Mast cell structure on electron microscopy

Micrograph A shows a mast cell from human lung tissue in which there are granules containing scroll-like structures. It is unclear precisely what these structures are composed of, although the granules contain predominantly tryptase. A higher power image of these scroll-like structures (yellow arrows) is shown in micrograph C. The black arrows point to granules with an amorphous structure, which likely represent developing (as opposed to mature) granules.
Micrograph B shows a mast cell from the skin with granules that display a lattice-like grating pattern on electron microscopy. The granules in this type of mast cell contain carboxypeptidase A, chymase, and tryptase. A higher power image of these granules (yellow arrows) is shown in micrograph D.