Colony formation by canine hemopoietic cells in vitro. Inhibition by polymorphonuclear leukocytes.

In soft agar cultures of canine blood leukocytes, an inhibition of colony formation was observed relative to the size of the inoculum. Analysis of the cellular composition of the inoculum suggested that this inhibition was associated with the number of polymorphonuclear leukocytes present. Removal of phagocytic cells by the iron ingestion method or selective destruction of granulocytes by freezing in the presence of dimethyl sulfoxide eliminated the inhibitory action on colony formation. In mixed cultures of canine bone marrow and antologous blood leukocytes, a similar inhibition of colony formation was observed. The results presented indicate that polymorphonuclear leukocytes, if present in a concentration exceeding 2.5X10(6)/ml of inoculum, inhibit in vitro granulocytic/monocytic colony formation.