Flow cytometric assessment of HLA alloantibodies.

Antibodies against HLA molecules are formed in response to exposure to foreign HLA molecules, which can occur as a result of blood transfusion, pregnancy, or transplant. Blood components, particularly those containing cellular elements, are the most common cause of HLA antibodies. This unit describes technical aspects of the flow cytometric crossmatch (FCXM), flow cytometric microparticle assays, and cell-based flow cytometric screening assays. The collective goal for these assays is to clearly identify the presence of HLA antibody, determine the titer of antibody, and elucidate the specificities (i.e., HLA antigens) to which they will react. Knowledge of this information is critical for organ allocation and accurate assessment of the immunological risk for a patient at the time of transplantation. In addition, the identification of HLA antibodies in blood components may be useful in planning appropriate transfusion support strategies for selected patients.