P046 Under assessment of DSA strength in single antibody bead assays may lead to poor outcome in kidney transplantation

• Published in: Human immunology Vol. 79; p. 93
• Main Authors: Das, Ballabh, Norin, Allen J., Sumrani, Nabil, Tedla, Fasika, John, Devon
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-10-2018
• ISSN: 0198-8859; 1879-1166
• DOI: 10.1016/j.humimm.2018.07.104

Solid phase anti-HLA antibody tests have become an important tool in predicting the compatibility of donor-recipient pairs for kidney transplantation. Additionally, single antigen bead (SAB) assays provide valuable information for the management of post-transplant immunotherapy. However, there can be limitations to SAB assays, for example, the presence of donor specific IgM antibodies and/or binding of high levels of compliment may block binding of donor specific IgG antibodies (DSA) to the SAB. This could possibly result in an under estimation of DSA. The following case is an example of this phenomenon. A 48 years old female patient (HLA Type: A1 A29 B53 B72 DR8 DR13) was transplanted with a deceased donor kidney (HLA Type: A2 A33 B53 B58 DR8 DR11 DQB7 DQA04 DQA05 DPB01:01 DPB04:02) in 2017. The patient was presensitized (pregnancy) to a donor antigen A2 (MFI of 4 A2 beads  = 3904) with an associated epitope 144TKH (MFI = 5101, includes A68, A69). On day 3 post-transplant, there was no detectable antibodies to donor antigens due to the sponge effect of the transplanted kidney. On day 6 antibodies to A2 (MFI = 5000) and the associated epitope 144TKH (MFI = 8946) reappeared. Additionally, a low level of de novo antibodies to B*58:01 (MFI = 716) and DPB1*04:02 (MFI = 864) was detected. On day 12, antibodies were detected to only A*02:01 (MFI = 615), while a significant increase in B58 antibody was observed (MFI = 9025). At this time, a biopsy indicated antibody mediated graft rejection; creatinine was 10 mg/dl. Accordingly, the patient’s antibody was further evaluated by an AMOS one wash CDC cross match with frozen cells and sera from day 6 and 12. On day 6, CDC-XM was negative, but on day 12 the CDCXM was positive. The level of DSA to class I of MFI 9640 would typically not give a positive CDC cross match. To determine if there was interference of IgM and/or compliment, the 12-day serum was treated at 63C for 13 min to inactivate these molecules. The heat-treated serum demonstrated an MFI to A*02:01 of MFI = 20,567 compared to an MFI of 615 before heat inactivation. Unfortunately, treatment for antibody-mediated rejection was not initiated soon enough to save the kidney. Although it is rare to observe IgM and/or compliment interference with SAB assays (4 out of 3020 cases, 0.1%), post-transplant assessment of DSA should be performed with heat inactivated sera or other methods to eliminate the under estimation of the strength of IgG antibodies.
A.J. Norin:2. Consultant; Company/Organization; ICON PLC, Stony Brook Pathologist. 3. Speaker’s Bureau; Company/Organization; immucor, one lambda.