Marta Crespo, Alberto Torio, Virginia Mas, Dolores Redondo, Maria J.Pérez-Sáez, Marisa Mir, Anna Faura, Rita Guerra, Olga Montes-Ares, Maria D.Checa, Julio Pascual
Anti-HLA donor-specific antibodies (DSA) identified by single antigen bead array (SAB) are questioned for their excess in sensitivity and lack of event prediction after transplantation. Population and methods: We retrospectively evaluated specific types of preformed DSA (class I, class II or C1qfixing) and their impact on graft survival. Kidney transplantations performed across negative CDC-crossmatch were included (n = 355). Anti-HLA antibodieswere tested using SAB to identify DSA and their capacity to fix C1q.
Results: Twenty-eight patients with pretransplant DSA+ with MFI N 2000 were selected to assess C1q fixation. DSA were C1q+in 15 patients and C1q- in 13, without significant differences in demographics, acute rejection, graft loss or renal function. The maximum MFI of DSA in patients with C1q-fixing DSA was significantly higher (p = 0.008). Patients with DSA class-I suffered more antibody-mediated rejection (AMR) and had worse graft survival than class-II. The capacity of DSA I to fix C1q did not correlate with rejection, graft function or graft loss.
Conclusions: C1q testing in pretransplant serawith DSA was unable to predict acute antibody-mediated rejection or early graft loss, but the presence of DSA class I compared to DSA only class II did. Despite non-fixing complement in vitro, pretransplant C1q-negative DSA I can mediate rejection and graft loss.
Keywords: Antibody-mediated rejection, Complement, Donor-specific antibody, HLA antibody, Kidney transplantation
Ge Chen and Dolly B. Tyan
Solid phase Luminex® and flow cytometric single antigen bead assays offer exquisite sensitivity and specifi city for HLA antibody detection. Unlike the historical complement-dependent cytotoxicity (CDC) method, these assays do not distinguish complement fixing from non-complement fixing antibody, the former of which are considered the most clinically relevant in the peri-transplant period. This chapter describes a novel solid phase C1q binding assay to distinguish HLA antibodies that can bind the first component of complement (C1q). These antibodies have the capacity to initiate the complement cascade irrespective of whether that actually occurs. The C1q assay detects many more complement fixing antibodies than are observed by the less sensitive and less specific CDC assay.
Keywords: HLA antibody, Solid phase assay, Single antigen beads, Luminex®, Transplantation, Complement, C1q
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