PLACENTAL BLOOD AS A SOURCE OF HEMATOPOIETIC STEM-CELLS FOR TRANSPLANTATION INTO UNRELATED RECIPIENTS

Background Transplantation of bone marrow from unrelated donors is lim ited by a lack of HLA-matched donors and the risk of graft-versus-host disease (GVHD). Placental blood from sibling donors can reconstitute hematopoiesis. We report preliminary results of transplantation using partially HLA-mismatched placental blood from unrelated donors. Method s Twenty-five consecutive patients, primarily children, with a variety of malignant and nonmalignant conditions received placental blood fro m unrelated donors and were evaluated for hematologic and immunologic reconstitution and GVHD. HLA matching was performed before transplanta tion by serologic typing for class I HLA antigens and low-resolution m olecular typing for class II HLA alleles. In donor-recipient pairs who differed by no more than one HLA antigen or allele, high-resolution c lass II HLA typing was done retrospectively. For donor-recipient pairs who were mismatched for two HLA antigens or alleles, high-resolution typing was used prospectively to select the best match for HLA-DRB1. R esults Twenty-four of the 25 donor-recipient pairs were discordant for one to th ree HCA antigens. In 23 of the 25 transplant recipients, th e infused hematopoietic stem cells engrafted. Acute grade III GVHD occ urred in 2 of the 21 patients who could be evaluated, and 2 patients h ad chronic GVHD. In vitro proliferative responses of T cells and B cel ls to plant mitogens were detected 60 days after transplantation. With a median follow-up of 12 1/2 months and a minimal follow-up of 100 da ys, the overall 100-day survival rate among these patients was 64 perc ent, and the overall event-free survival was 48 percent. Conclusions H LA-mismatched placental blood from unrelated donors is an alternative source of stem cells for hematopoietic reconstitution in children. (C) 1996, Massachusetts Medical Society.