| Summary: | 碩士 === 國立中興大學 === 獸醫病理學研究所 === 89 === Abstract
Fish immunity is influenced significantly by the fluctuation of environmental temperature due to fish belong to the poikilothermic animals. It is generally accepted that higher temperatures would enhance the specific immune responses whereas lower temperatures adversely affect their expression. However, few data are available to explain the temperature effects on nonspecific defense mechanism in fish. The aim of this study is to evaluate the effect of low environmental temperature on phagocyte function and to estimate the antibody secreting cells (ASCs) after immunization in blue tilapia. The results demonstrated that phagocytic activity of blood, head kidney, and spleen cells against Streptococcus spp. showed decreasing when fish maintained at low environmental temperature (20±1°C) for one week by flow cytometry analysis. However, phagocytosis would enhance gradually and even higher than normal temperature (28±1°C) group after 3 weeks inoculation. On the other hand, the respiratory burst of phagocytes showed increasing during fish adaptation to low temperature on their bactericidal activities against streptococcus spp..
Moreover, exogenous antigen, recombinant Pasteurella multocida toxin (rPMT), was applied to identify the proliferation of ASCs in kidney and spleen after immunilization. At first, fish immunoglobulins (Ig) was purified from tilapia serum and used for preparation of mouse anti-fish Ig antibody. The purified Ig had a apparent molecular weight of 78 kDa (heavy chain) and 23 kDa (light chain) in SDS-PAGE. After fish were immunized with rPMT to elicit primary antibody response, the ASCs can be detected after one week post first immunization in both head kidney and spleen using ELISPOT assay. However, the specific antibody titer in the serum was still not detectable by ELISA except fish receiving the booster immunization. Furthermore, a significant lymphoproliferation was noticed on mononuclear cells that were isolated from head kidney when re-stimulated with rPMT antigen. It suggested the ELISPOT and lymphoproliferation assay are more sensitive than ELISA method for evaluation the specific immunity in fish.
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