抄録
Eosinophilic granular cells (EGCs) of fish are the granulocytes existing in the tissue. Their morphological characteristics have led to suggestion that fish EGCs are analogous to mammalian mast cells. It has been postulated that EGCs are involved in defense mechanisms, with EGCs degranulating after injection of non-self materials. The aim of this study is to determine the role of tilapia EGCs in inflammatory responses.
Neutrophil migration was observed after the degranulation of tilapia EGCs. Substance P (neurotransmitter) or anaphylatoxins (C 3 a and C 5 a) induced the EGCs degranulation. In the in vitro experiments, supematants of the degranulated EGCs induced neutrophil migration, indicating neutrophil migration-stimulating factor (s) were released after the degranulation of tilapia EGCs.
Injection with tilapia EGC lysates enhanced the vascular permeability, and the lysates induced the Ca2+ uptake by cultured tilapia vascular endothelial cells. These results indicate that tilapia EGC products directly activate the endothelial cells and increase the vascular permeability. The EGC products also induced expression of the neutrophil adhesion molecules by cultured vascular endothelial cells, because neutrophil adhesion to the endothelial cells increased after stimulating the endothelial cells with the EGC lysates.
These functions and properties of tilapia EGCs are resembled to those of mammalian mast cells, and EGCs of tilapia appear to be homologous to mammalian mast cells.
