26-P : PERSISTENT C1q BINDING DSA PATTERNS ASSOCIATED WITH INCREASED LONG-TERM POSTTRANSPLANT AMR, CMR, AND CAV IN HEART TRANSPLANT RECIPIENTS

Aim Posttransplant (postTX) determination of de novo donor antigen specific antibody (DSA) has been monitored traditionally by conventional Luminex single antigen bead assays (LSAB-IgG). Correlation of DSA detected by the LSAB C1q binding assay and clinical outcomes remains to be investigated in our heart recipient population. Methods Sera from 48 recipients transplanted between Jan 1994 and Oct 2012 were included in this study. All recipients were transplanted with a negative CDC xm with 3 having weak flow cytometric xms. Multiple postTX sera were tested by LSAB-IgG and for C1q binding and were shown to have DSAs. The postTX sera were received at routine clinic visits and at the time of biopsy. Biopsies were graded based on the new ISHLT grading scale. Results Two major patterns of DSA binding were observed:. 1) Persistent C1q binding DSA patterns, none of which reverted to C1q negative binding patterns (N=29) and 2). Persistent C1q negative binding patterns (N=19)(Table 1). The antibody patterns were shown to be persistent an average of 18 mo. (range 1 and 54 mo.). The predominant DSA specificity was class II: DQ alone (N=32), DRB3/4/5 (N=4), DQ+ DRB3 or 4 (N=6), DRB1 (N=1). Conclusions Patients with the persistent C1q binding DSA had a higher incidence of AMR, CMR, NF-MACE, and a significantly higher incidence of CAV. Predominant class II, specifically anti-HLA DQ DSA patterns, were observed. No C1q positive pattern resolved to negative. Thus, some antibody patterns may be easier to resolve after therapy for rejection. Not all patients with the C1q binding DQ DSA profile have experienced a clinical event to date suggesting antibodies to non-HLA or a possible subclinical event.[figure1]