Relationships Between Lymphocytic Choriomeningitis Virus, Amethopterin, and an Amethopterin-Resistant Lymphocytic Neoplasm in Mice

Abstract

Amethopterin resistance was developed in the tetraploid lymphocytic neoplasm P288 by serial transfer of cells of the amethopterin-sensitive stem line through amethopterin-treated mice. The character of amethopterin resistance remained stable and heritable following the transfer of cells, for many transfer generations, through untreated mice. Lymphocytic choriomeningitis (LCM) virus did not influence this resistance since it was never found in the sensitive stem line or in the amethopterin-resistant sublines. However, the resistant subline (P288/AmR-II) was infected intentionally with the virus of LCM in a single exposure in vitro and carried it, as a passenger, through 39 successive transfers. Passage of this contaminated tumor through mice immune to LCM caused the virus to disappear, insofar as the tests were capable of detecting it, but virus did not disappear from amethopterin-treated immune mice bearing the tumor. It was also found that the resistant subline (free of LCM) of neoplasm P288 could grow progressively and kill certain mice of foreign strains when such mice were treated with amethopterin.