P441 - High resolution HLA matching associated with decreased mortality after unrelated bone marrow transplantation

Abstract

As compared with related HLA-identical sibling donors, bone marrow transplantation (BMT) with phenotypically HLA ABDR-compatible unrelated donors is associated with increased mortalii. This may be due to hidden HLA incompatibiliiies not detected by conventional typing. We have analyzed 44 unrelated patient-donor pairs who were matched for HLA-A, -B, and -DR by routine tissue typing. Our comprehensive HLA typing approach consisted of serology, cytotoxic T-cell precursor (CTLp) tests, T-cell cloning, oligotyping, and DNA sequencing. Using these techniques, we identified numerous HLA allele mismatches not detected by the previously applied routine typing. Twenty-four patientdonor pairs were highly matched and had a low CTLp frequency, whereas the remaining 20 pairs were allele-mis-