Determination of anti‐ADAMTS‐13 autoantibody titers in ELISA: Influence of ADAMTS‐13 presentation and autoantibody detection

Abstract

BackgroundImmune‐mediated thrombotic thrombocytopenic purpura (iTTP) is caused by inhibitory and/or clearing anti‐ADAMTS‐13 (A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats, member 13) autoantibodies. To determine the presence and total level of anti‐ADAMTS‐13 autoantibodies, commercial and in‐house developed ELISAs are performed. However, different ELISA methods vary in relation to the presentation of recombinant (r)ADAMTS‐13 and the detection method of the anti‐ADAMTS‐13 autoantibodies. Currently, the influence of those different approaches on anti‐ADAMTS‐13 autoantibody titers is not known. ObjectivesTo assess the influence of different ADAMTS‐13 presentation‐ and autoantibody detection methods on anti‐ADAMTS‐13 autoantibody titers in ELISA. Materials/MethodsAnti‐ADAMTS‐13 autoantibody titers from 18 iTTP patients were determined using four different set‐ups of anti‐ADAMTS‐13 autoantibody ELISAs. The ELISAs varied in the used presentation of rADAMTS‐13 (directly coated full‐length rADAMTS‐13, directly coated rMDTCS and rT2C2, or antibody‐captured full‐length rADAMTS‐13) and the detection antibodies (polyclonal anti‐human IgG or monoclonal anti‐human IgG1‐4 antibodies). ResultsStrong correlations between the different anti‐ADAMTS‐13 autoantibody ELISA approaches were observed, when using polyclonal anti‐human IgG detection antibodies recognizing all IgG subclasses similarly, independent of the method of rADAMTS‐13 presentation. Anti‐ADAMTS‐13 autoantibody titers correlated less when using a mixture of monoclonal anti‐human IgG1–4, because not all IgG subclasses were recognized with similar affinities. ConclusionAnti‐ADAMTS‐13 autoantibody levels using different methods of rADAMTS‐13 presentation strongly correlate. However, the levels of anti‐ADAMTS‐13 autoantibodies are highly dependent on the detection antibody used, which should detect all IgG subclasses (IgG1–4) equally well.