Effects of different sensitization events on HLA alloimmunization in solid organ transplantation patients

HLA alloimmunization is caused by various sensitization events, such as transfusion, pregnancy, or organ transplantation. However, the effects of a particular sensitization event on HLA alloimmunization have not been well studied in parallel using an identical test method. We evaluated how different sensitization events affect the panel-reactive antibody (PRA) status in solid organ transplantation candidates.

PRA identification tests were performed on 674 patients (354 males and 320 females) using Luminex assay kits (LIFECODES, Gen-Probe, Stamford, CT, United States). PRA-positive rates (HLA-A, B, or DR antibodies of median fluorescence intensity [MFI] values of ≥1000) and antibody strengths in PRA-positive cases were analyzed according to the different sensitization events and gender.

PRA (class I and/or II)-positive rates were significantly higher in patients with transfusion (33.0%; P = .001), pregnancy (71.4%; P < .001), or transplantation events (76.9%; P < .001) than in controls without any identifiable sensitization events (5.6%). Transplantation had the strongest immunization effect, especially for class II HLA antigens. Female compared with male patients (60.3% vs 34.2%; P < .001) and retransplantation compared with first transplantation candidates of kidney transplantation (80.2% vs 41.1%; P < .001) showed a significantly higher PRA-positive rate. Retransplantation candidates (MFI 14,164) showed significantly stronger antibody strength than first transplantation candidates (MFI 5456) and those with single sensitization events of transfusion (MFI 4185) or pregnancy (MFI 5548; P < .001 for each).

Solid organ transplantation appears to have the strongest HLA alloimmunization effect followed by pregnancy and transfusion, especially for class II HLA antigens.