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Response of Bone Marrow to MC29 Avian Leukosis Virus in Vitro¹

Department of Surgery, Duke University Medical Center, Durham, North Carolina 27706

Infection of avian bone marrow with strain MC29 leukosis virus in vitro resulted in infection, elaboration of virus, and growth of characteristic cells. Newly liberated virus with the infectious and neutralization properties of strain MC29 agent and growth of the cells were demonstrable 48 hr and 5–6 days respectively after infection. Studies by light and electron microscopy revealed similarities between the bone marrow cells and the myeloid elements (myelocytes) of myelocytomatosis notable in the relatively low nucleus/cytoplasm ratio; very large nucleolus; and ribosome-rich cytoplasm with a dense gray (protein) matrix and a grainy or "ground glass" appearance. Such cells differed markedly in these morphologic aspects from the myeloid cells (myeloblasts) of myeloblastic leukemia induced by BAI strain A. They also differed in their short-lived growth of 3–4 weeks when compared with myeloblast proliferation indefinitely in culture. The cells were similar to chick embryo cells morphologically altered by strain MC29 because of the characteristically large nucleolus, the high concentration of cytoplasmic ribosomes, and the slight rough endoplasmic reticulum. A notable difference was the high content of diffuse chromatin in the chick embryo cells and the reverse proportion of condensed chromatin in the myelocytes. The various aspects of strain MC29 specificity of influence on cell response are discussed.

¹ This investigation was supported by USPHS Grant C-4572; by the Annie Mabel Sherris Memorial Grant for Cancer Research from the American Cancer Society, Inc.; and by the Dorothy Beard Research Fund.

² Present address: National Cancer Institute, NIH, Bethesda, Maryland 20014.

Received 2/13/69. Accepted 3/21/69.