(O1-3) Non-T-cell depleted HLA haploidentical stem cell transplantation in advanced hematological malignancies based on the feto-maternal immunological tolerance

Feto-maternal microchimerism suggests that immunological tolerance exists between mother and fetus. Based on this hypothesis, we performed haploidentical stem cell transplantation (SCT) without T-cell depletion (TCD) in nine patients with advanced hematological malignancies. There were six males and three females, their ages ranging from 17 to 55 years. Two patients had CML at blast crisis, three had ALL/LBL, two had NHL, and two had MM/PCL. All patients were in relapse or refractory stages. HLA incompatibilities for GVHD direction included three loci mismatches in six patients, and two loci mismatches in three patients. A HLA-nested polymerase chain reaction with sequence-specific primer typing demonstrated chimeric cells in eight of nine donors. The conditioning regimen consisted of CA/CY/TBI in six patients, BU/CY in one patient, and Flu/L-PAM in two patients. The median number of CD34+ cells infused was 2.25 × 106/kg. The prophylaxis against graft-versus-host disease (GVHD) was tacrolimus with minidose methotrexate (5mg/kg, on days 1, 3, and 6). Engraftment was obtained in all patients. An acute GVHD of less than or equal to grade 2 developed in all patients except one who developed tacrolimus encephalopathy. Chronic GVHD developed in four of seven evaluable patients. Four patients died; one with fungal pneumonia, one with GVHD after cessation of taclorimus because of relapse and two with disease progression. Five patients survived, with one patient being in complete remission (+75～+648). These observations suggest that haploidentical SCT based on the feto-maternal immunological tolerance without TCD is possible.