Inhibition of granulopoiesis in diffusion chambers by a granulocyte chalone.

Granulocyte chalone obtained from media conditioned by rat granulocytes was tested on normal and vinblastine treated regenerating mouse marrow placed in an in vivo diffusion chamber culture system. Raw granulocyte chalone when injected several times during the early phase of culture significantly altered the cellular growth pattern as well as the parent-progeny relationships of both normal and regenerating marrow established within the chamber milieu. The total number of chamber cells (granulocytes plus macrophages) produced per inoculated stem cell was reduced by approximately 30 percent due to the action of granulocyte chalone. The reduction of granulocyte progeny may be the result of chalone acting during the early phase of culture to reduce the active growth fraction of granulocyte progenitor cells and thereby diminishing the amplification potential inherent in the initial cell inoculum.