Erythroid colonies derived from fetal blood display different growth patterns from those derived from adult marrow.

Fetal blood may be useful for the study of hematopoietic development in humans. However, the methods used to study blood cell colonies in adults may not be optimal for the study of colonies derived from fetal blood. Using cord blood from six healthy term pregnancies and marrow from six healthy adult volunteers, we compared the chronology of emergence, morphology, and differentiation of progenitor cell colonies from the two sources. In cultures of adult marrow, erythroid colony-forming unit colonies reached maximal concentrations after 8.5 +/- 0.3 days of culture (mean +/- SEM), but erythroid colony-forming unit colonies derived from fetal blood reached maximal concentrations sooner, after 6.5 +/- 0.2 days (p less than 0.01). Single-centered-erythroid burst-forming unit colonies from adult marrow (45 +/- 5/10(5) light-density, "accessory-cell"-depleted cells) reached a peak at 14 days, but from cord blood they were significantly greater at 9 days (200 +/- 15/10(5) cells) than at 14 days. When studying fetal blood erythroid colony-forming unit and "mature-erythroid burst-forming unit," colonies should be enumerated earlier than when studying adult marrow-derived progenitors. Otherwise, the concentrations of these progenitors will be significantly underestimated.