TF storage in eosinophil myelocytes. In thin sections of human bone marrow, TF is found to be expressed in intracellular compartments of leukocyte progenitor cells. The hematopoietic cells were visualized by immunoelectron microscopy, using a monoclonal anti-TF antibody and a secondary antibody coupled with gold particles. (A) Neutrophil metamyelocytes (recognized by their characteristic nuclear morphology and the dense heterochromatin) and (B) basophil myelocytes (identified by the morphology and size of their intracellular granules) contain TF in different types of granules. (C) In the eosinophil myelocytes, high amounts of TF are expressed in the coreless granules (identified by the presence of arginine-rich crystals in intracellular granules). The marked areas in the left-hand pictures are magnified on the right-hand side. Arrows indicate specific TF labeling.