THE EFFECTS OF GESTATION ON CIRCULATING PROGENITOR CELLS

The frequency of BFU-E in second-trimester fetal blood (484 +/- 104/10 (5)) falls progressively during gestation to a value of 69 +/- 41/10(5 ) in cord bloods of 36 weeks gestation and beyond, but this is still s ignificantly greater than adult blood values of 14 +/- 8 (P < 0.01). B FU-E obtained from unfractionated peripheral blood mononuclear cells f rom fetuses/neonates less than 36 weeks gestation were more sensitive to erythropoietin than adult BFU-E, but the sensitivity of highly puri fied BFU-E obtained from second-trimester fetal liver as similar to th at in adult cells. Almost maximal growth of BFU-E from purified fetal progenitor cells could be achieved with erythropoietin alone, whereas adult cells required the presence of other factors with 'burst-promoti ng activity'.