Ontogenic development and biological role of fetal suppressor cells and newborn contrasuppressor cells in mice.

Following essential information concerning immunoregulatory cellular circuits in adult animals, the ontogeny of mouse suppressor and contrasuppressor systems are described. Fetal suppressor T cells found in the spleen of fetal and newborn mice less than 2 days of age are capable of inhibiting T-dependent immunological responses. The abrupt loss of suppression is due to contrasuppressor activity of the newborn thymus and can be prevented by neonatal thymectomy or reversed by removing cells with anti-contrasuppressor I-J serum. The possible biological significance of fetal suppressor cells and newborn contrasuppressor cells are briefly discussed.