Acceptance of Walker 256 Carcinosarcoma by Neonatally Thymectomized G57 BL/6 Mice

Abstract

Comment and conclusions

Although palpable nodules, shown in some cases to contain tumor cells, developed in some but not all control C57 BL/6 mice injected with the Walker 256 tumor of rats, these nodules regressed and finally disappeared within 2 to 4 weeks. Thus, the Walker tumor grows briefly in C57 BL/6 mice, but under the conditions of these experiments it was soon rejected by the host.

It would not have been surprising had the tumor been rejected more slowly when given to normal mice less than 1 day old or even 4 to 6 days old than when given to older animals, because such young mice are relatively incompetent immunologically at this age. Indeed, if circumstances were right, development of acquired immunologic tolerance might be possible(13). In the present experiments, palpable nodules developed in a higher percentage of mice less than a week old than was the case in older control animals, and the nodules usually became larger in the young mice before regression occurred. In our experiments, the absence of evidence of acquired tolerance developing in the very young mice might be related to the dosage of tumor cells, but to explore this relationship further studies would be needed in which larger doses of tumor cells were used.

Clearly, thymectomy performed within 24 hours of birth, but not at 35 to 40 days of age, permitted Walker 256 tumor cells to grow in C57 BL/6 mice and usually to kill the host within 28 days.