Summary
A comparative study of the critical factors involved in the induction of tolerance to mouse tumors in rats treated after birth by intraperitoneal injections of mouse spleen, liver, and tumor cell suspensions has revealed that the induction and maintenance of tolerance is essentially conditioned by repeated inoculation of the antigen. Tolerance to mouse tumors was conferred on rats by spleen cells, provided the latter were administered in daily inoculations the first 10 days of life. The incidence rate of actively developing tumors and the duration of tolerance were directly related to the total dose of postnatally administered spleen cells. By the administration of a second course of large doses of spleen cells, tolerance could be maintained after the onset of recovery from paralysis. Similarly, tolerance could be reinduced by repeated inoculations of tumor cells in rats that had been sensitized by a mouse skin heterograft during the period of recovery from paralysis. Actively growing tumors developed in rats treated with nonviable liver cells during the first week of life and thereafter repeatedly reinoculated with tumor cells. Tolerance was induced by repeated inoculations of tumor cells administered during the first 3 to 5 days of life; a similar dose proved inefficient when administered in a single inoculation during the neonatal period.
The theoretical implications of these results are discussed.
Footnotes
- Received March 18, 1968.
- Accepted August 27, 1968.
- ©1969 American Association for Cancer Research.
Volume 29, Issue 2
