MC are derived from hematopoietic stem cells in the BM. A committed, small, agranular progenitor (MCp) has been identified in the human vasculature that requires IL-3 for its survival and initial differentiation. In the presence of IL-3 (and IL-6), isolated MCp can be driven to further differentiate into an intermediate form termed a pre-MC. These latter cells can be further driven to a more mature state by culture with SCF, characterized by more mature SG and expressing a surface phenotype similar to MC isolated from human tissue. We have limited the phenotypic markers to the data presented in the article by Dahlin et al but assume that maturation changes for SG would be progressive, whereas β7 integrin (β7) expression declines. Professional illustration by Somersault18:24.