Persistent production of deficient form of friend virus.
D000818:Animals; D005615:Freezing; D005622:Friend murine leukemia virus / Q000276:immunology / Q000472:pathogenicity; D051379:Mice; D008854:Microscopy, Electron; D009368:Neoplasm Transplantation; D009500:Neutralization Tests; D012513:Sarcoma, Experimental / Q000276:immunology