Urinary colony stimulating activity (CSA) has been studied in a 70-yr-old female with chronic cyclic neutropenia of unknown cause. Changes in urinary CSA were correlated with absolute granulocyte counts and were found to be highest when the granulocyte count was high or falling. It is suggested, on the basis of this and other data, that granulopoiesis, at least in part, may be regulated by a positive feedback control mechanism.

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© 1973 by American Society of Hematology, Inc.
1973
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