Chemical Carcinogen-Induced Transplantable Fibrosarcomas in Histocompatible Chickens. II. Effect of Age and Thymectomy on Tumor Incidence

Abstract

The incidence of primary fibrosarcomas 2–4 months after im injection of 7,12-dimethylbenz[a]anthracene (DMBA) was studied in normal, neonatally thymectomized and bursectomized SC (B2/B2) chickens. The tumor incidence was not significantly increased in thymectomized chickens inoculated at 1 week of age, but thymectomized animals inoculated at 4 weeks of age developed a higher incidence of tumors than did controls. Bursectomy did not affect tumor induction. Whereas thymectomy and bursectomy clearly reduced T- and B-cell immune responses, respectively, neither the carcinogen nor the presence of tumor had a detectable effect on the immune response. The effect of varying the age of chickens at the time of carcinogen injection was also studied. DMBA injected into chickens at 8–12 weeks of age produced a significantly lower incidence of tumors than did a similar dose of DMBA injected into chickens at 1–4 weeks of age. Thus DMBA-induced tumors in the chicken may present an interesting model for studies on immune surveillance.