Sideroblastic colonies in erythroid cultures grown from normal human marrow.

Normal human erythroid progenitor cells from bone marrow were grown in culture using a methyl cellulose clonal assay technique. Sideroblastic erythroid cells were found in the majority of colonies examined at 14-17 days, and a few sideroblasts were found in some of the colonies examined after shorter periods of culture. Electron microscopy confirmed the presence of both intramitochondrial iron deposits and cytoplasmic ferritin aggregates. These morphological appearances probably represent an abnormality induced by the in vitro culture conditions and cannot be used as evidence for an intrinsic defect in haem synthesis.