Ultrastructural evidence for the origin of mast cells in normal human bone marrow

Whether the origin of the progenitor of mast cells occurs in the basophil/mast cell system or the myeloid cell system of neutrophils and monocytes/macrophages remains controversial. Lactoferrin or lysozyme is known to be present in the myeloid cell system. By electron microscopy, antibodies against lactoferrin and lysozyme were observed to stain the granules of normal bone marrow mast cells. This supports the proposal that the precursor cell of bone marrow mast cells is nearer to the myeloid cell system than the basophil/mast cell system.