GROWTH OF HETEROLOGOUS TUMOUR CELLS IN CHICK EMBRYOS

In order to investigate the factors responsible for the varying capacities of different tumours to grow in contact with the tissues of embryonated hen's eggs the growth of tumour cells derived from rats, mice and hamsters following intravenous injection via the chorioallantoic vein has been examined. Tumours can be divided into two fairly distinct groups on the basis of their capactiy to grow following injection into 11 day embryos. Those tumours which had lost their strain specificity in the species of origin grew vigorously in many organs of the chick embryo and also in the chorioallantoic and yolk sac membranes. Most of the tumours which had retained their strain specificity did not grow in any organs except the brain, even with maximum tolerated inoculum. Immunosuppressive procedures including X-irradiation of the embryos, treatment with cortison and chemical bursectomy did not significantly enhance or inhibit the growth of representative tumours from both groups, indicating that host resistance was not associated with an active specific immune response. The use of younger embryos (7-8 days) enhanced the growth of all tumours, sometimes dramatically. It is suggested that the resistance of embryos to the growth of certain tumours is associated with the release of natural meternal antibodies from the yolk into the embryonic circulation during development. © 1969.