The phagocytosis of fish phagocytes and the surviving activity

• Main Authors: Yu, Chun-ming, 余俊明
• Other Authors: Lin Yung-Chang
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/64582812629394147799

碩士 === 國立中興大學 === 獸醫學系 === 86 === AbstractThe phagocytes are believed to play the major role in fish non-specific defense against most aquatic pathogens and irritants. In this study, the phagocytes of tilapia (Oreochromis nilotica) and rainbow trout (Oncorhynchus mykiss) isolated from blood, head kidney and spleen were used to compare the phagocytosis and eradication abilities against several aquatic pathogens such as Vibrio parahaemolyticus, V. anguillarum, V. vulificus, Aeromonas hydrophilia and Streptococcus spp. using flow cytometry analysis. In general, the blood phagocytes had better phagocytosis capability than spleen and head kidney phagocytes in engulfing the same pathogen. The results also demonstrated that bacteria opsonized with or without fish serum in advance did not influence most phagocytes to uptake and eradicate same bacteria after 120 minutes incubation, but tilapia spleen phagocytes could enhance their activity when bacteria opsonized with 1:256 fold diluted fish serum. In addition, the number of bacteria (V. parahaemolyticus) engulfed by tilapia spleen phagocytes would obviously decrease if bacteria were heat inactivated before interacting with phagocytes.Moreover, all phagocytes showed higher capability of phagocytosis against most toxigenic bacteria especially those could produce hemolysins and extracellular products (ECPs) to induce significant cytotoxicity of phagocytes. In order to characterize the influence of bacterial toxicity, bacteria were cultured in LB broth containing different concentration of 2,2'-dipyridyl to simulate the pathogens growing at iron- limiting condition while interacting with phagocytes in fish. The results showed both A. hydrophilia (A2) and V. anguillarum (Va2) apparently increased their hemolytic and cytotoxic efficiency against all phagocytes under iron starvation. Furthermore, the ECPs could induce granulation and size variation of phagocytes and affect their eradication ability. However, ECPs of A. hydrophilia (A2) did obviously enhance rainbow trout and tilapia head kidney phagocytes for uptaking other less or non-pathogenic bacteria. In contrast, ECPs of A. hydrophilia (A1), without any cellular cytotoxicity against phagocytes, showed no influence the capability of phagocytosis.