Abstract
The characteristics of a spontaneous lymphoblastic leukemia occurring in CFW inbred mice are described. This tumor develops in about 5 percent of more than 11 month-old mice, more frequently in females. It is successfully transplanted by subcutaneous or intraperitoneal injection of cells suspension in animals of the same strain only. Both primary and transplanted leukemias show a varying proportion of cells with aneuploid chromosome numbers, ranging from 39 to 42. Electron microscopic observations of the leukemic cells reveal the presence of intracytoplasmic virus-particles, usually situated in the Golgi zone. The virus has two membranes; the diameter of the outer membrane is about 75 mμ. The virus is similar to the A2 particles described by Dalton. The subcutaneous injection of cell-free filtrates of leukemic cells in less than 24 hour-old CFW mice was followed by the appearance of leukemia only in a limited number of mice. A preliminary investigation of the possible cross-resistance between this leukemia and that induced with Moloney virus in C3H mice showed that pretreatment with Moloney leukemia cells in CFW mice resulted in resistance against a subsequent isograft of CFW leukemia. However, a marked resistance occurred also following the pretreatment of CFW mice with lymphoid cells of normal C3H mice.
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