Abstract
Summary
1) Supernatant fluid from 105,-000 g centrifugation of Ak leukemic tissues caused a multiplicity of tumors and a variety of non-neoplastic lesions in 87.5% of AkR mice injected shortly after birth. 2) Evidence reported here, and obtained by others (notably Gross, Stewart et al.) suggests that lesions described here, are caused by a pluripotent agent (to be called P virus) which is distinct from that which causes leukemia (to be called L virus). 3) The relationship between P and L viruses is conjectural. On the basis of evidence presented, we suggest as a working hypothesis that the P virus is of the parasitic type, is very small, and spreads by natural means. It is usually masked, and may be inhibited in tissue extracts by some macromolecular particles. The L virus is larger, has a more limited host range, and may be related to the genome of the leukemic cell.
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