Growth and differentiation in culture of leukemic leukocytes from a patient with acute myelogenous leukemia and re-identification of type-C virus.

Conditioned medium from a culture of whole human embryo cells stimulated prolonged exponential growth in suspension culture of leukocytes from a patient with acute myelogenous leukemia. Ten to 20% of the cultured cells consistently differentiated into mature granulocytes including neutrophils, eosinophils, and basophils. The proportion of lymphocytes declined after culturing, and tests for Epstein-Barr virus antigens were negative. An abnormality of a G group chromosome was observed in some metaphases from the patient's fresh bone marrow and from the cultured leukocytes, indicating growth in vitro of leukemic cells. After 4-10 weeks in culture, a budding type-C virus was continuously released by the cultured leukocytes, predominantly by undifferentiated blast cells. This virus was originally identified in three different cultures of a peripheral blood specimen obtained at the time of diagnosis. Subsequently, this virus was identified by reverse transcriptase (RNA-dependent DNA polymerase) assays and by electron microscopy in cultured leukocytes from a bone marrow specimen obtained 14 months later from the same patient. Virus produced by cultures of both specimens was closely related, if not identical, to the woolly monkey type-C virus.