Mast‐cell precursors in various haematopoietic colonies of mice produced in vivo and in vitro

Abstract

Summary. We have examined mast‐cell precursors in various in vivo and in vitro haematopoietic colonies of mice. Cells from haematopoietic colonies of (WB x C57BL/6)F₁‐ +/+ mouse origin were injected into the skin of the congeneic W/W^v mice which are genetically depleted of tissue mast cells. The appearance of mast‐cell clusters at the injection site indicated the presence of mast‐cell precursors in the injected cell suspension. More than 40% of 12 d exogenous spleen colonies and 14 d in vitro mixed colonies contained mast‐cell precursors, but only a small proportion of 7 d exogenous spleen colonies, 9 d in vitro erythroid bursts or 14 d large in vitro neutrophil‐macrophage colonies contained mast‐cell precursors. Neither transient endogenous erythroid spleen colonies examined at the fifth day nor 7 d in vitro neutrophil‐macrophage colonies contained mast‐cell precursors. Among 12 d spleen colonies mast‐cell precursors were more frequent in the predominantly neutrophil than the predominantly erythroid colonies but 14 d in vitro mixed colonies, in which erythroid cells were predominant, contained mast‐cell precursors more frequently than 14 d in vitro neutrophil‐macrophage colonies. Therefore, differentiation of mast cells seems to be independent of either the neutrophil‐macrophage or erythroid cell lineages.