Final answer:
An eosinophil is a cell that releases granules containing cationic proteins toxic to parasites. Eosinophils are non-phagocytic leukocytes that specialize in defending against parasites by secreting highly toxic substances to kill them.
Step-by-step explanation:
The cell that releases granules containing cationic proteins toxic to parasites is an Eosinophil. Eosinophils are non-phagocytic leukocytes that specialize in defending against parasites. They contain granules and carry a bilobed earmuff-shaped nucleus. When activated, eosinophils secrete highly toxic substances to kill parasites. Basophils, neutrophils, and monocytes are other types of leukocytes, but eosinophils specifically release granules toxic to parasites.