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Background and Objectives HPA-1a antibodies account for 70-80% of cases of fetal-neonatal alloimmune thrombocytopenia ( FNAIT) in Caucasians. However, numerous workshops have demonstrated variability in their detection. We recently showed that exposure of α IIbβ3 to ethylene diamine tetraacetic acid ( EDTA) affected binding of many anti-α IIbβ3 monoclonal, and HPA-1a allo-, antibodies; this adversely affected sensitivity of the monoclonal antibody-specific immobilization of platelet antigens ( MAIPA) assay and indirect platelet immunofluorescence test ( PIFT). This study presents results from an international workshop studying the impact of cation chelation on HPA-1a antibody detection in routine diagnostic laboratories. Materials and Methods Serum and EDTA-anticoagulated plasma samples containing anti- HPA-1a were distributed to 39 laboratories. Participants were asked to detect and identify any HPA antibodies present. Results 2/39 (5·1%) participants were able to detect and identify anti- HPA-1a in the serum, but not in the plasma sample. EDTA plasma reduced MAIPA assay sensitivity by ≥20% in 17/24 (70·8%) laboratories and by ≥50% in 9/24 (37·5%) when using HPA-1a1a platelets (mean: 27·7%, range 0-85·1%); when using HPA-1a1b platelets 3/4 (75%), participants reported ≥50% loss of sensitivity (mean 65·6%, range 0-96·6%). A small but significant increase in optical densities was observed in antigen capture ELISA assays when using plasma (mean difference: 0·081, P < 0·01). Insufficient PIFT data were returned to draw firm conclusions. Conclusion Use of EDTA plasma significantly affects the sensitivity of the MAIPA assay and can affect detection of even potent, FNAIT-causing examples of anti- HPA-1a. These data highlight the importance of use of α IIbβ3 in an appropriate conformation for the sensitive detection of anti- HPA-1a. [ABSTRACT FROM AUTHOR]

Background and Objectives Fetomaternal alloimmune thrombocytopenia (FMAIT) is caused by maternal antibodies against a human platelet antigen (HPA) present on fetal, but absent from maternal platelets. We identified and characterized a case of FMAIT due to anti-HPA-1a in a mother with an HPA-1a1b genotype. Materials and Methods The first child of a 29-year-old mother presented with a petechial rash and a platelet count of 8 × 109 per l. Upon routine serological investigation, a discrepancy between the HPA-1a genotype and phenotype prompted the sequencing of the 15 exons of the ITGB3 (integrin β3, GPIIIa and CD61) gene in the mother. Results The mother was genotypically HPA-1a1b heterozygous but phenotyped as HPA-1a negative. Sequencing of the ITGB3 exons confirmed HPA-1a1b heterozygosity, but also identified a novel single nucleotide insertion in exon 10 leading to a frameshift and premature termination at amino acid 471 of ITGB3. Maternal anti-HPA-1a was detected but with a pattern typical for a low-affinity antibody. Three transfusions of HPA-1a and -5b negative neonatal platelet concentrates were required to return to a safe platelet count. Conclusion A rare ITGB3 allele was uncovered by the investigation of a severe case of alloimmune thrombocytopenia in a mother with HPA-1a antibodies who genotyped as HPA-1a1b. [ABSTRACT FROM AUTHOR]

The article discusses the impact of monoclonal antibody therapies in transfusion medicine, in Great Britain. Monoclonal antibodies bear a great impact on the safety of the transfusion of blood. Blood donors can already be typed for the majority of relevant blood groups. This can be achieved through monoclonal antibodies of murine or of human blood rather than polyclonal antibodies.

The article discusses the relationship between the nature of the blood group and the type of antibody response in the adaptive immunity and blood transfusion. It states that the T cells, B cells, and antigen-presenting cells (APCs) are the key players for the formation of antibodies. It adds that after migrating the progenitor cells from the circulation into the epithelial thymus, T and B cells with their T-cell receptor (TCR) and B-cell receptor (BCR) may respond to antigens.

Presents three linked nomenclature tables to support the systematic use of the human platelet antigens (HPA) nomenclature. Use of international databases containing information on the sequence of the human genome; Description of a formal process by which HPA designations should be assigned under the control of the Platelet Nomenclature Committee (PNC); Categorization of platelet-specific protein alloantigens; Responsibilities of the PNC.

This is the first study describing recombinant human antibody fragments directed to the autoantigen proteinase 3 (PR3) From an immune B cell source. Detection of these autoantibodies has proven valid for the diagnosis and monitoring of Wegener's granulomatosis, The described antibody fragment (scFv) was isolated front a phage display library prepared from the IgG-positive splenic lymphocytes of a patient with systemic autoimmunity. The cloning strategy was designed to maintain the diversity of the antibody variable gene repertoire. and sequencing of several variable genes demonstrated that all major heavy and light chain families were represented. We found an over-representation of particular heavy chain variable domains in splenic lymphocytes which differ from the ones frequently found in peripheral blood lymphocytes. It was possible to obtain specific' scFv to PR3 after a single round of selection and the binding could be inhibited by the patients' sera. Although the antibody fragments in the picnic repertoire were found to he highly mutated. it was interesting to find that the selected scFv showed only limited somatic mutation. Furthermore, we could demonstrate that the removal of the mutations had no died on binding specificity. [ABSTRACT FROM AUTHOR]

Recently it has been demonstrated that human antibody fragments with binding activities against self antigens can be isolated from repertoires of rearranged V genes from non-immunized humans. We have applied phage display technology to study the B cell repertoire for antibody activity against neutrophil cytoplasmic antigens. These antibodies may play an important role in Wegener's granulomatosis (WG) and related forms of vasculitides. Autoantibodies in patients with WG are directed against proteinase 3. The immunodominant antigen in other forms of vasculitis is myeloperoxidase, but the B cell response can also be directed against other neutrophil enzymes, e.g. lysozyme, human neutrophil elastase. lactoferrin and cathepsin G. We show here that anti-self reactivity against neutrophil cytoplasmic antigens can be detected in the rearranged V gene repertoire of healthy individuals and that the reactivity can be directed against structural related epitopes which are present on different neutrophil cytoplasmic antigens. The scFv with binding activities were sequenced and the V gene usage, the level of somatic mutations and the immunoserological characteristics of the antibody fragments are discussed. Further evidence is presented that antibody fragments consisting only of a heavy chain variable domain can recognize neutrophil cytoplasmic antigens in a specific manner. These single-domain antibody fragments were used in experiments designed to establish the relative role of the light chain variable domains in antigen binding. [ABSTRACT FROM AUTHOR]

We studied the relationship between reticuloendothelial Fc receptor function and some parameters of the humoral immune response in vivo and in vitro in 18 SLE patients. Fc receptor-mediated immune clearance correlated remarkably well with (a) a decrease of antigen specific IgG after immunization with a primary test antigen (α-Helix pomatia haemocyanin) (P < 0.01) and (b) the spontaneous IgG release in vitro of B cells obtained from peripheral blood (P < 0.01). These two parameters were significantly interrelated. Reticuloendothelial Fc receptor function was not related to serum IgG levels. The study provides evidence for an association between polyclonat B cell activation and Fe receptor-mediated immune clearance in SLE patients. The possible nature of this association is discussed. [ABSTRACT FROM AUTHOR]

Reticuloendothelial system (RES) Fc receptor-mediated immune clearance was measured in 18 patients with systemic lupus erythematosus (SLE). Only two patients, with major disease activity, had a prolonged T½ of the blood disappearance curve of injected IgG coated red cells in comparison to 22 healthy controls. Circulating immune complexes (CIC) were studied with three methods: PEG precipitation, Clq-ELISA and the indirect granulocyte phagocytosis test (IGFT). The T½ of the blood disappearance curve related significantly to the IGFT (r=0.55, P <0.05) and not to the PEG and Clq-ELISA test. Although HLA-DR3 phenotype frequency was significantly increased in our SLE population (P < 0.05), it was not related to Fc receptor function. Similarly, HLA-DR2 phenotype was not related to RES Fc receptor function. These data do not support the concept that a genetic HLA linked defect in reticuloendothelial Fc receptor function is a primary cause of SLE, predisposing the inflicted individual to immune complex deposition. However, Fc receptor-mediated immune clearance seems to be related to disease activity itself and to levels of CIC. [ABSTRACT FROM AUTHOR]