IDENTIFICATION OF HLA ANTIBODIES IN RENAL TRANSPLANT RECIPIENTS USING CLASS I AND CLASS II FLOW PRA BEADS.
          CL Murphey, B Blair, C Gonzalez, W Jackson, B White, J Morrisey, and S Mesa, Southwest Immunodiagnostics, San Antonio, Texas.
          In a continuing effort to accurately categorize and identify HLA antibodies we turned to the Flow Class I and Class II PRA beads (One Lambda) as a screening tool for our renal patients. We were particularly interested in screening our regraft recipients that are currently listed on our cadaveric transplant list. Fifty-two regraft patients were screened with both the Class I and Class II PRA beads as well as by cytotoxicity (antiglobulin - unseparated cells). 40 patients (77%) had PRA levels > 20% by AHG. 37 recipients (71%) had PRA levels > 20% by Flow Class I beads and 42 patients (81%) were positive with the Class II Flow PRA beads. Of these 52 patients, 73% (38 patients) were positive for both Class I and Class II , 6% (3 pts.) had only Class II antibody and 8% (4 pts.) had only Class I antibody present. 13% of the patients made neither Class I or Class II antibody. Of the 42 patients positive for Class II beads, 26 had PRA levels > 70% and 18 had PRA levels of > 90%. Additionally, for the recipients that had Class II antibody present, we are performing platelet absorptions and screening this absorbed sera against mini B cell panels by flow cytometry. To date, 4 patients have identifiable Class II antibodies to previously mismatched donor antigens. While the Flow PRA beads are very useful as a screening mechanism, some of the Class II PRA percentages were perplexing. One recipient (DR 4,13 DQ7 DR52,53) had a 93% Class II PRA level with the only donor mismatch being DR 103. Part of this may be due to the panel composition and antigen representation on the beads. This testing has verified the presence of Class II antibody in regraft recipients and the need for antibody identification in this patient population. In conclusion, we believe that the Class I and II Flow PRA beads by One Lambda are very useful in screening transplant recipients for HLA antibodies.