The interaction between Mycobacterium bovis (BCG) and genotype of chicken in increasing the percentage of regression of Rous sarcomas.

Four breeding groups of chickens were inoculated in the wing-web with Rous sarcoma virus at 8 weeks of age. Treated birds were given a single dose of live organisms of a mile strain of Mycobacterium bovis of variety Calmette Guerin (BCG) as a subcutaneous inoculation adjacent to the emerging tumor. Control birds received no BCG. The breeding groups of chickens included a line selected for ability to cause a high percentage of spontaneous regression of tumors, a susceptible line with a very low level of regression of tumors, and the two reciprocal crosses between these lines. Treatment with BCG greatly enhanced the percentage of regression in the line selected for regression and in the two reciprocal crosses, but was ineffective in the low regression line. Bursectomy of chicks from the low regression line did not permit BCG treatment to increase regression of Rous sarcomas.