(Basic structure of the cell-kinetic model of granulopoiesis). Major model compartments describing granulopoietic cell stages are S (pluripotent stem cells), CG (colony forming units of granulocytes and macrophages), PGB (proliferating granulopoietic blasts), MGB (maturing granulopoietic blasts - subdivided into metamyelocytes (G 4),banded granulocytes (G 5) and segmented granulocytes (G 6)) and GRA (circulating granulocytes). The system is regulated by feedback loops. A major loop is mediated by G-CSF which is produced endogenously but can also be applied subcutaneously. Chemotherapy (CX) induces acute cell loss. The model is essentially the same as in.