The trapping of intravenously injected extracellular products fromAeromonas salmonicidain head kidney and spleen of vaccinated and nonvaccinated Atlantic salmon,Salmo salarL.

Trapping of intravenously injected crude extracellular products fromAeromonas salmonicidawas studied in Atlantic salmon,Salmo salarL. Frozen tissue from head kidney and spleen was collected 1 h and 8 h after the injection and localisation ofA. salmonicidaantigens, complement factor 3 and immunoglobulin was investigated in vaccinated and nonvaccinated fish using a double immunofluorescence staining technique. In the head kidney of vaccinated fish,A. salmonicidaantigens was colocalised with complement factor 3 and immunoglobulin in sinusoidal cells. A weaker reactivity toA. salmonicidaantigens was detected in colocalisation with complement factor 3 alone in nonvaccinated fish. In the spleen, ellipsoidal sheaths showed reactivity toA. salmonicidaantigens in fish from both groups. In addition, the ellipsoids that trappedA. salmonicidaantigens were stained for complement factor 3 and immunoglobulin in the vaccinated fish but stained for complement factor 3 alone in nonvaccinated fish. Computer-assisted morphometric analysis was further used to provide semi-quantitative estimates ofA. salmonicidaantigens and complement factor 3 in the head kidney. The estimated stained areas were significantly larger for the two antigens in vaccinated fish compared with nonvaccinated fish.