Plasmatocyte

Definition

The predominant class of hemocyte (circulating blood cell) in insects, functionally analogous to vertebrate macrophages. Plasmatocytes are phagocytic cells that patrol the hemolymph, engulfing pathogens, apoptotic cells, and cellular debris; they also secrete extracellular matrix components during development and wound healing. In Drosophila melanogaster, they constitute approximately 95% of hemocytes in healthy individuals and arise from both sessile subepidermal pools and the larval lymph gland. Identifying markers include NimC1, Hemolectin, Eater, and Peroxidasin.

Etymology

From Greek plasma (something molded or formed) + kytos (hollow vessel, cell)

Example

When a Drosophila larva is wounded, plasmatocytes rapidly migrate to the injury site, where they phagocytose bacteria and secrete extracellular matrix proteins to initiate encapsulation and tissue repair.

Synonyms

• phagocytic hemocyte
• macrophage-like hemocyte

Related Terms

• hemocyte
• lamellocyte
• crystal cell
• Hemolymph
• Phagocytosis
• lymph gland
• sessile hemocyte pool
• Encapsulation
• innate immunity

Usage Notes

Plasmatocyte is sometimes used more broadly across arthropods, but functional properties vary; in crustaceans and some insects, the term may overlap with 'granular hemocyte.' Contrast with specialized hemocyte types: lamellocytes (flattened, involved in encapsulation of large parasites) and crystal cells (contain phenoloxidase for melanization). Plasmatocytes are distinguished from prohemocytes (undifferentiated precursors) by their active phagocytic capacity and marker expression.