Neutrophils circulate in the peripheral blood for approximately 12 hours. Following emigration into tissues, neutrophils live for about 2 days. If the emigration was in response to an inflammatory stimulus, the tissue life span can be greatly shortened. Removal of dead neutrophils is via the lymphatics, phagocytosis by macrophages, or by loss through mucosal barriers. The major inflammatory functions of neutrophils include phagocytosis and secretion of pro-inflammatory substances.
Neutrophils are the most active of the phagocytes and form the first line of cellular defense.
As a general rule, neutrophils are the predominant cell type in acute inflammation. Pro-inflammatory substances include lysosomal enzymes, products of oxygen metabolism, and products of arachidonic acid metabolism. Eosinophils These are about 15-20 um in diameter and have a segmented, usually bilobed nucleus. Eosinophils contain one prominent type of cytoplasmic granule which has a characteristic crystalloid core. Eosinophils are phagocytic, but much less so than neutrophils or macrophages, and are not usually considered as phagocytic cells.