The origin and role of blood-borne monocytes in rats with a transplanted myelogenous leukaemia.

The growth of a transplantable myeloid leukaemia into its syngeneic host is accompanied by a progressive increase in the number of blood monocytes. These were shown to be of host origin and were not derived from the inoculated leukaemia cells. The host response which is responsible for the monocytosis differs from that associated with the entry of monocytes into immunogenic sarcomas.