The participation of neural crest derived mesenchymal cells in development of the epithelial primordium of the thymus.

The purpose of this study was to correlate the contributions by derivatives of the neural crest with the development of the epithelial primordium of the thymus. The monoclonal antibody E/C8 was used to localize derivatives of the neural crest in chick embryos. Neural crest was ablated by microcautery of neural folds. Evaluation of thymic development was carried out on serial sections of embryos sacrificed on the sixth day of incubation. The size of the epithelial thymic primordium was smaller in experimental animals than in shams. E/C8-immunoreactivity was concentrated around the periphery of the primordium. It was determined, by quantifying reaction product using the Core-SCAN computer color analysis program, that the amount of immunoreactivity was decreased after ablation of neural crest. Statistical analysis showed that the quantity of reaction product was positively and significantly correlated with the size of the thymic primordium. It is concluded that mesenchymal derivatives of the neural crest, through participation in the early development of the epithelial primordium, play an important role in thymic development, and therefore with development of the immune system.