Aim: UNOS allows the listing of unacceptable antigens for candidate due to the presence of specific anti-HLA antibodies. HLA-DR53 antibody only results in a cPRA of 50% if called “Unacceptable”. We proposed DR53 antibody only may cause some candidates to lose 50% opportunity for organ offers. This study is mainly focused on the reality of HLA DR53 antibody’s activity on live cells and solid phase detection in order to reduce negative impact of organ offers to candidates who only have DR53 antibody positive.
Method: Cases and anti-HLA DR53 detection: 10 Patients’ sera with reported only HLA DR53 antibodies positive by solid phrase assay (Luminex Single Antigen Beads-One Lambda)-OL SAB, and cutoff of positive is 1,000 MFI; these sera’ DR53 antibody were tested by Immucor single antigen beads (SAB) as well, see table. Crossmatch Test: Three color B cell crossmatches were performed by CytoFlex Flow cytometer -Beckman Coulter. The surrogate cells with known DR53 expression were used to crossmatch. The cutoff of B cell crossmatch is 70 Median Channel Shift (MCS).
Results: There were 10 cases with DR53 antibody positive only (mean: 7,608MFI) detected by OL SAB and 7 of 10 were confirmed positive (mean: 4,701MFI) by Immucor SAB. SAB tests indicate that the sensitivity of OL SAB is higher than Immucor SAB but specificity needs to further study. B cell crossmatch results indicate that three out four positive crossmatch sera have DSA-DR53 >11,000 MFI and only one B cell crossmatch positive with DSA-DR53 <3,000MFI. The one B cell crossmatch negative with a higher MFI was at 11,092 MFI. Overall, there are 40% B cell crossmatch positive with DR53 antibody positive and mean MCS of 10 crossmatches is 42. Based on our transplant program criteria for crossmatch acceptance, all of 10 pairs’ crossmatch are considered to be transplantable. So, based on this study, all patient with only DR53 antibody positive could have chance to acceptable the organ offers if DR53 is not listed as unacceptable HLA antigen.
Conclusion: This study suggests that if the patient has DR53 antibody positive without any associated DR antigens, it is better not to list as an unacceptable HLA antigen to give the transplant candidates 50% opportunity of deceased donor offers. However, if the patient has higher MFI of DR53 antibody, a surrogate crossmatch should be considered, before deciding to list as unacceptable.
