Browsing by Subject "Allograft"

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    General insufficiency of the classical CDC-based crossmatch to detect donor-specific anti-HLA antibodies leading to invalid results under recipients’ medical treatment or underlying diseases
    (F. Hernández y Juan F. Madrid. Universidad de Murcia: Departamento de Biología Celular e Histología, 2012) Schlaf, Gerald; Mauz-Körholz, Christine; Ott, Undine; Leike, Steffen; Altermann, Wolfgang
    Antibodies directed against HLA antigen of a given donor represent the most prominent cause for hiper-acute and acute rejections. In order to select recipients without donor-specific antibodies the complement-dependent cytotoxicity (CDC-) crossmatch as the standard procedure was established. As a functional assay it strongly depends on the availability of isolated donor lymphocytes and in particular on their vitality. However, due to several diseases or pharmacological treatment of a given recipient unexpected “false-positive” results of the CDC- crossmatch may arise. We here present three groups of patients which demonstrate the limits of the conventional crossmatch. 1) Kidney recipients before living donations exhibited positive CDC-reactions due to their conditioning using the therapeutical anti-CD20 mAb Rituximab (n=7), routinely used to deplete B-cells, or the anti-CD25 mAb Basiliximab (n=2) to inhibit the proliferation of activated T-cells. 2) Recipients suffering from various leukaemias (n=5) exhibited “positive” CDC-crossmatches using PBL of the donors, although formerly these patients had never shown anti-HLA antibodies. Instead of donor-specific allo-antibodies, cytostatic agents such as 6-Mercaptopurine led to an unspecific cell death. 3) Patients projected for post mortem or living kidney donations (n=44) exhibited “positive” CDC-crossmatch results which were not in accordance with their former antibody status and, partially, with high degrees of HLA-matching. These implausible results were due to underlying auto-immune false-positive B-cell crossmatches by immune diseases, mainly of the systemic Inmune Complex Type III such a Lupus Erythematosus, mainly leading to false-psitive B- cell crossmatches by complexes binding to Fcγ -receptors. In all these 58 cases the alternatively performed ELISA-based “Antibody Monitoring System” (AMS-) crossmatch assay was not artifically affected, suggesting that this assay may be comprehensively established at least for the cases described.
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    Solid phase-based cross-matching for solid organ transplantation: Currently out-of-stock but urgently required for improved allograft outcome
    (Universidad de Murcia, Departamento de Biologia Celular e Histiologia, 2020) Schlaf, Gerald; Bau, Daniela; Horstmann, Nathalie; Sawers, Gary; Altermann, Wolfgang
    Transplant recipients who have undergone sensitizing events, such as pregnancy, blood transfusion or previous transplants, frequently develop antibodies directed against the highly polymorphous human leukocyte antigen (HLA)-molecules. These pre-formed, donor-specific antibodies (DSA) present a high risk of causing organ failure or even complete loss of the grafted organ as a consequence of antibody-mediated, hyper-acute or acute allograft rejection. In order to detect DSA, the so-called functional complement- dependent lymphocytotoxicity assay (CDC-XM) was established about 50 years ago. Although effective in improving the outcome of solid organ allo-grafting, for the last ten years this assay has been controversially discussed due to its low sensitivity and especially because of its high susceptibility to various artificial factors, which generally do not yield reliable results. As a consequence, novel immunochemical test systems have been developed using ELISA- or bead-based solid phase assays as replacements for the traditional CDC- based assays. Because these assays are independent of single or vital cells, which are frequently not available, they have provided an additional and alternative diagnostic approach compared with the traditional CDC-based and flow-cytometric analyses. Unfortunately, however, the AMS-ELISA (Antibody Monitoring System), which was the first system to become commercially available, was recently discontinued by the manufacturer after seven years of successful use. Alternative procedures, such as the AbCross-ELISA, had to be either considerably modified, or did not yield reliable results, as in the case of the Luminex-based assay termed DSA. We draw the conclusion that due to the unique features and fields of application reviewed here, the implementation of solid phase cross-matching still represents an urgent requirement for any HLA-laboratory’s routine tasks