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Viruses and the pathogenesis of human leukemia.

The first part of this review deals with some new ideas on the nature of acute myelogenous leukemic cells. It is shown that the bloc in the differentiation process which characterizes these malignant cells can, to a certain extent, be overcome by some differentiation promoting proteins which are described. The finding that leukemic cells may respond to these "factors" indicates that these cells are not completely autonomous. Further studies in this field will clarify some biochemical and virological questions related to malignant transformation. In the second part, information on RNA tumor viruses is presented and their role in animal leukemias and possible involvement in humans are discussed. Whereas there is firm evidence for the presence of oncornavirus-related information in the human population, no cohesive pattern has emerged allowing definitive etiological inferences.