Figure 5.

Representative examples of colony types in CFU assays. Human fetal liver cells were subjected to colony forming unit (CFU) assays that included a complete set of hematopoietic growth factors in a methylcellulose medium. Four different types of colonies could be identified and counted in light microscopy. (a) Small CFU-E colony that derives from a more mature erythroid progenitor; (b) large BFU-E colony that originates from an immature erythrocyte progenitor; (c) CFU-GM colony that originates from a primitive granulopoietic progenitor and does not contain erythrocytes; (d) CFU-GEMM colony that derives from the most primitive hematopoietic progenitor, forming very large colonies containing all four lineages.