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. These data are consistent with the concept that thymic tissue within the chamber produced a specific diffusible factor that enabled the thymectomized animal to establish immunologic competence.