172-P

Abstract

Aim To present and discuss the presence of post transplant (tx) donor specific antibody (DSA) and compare methods for detection of this antibody (Ab). Methods Donor and recipient class I (A,B,C) and II (DR,DQ) were typed by SSP. Ab screening was performed using FlowPRA ® Screening beads and Ab identification was performed using LabScreen ® Single Antigen Beads. The C1qScreen™ assay was used to assess for complement fixing antibodies. Typing and Ab reagents were from One Lambda Inc. T and B cell CDC NIH extended crossmatch (XM) was performed pre-tx. Post tx T and B cell flow crossmatch (FCXM) was performed using standard local protocol including pronase treatment. Results The patient received a deceased donor kidney tx in 1994; there were 5 mismatched antigens (A2,B35,Cw4,DR1, and DQ5). Pre-tx CDC XM was T and B cell negative (neg). Recipient was screened for HLA Ab in 2005. Renal function was stable. FlowPRA results were 0% (I) and 76% (II). DSA to DQ5 was detected. Due to stable function, patient was monitored with no treatment. DSA remained present and creatinine levels began to increase in 2008. The B cell FCXM result was positive with sera from 2008 and 2010. The patient was treated with rituximab and high dose IVIg in January, 2011. The B cell FCXM became neg although creatinine remained high initially. Creatinine levels began to drop and returned to baseline by January 2012. The B cell FCXM result remained neg but high MFI DQ5 DSA were still detected. Results from the C1q assay showed complement fixing DSA in the 2008 serum but there were no C1q reactive Ab in the serum from 1 year post treatment thus no complement fixing DSA. Conclusions DSA was detectable 3 years before clinical evidence of graft dysfunction. The C1q assay results appear to correlate better with the FCXM results. The predictive value of a high MFI DSA does not appear to be consistent with the FCXM result. In this case, the FCXM result appears to be a better assessment of the impact of therapy than the MFI value of DSA (DQ5).