ANTI-DONOR ANTIBODY QUANTITATION FOR PRE- AND POST-TRANSPLANT MONITORING OF A 100% PRA HEART RECIPIENT.

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ANTI-DONOR ANTIBODY QUANTITATION FOR PRE- AND POST-TRANSPLANT MONITORING OF A 100% PRA HEART RECIPIENT.
Ruby Siegel MS, CHT , Ellen Klohe PhD and Diane Eklund MD . Spokane WA, Inland Northwest Blood Center, 99201, HLA Laboratory .

A unique method to quantitate donor-specific antibody combined with plasma-exchange/IVIG protocols and cytolytic B cell therapy (Rituxan™) was instrumental in the successful transplant of a 100% Class I PRA heart recipient. FlowPRA™ Class I Single Antigen assays (One Lambda, Inc.) were acquired on a FACSCalibur™ flow cytometer and analyzed with CellQuest™ software (Becton-Dickinson). A numerical value indicating the amount of antibody bound to each antigen was determined by the mean FL1 (FITC) fluorescence of each bead group. Data were entered into a spreadsheet developed by Puget Sound Blood Center, incorporating formulas that provide a quantitative assessment of patient antibody relative to the negative control and control beads. Patient channel shifts > 80 (1024 scale) indicated a positive result. Inhibition of specific HLA antibodies was tracked in the patient's sera during pre-transplant IVIG therapy. This allowed acceptance of a 6-antigen mismatched heart that was predicted to be compatible with post-IVIG sera. Intra-operative plasma-exchange was performed as an extra precaution, since the transplant was performed prior to the availability of crossmatch results. Despite a compatible flow crossmatch, donor-specific antibody appeared within 10 days post-transplant. Although weak C4d and fibrin deposition was noted on biopsy, the patient remained stable. Rising donor-specific antibody levels prompted plasma-exchange, IVIG and finally Rituxan™ therapy. Donor-specific antibodies became undetectable within 2 weeks of Rituxan™ therapy and have remained so. This method of flow bead analysis allowed quantitation of antibody against mismatched donor antigens, early detection of potential humoral rejection, correlation with biopsy findings and feedback on the patient’s response to immunosuppressive therapies.