Cellular origins of the fetal-haemoglobin-containing cells of normal adults

The origin of the small population of adult red cells which contain Hb F (F-cells) has been studied in a clonal disorder of haemopoiesis, polycythaemia rubra vera (P.R.V.). In eleven patients who had not received cytotoxic therapy F-cells comprised less than 0.1% to 11.9% of the circulating red cells, compared with 0.34% to 4.6% in 21 haematologically normal controls. Two additional patients were glucose-6-phosphate-dehydrogenase heterozygotes in whom the clonal nature of the P.R.V. could be demonstrated directly; they had F-cell values of 2.1% and 8.3%. These observations indicate that F-cells arise from the same population of stem cells as other adult cells and not from a separate stem-cell pool.