Abstract
Cells of the original line of lymphoma 6C3HED, which regularly prove susceptible to the effects of guinea pig serum in vivo, were cultured in Eagle's medium devoid of L-asparagine; after a latent period of 2 or more weeks, during which time the cell population declined markedly, some of the cells began to proliferate, and thereafter continued vigorous growth. On implantation into mice the proliferating cells were found, however, to have completely and permanently lost their susceptibility to the effects of guinea pig serum.