109-P

Abstract

Aim Hematopoietic stem cell transplant patients are tested for HLA antibodies if potential donors are unrelated donors with mismatched HLA antigens. If transfusions occur after the antibody test but before the transplant can occur, additional HLA antibody tests are recommended. In this case, a patient was screened for antibodies on three different dates. Methods Serum samples were screened for HLA antibodies using the One Lambda LABScreen Mixed kit on a Luminex instrument. Class I antibody specificities were identified using the One Lambda Single Antigen Bead kit. Results Antibody screening tests done on days 0, 10, and 45 were positive for HLA class I and negative for class II antibodies. The antibody identification test on day 0 showed a Bw4 specificity that reacted with all Bw4 HLA-B antigens plus the four Bw4 positive A locus antigens: A23, A24, A25 and A32. Normalized median fluorescence intensity of the Bw4 positive antigens ranged from 3702 for B ∗ 51:02 to 753 for A ∗ 24:02. On day 10, normalized MFI ranged from 2667 for B ∗ 51:02 to 620 for A ∗ 24:02, and on day 45, from 1160 for B ∗ 49:01 to 130 for A ∗ 24:02. Half life of the normalized MFI values was calculated to be 25.6 days. The patient’s HLA phenotype had no A or B antigens with the Bw4 epitope (A ∗ 01:01, A ∗ 02:05, B ∗ 08:01, B ∗ 15:03). One unrelated donor had a mismatched A ∗ 24:02 allele that was borderline incompatible with the initial antibody results, but after the decline in A ∗ 24:02 reactivity that donor was no longer incompatible. Conclusions This patient had HLA antibodies with a half life similar to the half life of passively acquired immunoglobulins, possibly from a blood component transfusion. Even though donor specific antibody reactivity was demonstrated initially, this patient was apparently not producing the antibodies. Donor specific antibodies are incompatible with donors that have mismatched HLA antigens, but if passively acquired they may decline over time to an acceptable level.