Time of Action of the Thymus in the Irradiated Adult Mouse

Abstract

RECENT interest in the thymus has derived largely from the discovery that in both neonatally thymectomized and thymoctomized irradiated adult mice the development of the ability to respond to primary antigenic challenge is seriously impaired^4,5. No satisfactory explanation exists for these findings, but it has been shown that thymuses taken from new-born mice and grafted into immunologically incompetent mice will restore normal or near-normal competence⁴. Further, in neonatally thymectomized mice this effect has been achieved even though the grafted thymus has been enclosed in a ‘Millipore’ diffusion chamber, which precludes the possibility of ingress and egress of cells⁶. This suggests that thymic function involves a humoral factor. The experiments presented here concern in part attempts to devise a test system for such a factor and in part to assist understanding of the time of action of the thymus in the restoration of immunological competence after irradiation.