Monday, September 27, 2010 2:00 PM - American Society for ...

to Mean Channel shift (MCS) of fluorescence intensity. Cut-off value used for positive FXM was 60 and75 for T and B cells respectively. We examined 262 crossmatches that were performed during the period ofNovember-March 2010.Results: A summary of FXM results and DSA is shown in Table 1. Of the 262 FXM, 8.8% were positivewith MCS>100 and had anti-HLA Abs; 35% of these appear to be due to anti-DP or DRB3 allele-specificantibodies and the remaining were due to weak DSA (MFI: 1000-3000). 44% (18/41) of positive FXM withMCS>100 were not associated with DSA (MFI cut-off value500), FCXMs were performed when donor cells were available (n=35). Outcomes werecompared overall and between FCXM- vs unsensitized groups.Results: Table 1[table1]Conclusions: When DSA is present, patients are more likely to experience AMR than unsensitizedpatients. Collectively, the DSA+/FCXM+ patients have more AMR and lower CrCL than DSA+/FCXMpatients.This latter group still has significant AMR compared to unsensitized patients. Thus,DSA+/FCXM- recipients represent a higher risk transplant than DSA- recipients. Nonetheless, ∼50% ofDSA+ recipients (whether FCXM + or -) were rejection free, meaning that certain donor:recipientincompatibilities are acceptable. Further studies should address which elements dictate good outcome.12-PA NOVEL HLA CLASS I SINGLE ANTIGEN BEAD PREPARATION ELIMINATES FALSEPOSITIVE REACTIONS ATTRIBUTED TO NATURAL ANTIBODIES – IN THE SERA OFNORMAL MALES AND PRE-TRANSPLANT PATIENTS.Nadim R. El-Awar 1 , Paul I. Terasaki 2 , Ali Hajeer 3 , Afzal Nikaein 4 , Matthew Averly 1 , Judy Hopfield 1 , AnhNguyen 1 . 1 Research II, One Lambda Inc., Canoga Park, CA, USA; 2 Terasaki Foundation Laboratory, LosAngeles, CA, USA; 3 King Fahad National Guard Hospital, Riyadh, Saudi Arabia; 4 Texas MedicalSpecialty, Inc., Dallas, TX, USA.Aim: Single antigen (SA) beads have been shown to produce “false” irrelevant reactions in the sera of nonimmunizednormal males. We tested a new bead preparation produced to eliminate these reactions.Methods: 30 normal sera and 46 sera from pre-transplant (pre-Tx) patients were tested with SA beads, EBtreated beads and Clean SA Beads (patent pending) - free of denatured class I antigens (One Lambda Inc.).All MFI values >1000 of the adjusted and normalized trimmed mean were considered positive.Results: Examples of HLA class I specificities of normal male (A) and pre-Tx (B) sera are shown.Reactions of the Clean Beads become negative as compared to the reactions with SA beads and reactionswith the EB treated beads are positive indicating the antibodies target cryptic epitopes. For example.,B0702 (A) has 5,345 MFI with SA beads, 352 MFI with the clean beads, and 7,625 MFI with the EB beads.2/13 (15%), 20/24 (83%), and 5/6 (83%) of the normal sera specificities for the A, B, and C locusrespectively are negative with the clean beads.[figure1]