Growth kinetics of erythroid progenitor cells from cord blood. (A) Human erythroid progenitor cells from cord blood were grown in liquid culture in the presence of SCF, Epo, IGF-1, dexamethasone, and estrogen. Cumulative cell numbers (calculated per 10 mL cord blood) of three representative experiments determined in regular time intervals are shown. (B) Aliquots of the cultures shown in (A) were subjected to cytocentrifugation and staining with neutral benzidine and histological dyes and analyzed for the proportion of proerythroblasts (proerbl), polychromatic and orthochromatic erythroblasts (pchrom and ochrom erbl, respectively), erythrocytes (ery), granulocytes (gran), macrophages (mac), and lymphocytes (lymph). The starting cell population (day 0) consisted mainly of granulocytes, monocyte/macrophages, lymphocytes, and some blast-like progenitor cells. Only nucleated cells are evaluated at day 0. (C) Photographs of the cells shown in (A) and (B) after cytocentrifugation and histological staining.