Unappreciated risk factors for transplant patients: HLA antibodies in blood components

One of the more aggressive approaches in renal transplantation is the use of plasmapheresis (PP) and intravenous immunoglobulin to eliminate donor-directed human leukocyte antigen (HLA) alloantibodies. A potential complication of a PP protocol is iatrogenic hypocoagulability resulting from the removal of coagulation factors. To prevent bleeding, hypocoagulable patients may require transfusions with fresh frozen plasma (FFP) and/or cryoprecipitate (Cryo). Although HLA alloantibodies in these components have been linked to complications, such as transfusion-related acute lung injury (TRALI), whether they cause complications following transfusion into allograft recipients is unknown. The incidence of complications would be dependent, in part, upon the frequency of HLA alloantibodies in the various blood components. In this study, segments from 77 units of FFP, 66 units of Cryo, 106 units of packed red blood cells (RBCs), and 59 units of apheresis platelets (Plts) were tested for antibodies to HLA class I and class II antigens using FlowPRA, an HLA antigen-specific flow cytometric assay. On average, 22% of blood components tested contained HLA alloantibodies, tenfold greater than previously reported. This unappreciated frequency of HLA alloantibodies in blood components may pose a risk to transplant patients requiring transfusions by promoting allograft dysfunction or loss.