IST group: ATG (Thymoglobuline®, Genzyme) 3.5mg/kg/d×5d plus oral cyclosporine A (CSA) Cord blood transfusion group: In addition to the same dose and course of ATG and CSA , one unit of cord blood having no more than 2 HLA-A, B or DRB1 mismatches is transfused 24h after last dose of ATG administration.