Impact of sensitization events on HLA alloimmunization in kidney transplantation candidates

Alloantibodies against human leukocyte antigens (HLA) may develope after exposure to blood transfusions, pregnancy and/or previous transplantation. HLA antibodies represent an important immunological barieer to successful organ transplantation. The aim of our study was to assess the frequency of exposure to different sensitizing events (SEs) and evaluate their effect on HLA alloimmunization in kidney transplantation candidates. We performed retrospective analysis of the HLA antibody screening results in 163 patients on kidney transplant waiting list in Clinical Hospital Center Rijeka tested from March 2012 until the end of December 2015. The screening of HLA antibodies has been performed periodically every three months, four times per year by CDC and Luminex assays. Informations on earlier and recent SEs were obtained from transplantation candidates, their nephrologists and medical records. Of total 163 patients, 114 (69, 94%) were exposed to one or more SEs. The most common SE were blood transfusions. At least one red blood cell unit received 92 patients (56, 44%). Pregnancies reported 57 female (34, 97%) and previously transplanted were 24 recipients (14, 72%). In 105 patients (64, 42%), regardless a history of SEs, HLA antibodies were not detected by CDC nor by Luminex techniques. HLA alloimmunization occured in 48 patients (29, 45%) exposed to SEs and in 10 patients (6, 13%) without history of SEs. In 21 patients (36, 21%) they were detected by CDC and Luminex (CDC+LUM+) while in additional 37 candidates (63, 79%), including all sensitized patients without known SEs, HLA antibodies were detected by Luminex only (CDC-LUM+). Exposure of patients on waiting list to SEs represent a risk factor of developing HLA antibodies. Blood transfusions are the most frequent and the most susceptible to our influence. They should be minimized or avoided in transplantation candidates whenever is possible.