P045 Kidney transplant with historic but no current DSA – A case study

Presence of donor-specific HLA antibodies (DSA) at the time of transplant is associated with poor outcome. DSA may be present in historic serum samples but not at the time of a kidney offer. Going forward with the transplant holds the risk of a memory B-cell response upon re-exposure to a specific HLA antigen or epitope. A patient with X-linked Alport syndrome was investigated for a kidney transplant. Anti-HLA class II antibodies were observed following pregnancy, which were specific to her husband’s mismatched DR and DQ antigens. A year later, she received a blood transfusion and had an episode of aseptic peritonitis while on dialysis. Class I HLA antibodies appeared but were observed over a period of 7 months. Thereafter, anti-HLA antibody screening using FlowPRA beads and identification using Luminex single antigen beads showed disappearance of class I antibodies but persistence of a single anti-HLA-DR antibody developed after prior pregnancy. Three years later, a kidney from a DCD donor was offered and transplanted despite presence of historic DSA against 2 HLA-B antigens. A CDC crossmatch proved negative using a current serum whereas a flow cytometric crossmatch using 3 DSA-containing historic sera gave positive but inconsistent results (T + B+, T-B+, T-B-). One week after transplant, historic DSA reappeared (3000 MFIs). Despite absence of biopsy-proven rejection, short-term treatment comprising plasmapheresis, rituximab and low-dose IVIg was initiated. DSA quickly disappeared from circulation with only an HLA-DR-specific reactivity from the previous pregnancy. Without any further desensitization treatment, the patient has not demonstrated re-appearance of DSA nor experienced antibody-mediated rejection (AMR) as demonstrated upon for-cause and protocol biopsies, up to 8 months posttransplant at the time of abstract submission. This case demonstrates that, although DSA may reappear following re-exposure to a sensitizing HLA antigen/epitope, acceptable transplant outcome can be achieved without AMR. Time between DSA development and transplant could be a factor in identifying acceptable HLA mismatches.