Host age dependency of regression of Rous sarcomas of chickens.

Tumors were induced in Regional Poultry Research Laboratory line 6 chickens inoculated in the wing web with Rous sarcoma virus the Bryan high-liter strain of pseudotype, at 1, 14, and 28 days of age. Tumor regression failed to occur in chicks inoculated at 1 and 14 days of age, but an incidence of regression of 50% was observed in chicks inocu lated at 28 days of age. Chick survival time postinoculation and the incidence of visceral métastaseswere directly re lated to chick age at inoculation. The age-dependent changes in the incidence of regression and métastases probably were associated with developing immunological maturity of the host.