Ultrastructure of fibrillar granules in human neutrophils.

Fibrillar granules (FGs) represent neutrophilic primary granules containing clustered filaments. We investigated neutrophils in the bone marrow obtained from 17 patients with chronic myeloproliferative disorders (CMPD) by electron microscopy. FG-positive neutrophils were seen in 15 of the 17 CMPDs with varying frequencies. The diameter of FG-filaments was 7-8 nm, showing that they corresponded to neither intermediate filaments nor actin filaments. (C) 1994 Wlley-Liss, Inc.