1007-LB: A New C1q-Flow Crossmatch for Detecting Donor Specific Complement Fixing Antibodies (CFAb)

Abstract Aim It is generally accepted that a positive cytotoxic lymphocyte crossmatch (CDC-XM) is a contraindication for transplantation. However the assay is insensitive for detecting low levels of alloantibodies. The Flow cytometry crossmatch (IgG-FXM) is very sensitive but cannot differentiate HLA complement fixing antibody (CFAb) from non-CFAb and its clinical significance is still controversial. Based on the clinical relevance of CDC, we have successfully developed a new Flow Cytometry C1q crossmatch (C1q-FXM) to specifically detect Methods Donor PBMCs (0.1x 10 6 ) were incubated with 30 ul serum and CD3-PerCPCy5.5, CD19-FITC and SAPE-Bio-C1q for 30 minutes. After washing, the cells were collected and analyzed on a Canto-II flow cytometer. The PE fluorescence intensity on the T and B lymphocytes is proportionate to the amount of C1q fixed on the cell surface and reflects the complement fixing capability of DSA. CFAb with high sensitivity. Results A total of 120 XMs (66 Tc-XM, 54 Bc-XM) were performed in parallel using CDC-XM, IgG-FXM, and C1q-FXM. C1q-FXM correlated well with CDC-XM but has higher sensitivity. The concordance of two crossmatches was 88% (P  Conclusion The newly developed C1q-FXM combines the advantage of the CDC-XM for detecting CFAb with the high sensitivity of the IgG-FXM assay. It can replace the traditional CDC-XM.