three cell differential count for WBC - White cells are separated by sizes: large cells are neutrophils and are also known as polymorphonuclear neutrophils (PMNs) [stabs, bands are immature cells, segs are the more mature cells], middle cells are eosinophils, atypical lymphocytes, and monocytes, small cells are lymphocytes. 40-76% of the white blood cells are PMNs. If one of the three cell populations is abnormal in number, then a microscopic differential is obtained. A predominance of immature cells (identified by 1-2 lobulation of the white cell nucleus) is called a shift to the left. A predominance of cells with 4 nuclear lobes is called a shift to the right. A left shift is present in the complete blood count when more than the total PMN count (segs plus bands) is >80% of the total white count. This is seen in bacterial infection, hemorrhage, and toxemia. A right shift is seen in patients with liver disease, megaloblastic anemia, and iron deficiency anemia.