granulopoieesiin

Granulopoiesis is the physiological process by which granulocytes—neutrophils, eosinophils, basophils, and, in some contexts, mast cells—are produced from hematopoietic stem cells in the bone marrow. The process begins with multilineage hematopoietic stem cells that differentiate into common myeloid progenitors. These progenitors then give rise to granulocyte-macrophage progenitors, which further commit to granulocyte-primed progenitors. The committed precursors undergo a series of mitotic divisions, during which they acquire specific surface markers and functional characteristics that define each granulocyte lineage.

Key regulatory signals include cytokines and growth factors such as granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin‑3 (IL‑3), and interleukin‑5 (IL‑5). G-CSF, in particular, promotes the proliferation, differentiation, and mobilization of neutrophil precursors. Transcription factors like C/EBPα, PU.1, and GATA‑2 coordinate lineage commitment and maturation by regulating gene expression.

During maturation, precursors undergo shape changes, chromatin condensation, and cytoplasmic granule formation. Mature granulocytes enter the bloodstream as non‑activated cells and acquire full functional competence upon encountering inflammatory signals. The rate of granulopoiesis is tightly controlled to maintain an appropriate circulating pool of granulocytes for host defense while preventing excessive neutrophilia or tissue damage. Dysregulation of granulopoiesis can lead to conditions such as neutropenia, chronic myelogenous leukemia, or autoimmune disorders, underscoring its clinical relevance.