Erythropoiesis from adult but not fetal blood-derived CD133+ stem cells depends strongly on interleukin-3.

We have shown previously that erythropoiesis in cultures from fetal blood depends less on interleukin-3 (IL3) than erythropoiesis from adult blood. This paper explores if this is due to different proportions of stem cell sub-populations with different IL3 requirement, or to different IL3 requirement on fetal and adult stem cells in general. The CD133 (AC133) antigen is found on half of all CD34+ cells with erythropoietic potential and is thought to mark a primitive stem cell sub-population. This work compares the IL3 requirements of CD133+ and CD133-CD34+ cells derived from fetal (12-20 weeks) and adult blood. Erythropoiesis was monitored using flow cytometry and colony counting. Erythropoiesis from adult CD133+ but not CD133-CD34+ cells was dramatically delayed (6-8 days) in the absence of IL3. In cultures from fetal blood, both CD133+ and CD133-CD34+ cells showed only a small dependency on IL3. The ratio of erythroid colony-forming CD133+ cells to erythroid colony-forming CD34+ cells was 0.5-0.6 in adult and 0.2-0.4 in fetal blood. The differential IL3 dependency of erythropoiesis from fetal and adult blood CD133+ and CD133-CD34+ stem cells may be relevant for the choice and preparation of stem cells for clinical purposes.