P153 Donor specific anti-HLA antibodies in haplo-transplant- What to tell the clinician?

Case 55 year Caucasian female with AML was evaluated for stem cell transplant (SCT). Patient had no 10/10 matched siblings or unrelated donors and thus haplo-SCT was considered. Investigations High resolution HLA typing was performed on the recipient and donor. Recipient sera was screened for anti-HLA antibodies by single antigen beads (LabScreen, One Lamda). MFI > 1000 was the cutoff. Findings Recipient and donor typing: Download high-res image (73KB) Download full-size image SAB demonstrated patient was alloimmunized with DSA to HLA-DRB1 ∗ 04:04. As this was an antibody to ‘self’ antigen, after testing a different sample and vendor kit, it was thought to be a due to passive transfer of antibodies from blood transfusions. Serial SAB initially demonstrated decreasing DSA: Download high-res image (40KB) Download full-size image However, Feb results were concerning about this being a true antibody. Recipient typing ruled out a rare null DRB1 ∗ 04 allele. Flow crossmatch with donor cells and all recipient sera were negative. Susbsequent testing after treating the beads with fetal calf serum (FCS) resulted in the removal of anti-HLA specificity to self. This change in reactivity was not seen in the positive control. Download high-res image (150KB) Download full-size image Based on these recipient was transplanted in March 2016. Recipient engrafted by 21 days and continues to do fine. Conclusion This case demonstrates that SAB assay may show non-specific reactivity that can be blocked by FCS treatment. Detailed laboratory investigation allowed correct analysis and speedy transplant.