Abstract
The survival of lethally X-irradiated (BALB/c X A) F1 hybrid mice was greatly prolonged by the injection of leukemoid blood from (BALB/c X C3H) F1 hybrid mice. The luekemoid reaction was induced by the subcutaneous growth of the squamous-cell carcinoma A 280. Quantitative estimates indicate that many and perhaps all of the cells in the lymph nodes or marrow of the irradiated protected mice were derived from the leukemoid blood.