An Investigation into the Development and Fate of Neutrophil Giant Metamyelocytes using the Techniques of Electron Microscopy and High Resolution Autoradiography

The neutrophil giant metamyelocytes present in vitamin B12-and folate-deficient patients were studied using the techniques of electron microscopy and electron microscope autoradiography. The ultrastructural features of the cytoplasm of a proportion of these cells resembled those of promyelocytes and myelocytes, particularly with respect to the types of neutrophil granules present. This finding suggests that the giant metamyelocytes result from an abnormal type of development in promyelocytes and myelocytes which have been arrested or retarded in their progress through the cell cycle. The hypothesis that giant metamyelocytes eventually die within the marrow was supported by the observations that a significant proportion of these cells contain intracytoplasmic autophagic vacuoles, that some giant metamyelocytes suffer from a marked depression of RNA and protein synthesis and that degenerating giant metamyelocytes can be recognized within the cytoplasm of some bone marrow macrophages.