Eosinophils

Eosinophils are white blood cells thought to be important chiefly in defense against parasitic infections; they are activated by the lymphocytes of the adaptive immune response. The level of eosinophils in the blood is normally quite low. It can increase markedly in several situations, such as atopy, resulting in eosinophilia, an abnormally large number of eosinophils in the blood.