Abstract: The present invention relates to a method for protecting hematopoietic stem cells from the myelotoxicity of chemotherapeutic drugs or radiation therapy, which comprises, administering to a subject a therapeutically effective amount of transforming growth factor beta 1 for protecting bone marrow from the myelotoxicity of chemotherapeutic drugs or radiation therapy. The TGF.beta.1 may be administered prior (e.g. 24 hours) to the administration of the chemotherapeutic drugs or radiation therapy. Preferably, the TGF.beta.1 is administered to the subject in an amount of about 5 .mu.g to 25 .mu.g per kg body weight. The patient or subject of the present invention may be a mammal (e.g. human, domestic animal such as horse, cow, dog, cat or pig) and is preferably a human being. The mode of administration is either by interfemoral arterial, interperitoneally or subcutaneously, and preferably is by injection.

Abstract: A novel human megakaryocytopoietic growth promoting activity factor capable of stimulating the growth of megakaryocytes and augments the differentiation or maturation of megakaryocytes. Also provided are processes for obtaining the factor in homogeneous form and producing it by recombinant genetic engineering techniques.