Search

HLA loss in hematologic malignancies is rare at diagnosis but may occur in leukemic cells at disease relapse. Although HLA mismatched hematopoietic cell transplant (HCT) is useful in exploiting graft vs. leukemia (GvL) effects, alloreactive T cells may exert immune pressure on leukemic cells, leading to immune escape. Roughly 10–30% of relapses after HLA mismatched hematopoietic cell transplant (HCT) involve loss of recipient-specific HLA genes, thereby rendering leukemic cells resistant to donor GvL effects. The use of alloreactive T cells, i.e., donor lymphocyte infusions (DLI) to control relapse following HCT will not be effective in the context of recipient-specific HLA loss and will instead carry all the risk of graft versus host disease (GvHD). Additionally, the source of the lost HLA, maternal or paternal, is important in informing the best donor choice for rescue HCT. The growing body of evidence, together with developments in laboratory testing for genomic loss of HLA, has highlighted the importance of routine testing for HLA loss in patients who relapse post HLA-mismatched HCT. Assessment of HLA loss allows transplant centers to make quick decisions regarding the most appropriate therapies and/or alternative donor selection for rescue HCT. [ABSTRACT FROM AUTHOR]

Novel allele, DPB1*1049:01, is a one nucleotide variant of DPB1*03:01:01:01. [ABSTRACT FROM AUTHOR]

A pediatric patient with acute myeloid leukemia was referred to our institution for investigational therapy after disease relapse following a mismatched unrelated donor hematopoietic cell transplant (HCT). Prior to second HCT, the patient's serum was negative for antibodies to class I and class II HLA. Eight days after receiving a maternal donor haploidentical transplant, the patient became platelet refractory and highly sensitized to multiple class I HLA. Serum from the patient's mother was positive for the strongest antibodies present in the patient, suggesting the antibodies were donor-derived. Patient sera showed magnified and expanded sensitization over time in the context of 100% donor chimerism and despite undetectable circulating B cells. Escalating sensitization suggests active transfer of rituximab-resistant antibody-producing passenger lymphocytes from a haploidentical donor to a transplant recipient at the time of progenitor cell infusion. Evaluation of donor sensitization status may be a consideration prior to HLA mismatched HCT. [ABSTRACT FROM AUTHOR]