Phagocytes

Definition

Immune cells that engulf and digest foreign particles, pathogens, cellular debris, or apoptotic cells through the process of phagocytosis. In arthropods, phagocytic hemocytes are the primary cellular defense against bacterial, fungal, and parasitic infections, circulating in the hemolymph or residing in fixed tissues such as the fat body or pericardial cells. These cells recognize pathogen-associated molecular patterns, form phagosomes around targets, and destroy ingested material through enzymatic degradation and oxidative burst.

Etymology

From Greek phagein (to eat, devour) + -kutos (hollow vessel, cell)

Example

In mosquitoes, granulocytes and plasmatocytes are the principal phagocytic hemocyte types that engulf malaria parasites (Plasmodium) during their ookinete stage in the midgut, representing a critical barrier to vector competence and disease transmission.

Synonyms

• phagocytic cells
• scavenger cells

Related Terms

• Phagocytosis
• Hemocytes
• macrophages
• neutrophils
• immune response
• pathogen-associated molecular patterns
• melanization
• nodulation

Usage Notes

Distinguish from pinocytosis (cell drinking) and other forms of endocytosis. In insect immunology, phagocyte function is often studied alongside humoral defenses (antimicrobial peptides, phenoloxidase cascade). The term is sometimes used more broadly to include any cell capable of phagocytosis, but specialists may reserve it for professional phagocytes with dedicated immune roles. Arthropod phagocytes lack the antibody-mediated opsonization seen in vertebrates, relying instead on lectins, thioester-containing proteins, and other pattern-recognition molecules.