AMR is a significant contributor of graft loss. Detection of DSA and C4D in Peri Tubular Capillaries (C4d+) has improved our understanding of AMR. It is unclear if a correlation exists between the titer/ number of DSA to C4d + or outcomes. AIM: The purpose of our study was two fold. First, to identify if titer or number of DSA correlated to C4d+. Second, to identify any clinical significance between the number of DSA detected and clinical outcomes. METHODS; Data of all biopsies performed in the past 5 years was collected. For all biopsies reported as C4d+, the results of HLA Ab testing (Luminex) at the time of the biopsy was collected. All DSA with Mean Fluorescent Intensity (MFI) >1000 were considered significant (SDSA) and noted while titers below 1000 were not considered significant (NSDSA). C4d+ biopsy data was collected not only for the Peritubular capillaries but for Glom and tubular basement membrane (C4d+TBM) as well. Results were grouped by the number of SDSA into <2SDSA or >2SDSA. Clinical outcomes were measured as functional staus of allograft and serum Creatinine.37 biopsies were reported as C4d+ and concurrent DSA samples were not available for 6 Bx. Bx were from 17 Women and 14 Men. RESULTS: The mean number of DSA detected was 2.5 (range 0-11) but 16/31 were noted to have less than 2 SDSA (8 pts had 1, 2 pts had 2 and 6pts had no SDSA). 25/31 had at least 1 SDSA suggesting a MFI of 1000 appears to be a good marker of predicting C4d. However, there appears to be no correlation to the number of SDSA and clinical outcome as the rate of graft loss was no different between the group of <2SDSA or >2SDSA. One poor prognostic indicator appeared to be the the presence of C4d+TBM in addition to C4d+. Interestingly, almost all of these biopsies had the presence of DQ AB detected in the serum. CONCLUSIONS: Our study has several clinical implications. First, a MFI >1000 appears to correlate well to C4d+ and this data can be used when loading Unacceptable antigens in the UNOS database. Second, presence of multiple SDSA does not seem to connote any higher risk of graft dysfunction when compared to presence of fewer SDSA. Finally, C4dTBM and C4d+ together appears to have a more deleterious impact on graft function and that the presence of DQ antibodies appears to have some correlation to C4dTBM. Prospective data is being collected to analyze the impact of DQ SDSA on C4d+ and C4d+TBM cohort of AMR.

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