ic/IIa, I b/IX and II b/IIIa.

Sra, a private platelet antigen on glycoprotein IIIa associated with neonatal alloimmune thrombocytopenia.

A new platelet alloantigen, Sra, is described that was defined by an alloantibody detected in the serum of a healthy mother who delivered a child with typical clinical signs of neonatal alloimmune thrombocytopenia (NAIT). The antibody reacted strongly with the child's and father's platelets, but not with platelets of the mother or with those of a highly selected panel representing all known platelet alloantigens. Platelets from 300 unselected normal blood donors also tested negative, suggesting a phenotype frequency in the German population of less than 0.

[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).

[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.

[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.

[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.

[Comparison of 4 crossmatching methods for predicting the success of platelet transfusion].

Long term platelet transfusion support often results in alloimmunization of the recipients and refractoriness to further platelet transfusions. Crossmatch tests between the recipients' serum and the donor platelets offer a potential solution to this problem. In the present study, 207 donor-recipient pairs were studied in 65 patients.

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.

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.

Immunochemical characterization of the new platelet alloantigen system Bra/Brb.

We report the immunochemical characterization of the new platelet-specific alloantigens Bra and Brb. Bra antibodies were from mothers of children with neonatal alloimmune thrombocytopenia (NAIT), and anti-Brb was found in the serum of a polytransfused patient. By radioimmunoprecipitation, anti-Bra and anti-Brb precipitated two proteins with apparent relative molecular masses in sodium dodecyl sulphate-polyacrylamide gel electrophoresis of 155,000 and 130,000 under non-reduced conditions, and of 165,000 and 148,000 under reduced conditions.

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.

The Bra/Brb alloantigen system on human platelets.

Anti-Bra was first identified in four cases of neonatal alloimmune thrombocytopenia (NAIT). The antigen Bra is localized on the glycoprotein Ia/IIa complex of platelets. Anti-Bra can best be detected by a glycoprotein-specific immunoassay using monoclonal antibodies for antigen immobilization (MAIPA assay) and radioimmunoprecipitation (RIP).

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).