Background: Antibody-Mediated Rejection (AMR) due to HLA donor‐specific antibodies (DSA) is associated with poor outcomes in lung transplant recipients (LTR). Successful AMR treatment using therapeutic plasma exchange (TPE) improves clinical outcomes in LTR. The objective of this study was to assess the clinical utility of 1:16 serum dilution HLA antibody test results as a predictor of response to TPE for AMR treatment in LTR.
Methods: A retrospective analysis of 21 LTR diagnosed with AMR due to de novo HLA DSA (dnDSA) and successfully treated with TPE was performed at Mayo Clinic (n = 7) and Temple University Hospital (n = 14). HLA antibodies were detected by Luminex single antigen beads assay. Mean Fluorescence Intensity (MFI) levels were measured before the 1st and after the 5th TPE session using undiluted and 1:16 diluted sera. Statistical analysis was performed using IBM® SPSS® Statistics (v26; Armonk, NY).
Results: Of 21 patients, 9 and 12 patients were diagnosed with early (< 3 months post-transplant) and late (6 months – 3 years post-transplant) AMR respectively. All patients had Class II dnDSA. In addition, 55% and 16% of LTR with early AMR and late AMR, respectively also had class I dnDSA. The MFI for all positive dnDSA in 1:16 diluted sera collected before 1st TPE demonstrated a significant correlation with MFI in undiluted sera collected 1 day after 5th TPE in both early (Fig. 1A; R2 = 0.8786) and late (Fig. 1B; R2 = 0.9045) AMR post-transplant. In addition, reduction in MFI of dnDSA in 1:16 diluted sera correlated with better overall LTR survival following TPE (Fig, 2; p = 0.01).
Conclusion: The MFI of 1:16 serum dilution before 1st TPE may be utilized as a surrogate to predict response to TPE for AMR treatment and overall survival in LTR.