Figure 1.
Granulopoiesis. In the process of granulopoiesis, neutrophils develop stepwise from granulocyte-monocyte progenitor cells (GMPs). Each stage has a unique phenotype that is comprised of both morphologic features and cell surface markers. In the first step, the cell transitions into the myeloblast stage. The promyelocyte stage is characterized by the appearance of azurophilic granules. Specific granules start to develop at the myelocyte stage, and are fully present at the metamyelocyte stage; this is also the point at which the cell loses its proliferative capacity. After the metamyelocyte stage, the cell can be called a neutrophil; it acquires the distinctive banded nucleus and develops gelatinase granules and secretory vesicles.2 The arrows indicate the stage of the cell lines that are discussed in this paper.