Eosinophil white blood cell. Transmission electron micrograph (TEM) of a section through an eosinophil white blood cell (leukocyte). Eosinophils circulate in blood and account for only 1-2 per cent of all white blood cells. An eosinophil only survives in blood for a few days but may persist for a week or more after migration from vessels into tissues. Their main functions are to modulate inflammatory reactions and to attack and neutralise foreign or non-self entities such as bacteria and parasites by releasing powerful proteins or enzymes that disable or destroy their targets. These secretory products are stored in the many cytoplasmic granules (dark spots). Magnification: x22,200, when printed 10 centimetres wide.