Methylcellulose culture of human granulocytic progenitor cells (CFC *): results of bone marrow and blood cultures for normal subjects.

Normal values for the colony-forming ability of granulocytic progenitor cells (CFC) were established for 26 samples of normal bone marrow and 8 samples of normal blood cultured in methylcellulose. The concentration of CFC in the marrow was measured classically as the number of CFC per 10(5) nucleated marrow cells plated and, in addition, as the number of CFC per 10(5) precursors (myeloblasts, promyelocytes, and myelocytes) and per 10(5) metamyelocytes. A value approximating the total number of marrow CFC was calculated by using the number of CFC per 10(5) metamyelocytes. The normal value for circulating CFC were determined as number per ml of blood, per kg of body weight, per 10(5) circulating lymphocytes, and per 10(5) circulating granulocytes. The value of these different modes of expression are discussed. Although the values reported are not directly applicable from one laboratory to the next, they may constitute a useful reference point. Furthermore, they show that the statistical variation in the results is sufficiently small to permit the comparison of values found for pathologic samples with those determined for normal samples.