P062 Characteristics of pre-formed donor specific anti-HLA antibodies associated with their clearance or persistance

Aim Pre-formed non-cytotoxic donor specific anti-HLA antibodies (DSA) are not a contraindication for kidney transplantation. Such DSA are often cleared post-transplant, having minimal effect on graft function. However, pre-formed DSA can also persist post-transplant, potentially increasing the risk of antibody mediated injury. The aim of this study was to evaluate the characteristics of pre-formed donor specific HLA antibodies (DSA) in relation to their clearance or persistence after transplantation in a large population of kidney allograft recipients. Methods Our study population included 681 patients transplanted at our center from Jan 1st 2009 to Dec 31st 2014. Typing of HLA-A, B, C, DR and DQB genes was performed by DNA methods. Serum anti-HLA antibodies were tested at defined intervals pre- and post-transplantation using Single Antigen Beads (One Lambda/ThermoFisher). Unacceptable HLA antigens were reported to UNET using MFI cutoff values of 5000 (HLA-A, B and DR) and 10,000 (C and DQ). Prospective crossmatches were performed in all cases. Patients were transplanted based on a negative flow cytometry and/or CDC crossmatch. Results Out of 681 recipients, 108 (16%) had pre-formed DSA. At one year post-transplant, DSA were cleared in 67 patients and persisted in 41 patients. Patient age, gender and race, transplant type (live or deceased donor) and the number of DSA per patient did not significantly differ in patients who cleared versus patients with persistent DSA. However, patients with persistent DSA were more likely to have DSA directed to the donor HLA-DQB rather than HLA-A, B, C or DR antigens ( p  = 0.041; Fig. 1), DSA with higher MFI ( p p Download high-res image (77KB) Download full-size image Conclusions This study identifies the characteristics of preformed DSA that render them more likely to persist post-transplantation in our patient population. These findings may improve risk stratification of kidney transplant candidates with preformed DSA.