Investigations on the pool size, proliferative state and differentiation pattern of splenic CFUC in normal dogs.

In the present study we investigated the absolute numbers of granulocytic progenitor cells (CFUc) in the spleens of adult normal dogs, their differentiation pattern and also their proliferative state. Between 10 and 40 times as many CFUc were found in the spleens of individual dogs as were present in the total blood volume at the same time under physiological conditions. About 16% of the splenic CFUc were in the DNA synthetic phase. In spite of the presence of CFUc in the splenic tissue, there was a lack of morphologically identifiable granulocytic precursor cells and hence no extramedullary granulocyte production. The similarities between circulating CFUc and the splenic CFUc with respect to their differentiation pattern in vitro and their cell cycle state suggest that the CFUc that reside in the splenic tissue are identical to thea CFUc population in the circulation.