Medical Definition of Neutrophil. Neutrophil: A type of white blood cell, a granulocyte that is filled with microscopic granules, little sacs containing enzymes that digest microorganisms. Also known as polymorphonuclear leukocyte or poly.
Definition of Neutropenia. Neutropenia: Not enough neutrophils, neutrophils being a type of white blood cell (specifically a form of granulocyte) filled with neutrally-staining granules, tiny sacs of enzymes that help the cell to kill and digest microorganisms it has engulfed by phagocytosis.
Neutropenia occurs when the level of certain white blood cells in the blood drops below normal. The main role of white blood cells is to defend your child's body against harmful agents, like viruses or bacteria that can cause infection. There are many types of white blood cells. One type is called a neutrophil. This type surrounds and destroys harmful bacteria. Neutropenia occurs when the level of neutrophils is low. This can happen if: 1  The body does not make enough neutrophils. 2  Neutrophils are destroyed after they are made. 3  Neutrophils collect in a certain spot in the body instead of moving through the bloodstream.