Search for "indicators" of neoplastic conversion in vitro.

Certain responses of mouse and hamster cells to polyoma virus were examined with respect to their specificity as "indicators" of neoplastic conversion in vitro. These responses included the development of transplantation antigens and changes in morphologic growth pattern, cytology, karyology, rates of proliferation, and glycolytic activities. Under limited conditions, i.

THYMUS: ROLE IN RESISTANCE TO POLYOMA VIRUS ONCOGENESIS.

Mice of the C57BL strain are highly resistant to the oncogenic property of LID-1 polyoma virus, but complete thymectomy within 24 hours of birth rendered these mice susceptible. In thymectomized mice inoculated with adult syngeneic spleen cells, the capacity to resist oncogenesis was restored. The results add further weight to the concept that induction and progression of tumors by polyoma virus has an immunologic basis.

HUMORAL THYMIC FACTOR IN MICE: FURTHER EVIDENCE.

Mice of the C3H and DBA strains thymectomized at birth showed a consistent and striking suppression of antibody production (hemolysin response) to sheep erythrocytes. When cell-tight Millipore diffusion chambers containing syngeneic thymic tissue were implanted intraperitoneally, the capacity of these neonatally thymectomized mice to respond to this antigen was restored. The pattern of response and the mean titer were similar to the pattern and mean titer observed in neonatally thymectomized mice bearing subcutaneous grafts of syngeneic thymic tissue.

Lymphocytic Choriomeningitis Infection in Neonataily Thymectomized Mice Bearing Diffusion Chambers Containing Thymus.

Normal, nonoperated Swiss mice which had been inoculated intracerebrally with lymphocytic choriomeningitis virus showed a 100-percent mortality within 8 days after virus challenge. Neonatally thymectomized mice, with or without empty intraperitoneal diffusion chambers, were protected from the lethal effects of the virus, with no animals dying within 14 days after inoculation. Cell-tight Millipore diffusion chambers containing newborn thymic tissue, implanted intraperitoneally into neonatally thymectomized mice, restored the susceptibility of 52 percent of these mice to the lethality of the virus infection.