Donor lymphocyte infusion is an alternative treatment for Epstein-Barr virus (EBV)-associated lymphoproliferative disorders (LPDs) but with risk of graft-versushost diseases (GVHDs). According to the fetal-maternal microchimerism tolerance, we assumed that maternal lymphocyte infusion may be effective without causing GVHD. In 54 cases when a child required cytotherapy or hematopoietic stem cell transplantation, we studied the mother for child-mother microchimerism with use of insertion-deletion polymorphisms as