Tissue Antigens ISSN 0001-2815
LETTER TO THE EDITOR
Endogenous anti-C1q antibodies do not interfere with the C1qScreen™ assay D. Focosi1 , M. De Donno2 & F. Pratesi3 1 Department of Translational Research, University of Pisa, Pisa, Italy 2 Laboratory of Immunogenetics, Careggi Hospital, Florence, Italy 3 Laboratory of Immunoallergology, Pisa University Hospital, Pisa, Italy Key words: anti-C1q; C1qScreen; complement
Dear Editor, For decades, the complement cascade has played a central role in antibody identification and compatibility [complementdependent cytotoxicity (CDC) crossmatches] and for the diagnosis of antibody-mediated rejection (C4d staining on histology and erythrocyte-bound C4d), and has inspirited new anti-rejection drugs (eculizumab and rC1INH). Interference by complement components is already wellknown in the setting of conventional (IgG) Luminex™ assay, where C1r2 -C1s2 tetramer blocks the part of the Fcγ region that the anti-IgG secondary antibody binds to, causing the prozone phenomenon (1); to date, an array of effective solutions has been developed (2). The recently FDA- and CE-approved C1qScreen™ assay is gaining importance in the transplantation field, being able to discriminate dangerous from harmless donor-specific antiHLA antibodies after transplantation (3). Briefly, the assays use heat-inactivated (hence complement-depleted) patient serum reconstituted with a standard dose of recombinant human C1q. C1q binds to the Fc tails of paired IgG1/3 or IgM molecules bound on Luminex™ beads, and C1q-fixing antibodies are revealed by adding a R-phycoerythrin-labeled secondary antibody against human C1q. As all samples negative in C1qScreen™ had an antibody titre
LETTER TO THE EDITOR
Endogenous anti-C1q antibodies do not interfere with the C1qScreen™ assay D. Focosi1 , M. De Donno2 & F. Pratesi3 1 Department of Translational Research, University of Pisa, Pisa, Italy 2 Laboratory of Immunogenetics, Careggi Hospital, Florence, Italy 3 Laboratory of Immunoallergology, Pisa University Hospital, Pisa, Italy Key words: anti-C1q; C1qScreen; complement
Dear Editor, For decades, the complement cascade has played a central role in antibody identification and compatibility [complementdependent cytotoxicity (CDC) crossmatches] and for the diagnosis of antibody-mediated rejection (C4d staining on histology and erythrocyte-bound C4d), and has inspirited new anti-rejection drugs (eculizumab and rC1INH). Interference by complement components is already wellknown in the setting of conventional (IgG) Luminex™ assay, where C1r2 -C1s2 tetramer blocks the part of the Fcγ region that the anti-IgG secondary antibody binds to, causing the prozone phenomenon (1); to date, an array of effective solutions has been developed (2). The recently FDA- and CE-approved C1qScreen™ assay is gaining importance in the transplantation field, being able to discriminate dangerous from harmless donor-specific antiHLA antibodies after transplantation (3). Briefly, the assays use heat-inactivated (hence complement-depleted) patient serum reconstituted with a standard dose of recombinant human C1q. C1q binds to the Fc tails of paired IgG1/3 or IgM molecules bound on Luminex™ beads, and C1q-fixing antibodies are revealed by adding a R-phycoerythrin-labeled secondary antibody against human C1q. As all samples negative in C1qScreen™ had an antibody titre
