Development and Regression of Murine Leukemia Induced by Friend Virus Complex 1

Summary Injection of a large dose (5000 FFU) of Friend virus complex (FV) lead to rapid development of leukemia and to death in A/J mice. Leukemia developed at a slower rate in A/J mice inoculated with 5 FFU of FV. A very small dose (0.5 FFU) of the same virus caused slow development of leukemia that later regressed in most A/J mice (73%). In (A/J X C57BL/6J) F1 and their reciprocal hybrids, leukemia developed rapidly after the injection of 500 FFU, but regressed in 97% of the mice. The authors thank Drs. W. D. Sawyer, S. Sirisinha and L. C. Olson for their helpful advice.