High Rate of Passenger Lymphocyte Syndrome after ABO Minor Incompatible Lung Transplantation.

Rationale: Passenger lymphocyte syndrome (PLS) may complicate minor ABO mismatched lung transplantation (LuTX) via donor-derived red cell antibody-induced hemolysis.Objectives: To ascertain the incidence and specificity of PLS-relevant antibodies among the study population as well as the dynamics of hemolysis parameters and the transfusion requirement of patients with or without PLS.Methods: In this cohort study, 1,011 patients who received LuTX between January 2010 and June 2019 were studied retrospectively. Prospectively, 87 LuTX (July 2019 to June 2021) were analyzed. Postoperative ABO antibody and hemolytic marker determinations, transfusion requirement, and duration of postoperative hospital care were analyzed. Retrospectively, blood group A recipients of O grafts with PLS were compared with those without.Measurements and Main Results: PLS affected 18.18% (retrospective) and 30.77% (prospective) of A recipients receiving O grafts, 5.13% of B recipients of O grafts, and 20% of AB patients receiving O transplants. Anti-A and anti-A1 were the predominant PLS-inducing antibodies, followed by anti-B and anti-A,B. Significantly lower hemoglobin values (median, 7.4 vs. 8.3 g/dl; P = 0.0063) and an approximately twice as high percentage of patients requiring blood transfusions were seen in PLS. No significant differences in other laboratory markers, duration of hospital stay, or other complications after LuTX were registered.Conclusions: Minor ABO incompatible LuTX recipients are at considerable risk of developing clinically significant PLS. Post-transplant monitoring combining red cell serology and hemolysis marker determination appears advisable so as not to overlook hemolytic episodes that necessitate antigen-negative transfusion therapy.

Donor-derived anti-HLA antibodies in a haploidentical hematopoietic cell transplant recipient shortly after transplant.

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.