Neutrophil production in the BM under homeostatic conditions. The neutrophil committed compartment in BM consists of dividing progenitors (mitotic pool: promyelocytes and myelocytes) and maturing nondividing progenitors (postmitotic pool: metamyelocytes, banded cells, mature cells, and hypersegmented neutrophils). The postmitotic transfer time is 5 to 6 days.^51-53 The origin of functional neutrophil phenotypes is uncertain, but they might be evoked by tissue instructions⁸¹ or parallel differentiation⁷⁴ or transdifferentiation.^79,80