Impaired host defense against XC cell-induced tumors in thymectomized and in bursectomized chickens.

XC cells originally derived from the tumor of a rat previously inoculated with the Prague strain of Rous sarcoma virus were used to induce tumors in chickens surgically thymectomized or bursectomized in the newly hatched period. Thymectomized chickens had a significantly higher incidence of tumors, larger tumors, and a higher tumor mortality, compared with control chickens, when both groups were given 5 X 10(6) XC cells into the wing webs. Bursectomy could significantly influence the tumor size only. It appeared that the capacity of XC cells to induce tumors and the growth of such tumors were subject to immunological influence, with the thymus playing a major and the bursa of Fabricus a minor role under the conditions used.