Phagocytosis

Definition

A form of endocytosis in which a cell engulfs large particles (typically >0.5 μm), such as microorganisms, cellular debris, or foreign material, by extending its plasma membrane around the target and internalizing it within a membrane-bound vesicle called a phagosome. In arthropods, phagocytosis is a primary defense mechanism executed by circulating hemocytes (especially plasmatocytes and granulocytes) that recognize and destroy invading bacteria, fungi, and parasitoid eggs.

Etymology

Greek phagein (to eat) + kytos (cell) + -osis (process)

Example

When a parasitoid wasp oviposits into a lepidopteran larva, the host's hemocytes attempt to encapsulate the foreign egg through phagocytosis and subsequent melanization; some parasitoids have evolved virus-like particles to suppress this cellular immune response.

Synonyms

• cellular eating

Related Terms

• hemocyte
• phagosome
• endocytosis
• Encapsulation
• melanization
• innate immunity
• Plasmatocyte
• Granulocyte

Usage Notes

Distinguished from pinocytosis (cell drinking), which internalizes fluid and dissolved solutes. In insect immunology, phagocytosis typically targets small pathogens and particles, while larger targets trigger encapsulation—a cooperative, multicellular defense. The term applies broadly across eukaryotes but is most frequently discussed in medical entomology and invertebrate pathology contexts concerning vector competence and host–parasite interactions.