Thymic Hypoplasia due to a Bis‐diamine

Bis(dichloroacetyl)diamine is capable of producing characteristic congenital malformations in high incidence. Wistar rats were given 200 mg/day of bis‐diamine via a gastric tube on gestation days 9, 10 and 11. The fetuses of 14, 16, 18, 20 days and new born rats were examined using light and electron microscopes as well as rat T‐cell surface markers. The thymus rudiment in rats treated with bis‐diamine has been compared to the normal at each stages. A high incidence of aplasia or hypoplasia of the thymus was observed in treated groups. Histological studies of those revealed a short delay in appearance of lymphocytic cells in the thymus, which initially were blast like and later small lymphocytes, and also a delay in cortical and medullary differentiation of the thymus. Immunohistological studies using anti rat T‐cell monoclonal antibodies confirmed the histological findings which show a delay of the development of the thymus. Bis‐diamine induced anomalies were similar to those of the human primary immunodeficiency syndrome, particularly the DiGeorge syndrome.