F8 and hemophilia A: We observed previously that human hematopoietic cells could serve as a primary tissue source for the synthesis of a functional form of human BDDFVIII (FVIII:C) within tissue-cultured human megakaryocytes12, 36, in peripheral blood platelets isolated from mice xenotransplanted with BDDFVIII-transduced human G-PBC12, and in a murine model for haemophilia A that received a transplant of BDDFVIII-transduced bone marrow16.