Behavior of p388 mouse leukemia in the chick embryo and hatched chick

P388 and several other mouse leukemias grow poorly on the chorio-allantoic membrane of the chick embryo, but may proliferate rapidly when introduced into the embryo by intravenous injection, or by metastasis from chorio-allantoic explants. Proliferation of P388 cells in the embryo probably continues until shortly after it has hatched, and then stops; however, viable leukemic cells may persist in the chick brain for as long as 6 weeks after hatching. The brain appears to be the most favorable site for growth and long-term survival of P388 cells. P388 cells injected intravenously or intracerebrally into 1-day-old hatched chicks will survive for long periods, but, when given to 7-day-old and older chicks, the cells fail to survive. This suggests the rapid maturation of immunological competence by the chick shortly after hatching. Marked splenomegaly and hematopoietic stimulation in the embryo may result from injection of P388 and several other mouse leukemias. The splenomegaly is due to proliferation of host cells, particularly the granulocytic elements. The significance of the increased hematopoiesis and splenomegaly and its relation to that reported after the transplantation of homologous adult spleen into the embryo require further study.