Abstract 16877: Correlation of Antibody Binding Strength to Complement Fixation

Abstract

Background: In patients (pts) who are highly sensitized, desensitization therapy is commonly applied to reduce antibody (Abs) load and to reduce potential morbidity and mortality following heart transplant (HTx). It is not known as to what level of antibody binding is needed to initiate desensitization therapy. It is believed that high binding Abs may have the ability to fix complement and lead to cytotoxicity. Methods: Between 2011 and 2012 we assessed 13 highly sensitized pts who were noted to have standardized fluorescence intensity (SFI) >100,000 pretransplant. A complement binding assay (C1q binding assay) was then applied to these Abs to assess for a correlation of binding to cytotoxicity. Correlation statistics were used to derive significance between higher antibody binding and capacity to bind complement. Results: There seems to be no correlation between the different binding strength and C1q positivity. However, when evaluating Luminex 1:8 test, there seems to be correlation between class I binding strength with C1q positivity. There was C1q positive rate of 10.8% in SFI 200,000 range. Conclusions: Undiluted antibodies do not correlate to C1q binding ability. However the 1:8 dilution test seems to provide an better prediction of complement binding. 1:8 dilutions should be performed to accurately assess the ability for antibodies to bind complement.