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The sea urchin complement homologue, SpC3, functions as an opsonin
Lori A Clow1, David A Raftos, Paul S Gross
1Graduate Program in Genetics, Institute of Biomedical Sciences, George Washington University, Washington DC, USA.
The Journal of Experimental Biology
|May 15, 2004
Summary
The purple sea urchin
Area of Science:
- Marine Biology
- Immunology
- Invertebrate Zoology
Background:
- The purple sea urchin, Strongylocentrotus purpuratus, possesses a complement component C3 homologue (SpC3).
- SpC3 functions as a humoral opsonin in the sea urchin's coelomic fluid.
Purpose of the Study:
- To investigate the role of SpC3 in the immune response of Strongylocentrotus purpuratus.
- To determine if SpC3 enhances phagocytosis of target cells.
Main Methods:
- Opsonization of yeast target cells with coelomic fluid containing SpC3.
- Detection of SpC3 on opsonized yeast using an anti-SpC3 antibody.
- Confocal microscopy to visualize phagocytosis by coelomocytes.
Main Results:
- Incubation with SpC3 significantly increased the phagocytic activity against yeast cells.
- SpC3 was detected on the surface of opsonized yeast.
- Phagocytic activity was inhibited by an anti-SpC3 antibody, confirming SpC3's role.
- Polygonal phagocytes were identified as the primary cell type responsible for ingesting SpC3-opsonized yeast.
Conclusions:
- SpC3 acts as a major humoral opsonin in purple sea urchin coelomic fluid.
- SpC3 promotes phagocytosis by tagging target cells for ingestion.
- SpC3 receptors on polygonal phagocytes mediate the uptake of opsonized targets.