Interdependence of thymic and neuroendocrine functions in ontogeny.

The immunological blockade of the adenohypophysis of athymic nude mice bearing allogeneic skin grafts prevents the reconstitution of transplantation immunity when such animals grafted with thymus, and the grafts are permanently accepted. Newborn and adult athymic mice have markedly diminished levels of prolactin in blood and abnormally high levels of luteotropic hormone. Implantation of the thymus normalizes blood levels of these two hormones. These findings affirm the role of the thymus in the organization of the maturing brain for endocrine functions and identify prolactin as one of the hormones which play a major role in immune differentiation in early ontogeny.