Immune response of eel against fish pathogen, Edwardsiella tarda

어류 병원성 세균 Edwardsiella 에 대한 뱀장어의 면역 반응

To study the immune responses of the japanese eel. Anguilla japonica, fish were injected intraperitoneally with several types of Edwardsiella tarda antigen, i. e., FKC(formalin killed cells), HKC(heat killed cells) or LPS(lipopolysaccharide), and the changes of immunocytes numbers, phagocytosis and agglutination titre in the peripheral blood of the fish were investigated. The number of lymphocytes in the peripheral blood of eels were decreased until 6 hours after injection, and then were turn to normal levels after 24 hours of injection. However, the level were slightly increased and were remained after 24 hours. The number of neutrophils of FKC, HKC or LPS injected fish were the highest at 12 hours after injection and were decreased slowly after that. Three weeks after the injections, the agglutination of antibody titre of all immunized groups were reached at 128 and were remained this level thereafter. However 6 weeks after the injections, that in HKC injected fish were dropped the level up to 4. Fish were injected with LPS and the blood from the fish were bled after 12 hours. Then the blood were incubated with E. tarda. Six hours after incubation, the phagocytic index was reached the highest level, 28.3. One week after the LPS injection, the blood were again bled and incubated with E. tarda. The phagocytic index at this time was 3.9. The phagocytic indexes of the fish injected with FKC and HKC, treted as same LPS injected fish as above, were 18.8 and 10.7, respectively. The phagocytic index of the control fish was 1.2. The antibacterial activities of normal antiserum against E. tarda were shown for both FKC and LPS injected fish, but not for HKC injected fish. The RPS(relative percentage of survival) of HKC, FKC and LPS injected fish in the challenge test were 10%, 20% and 30%, respectively. These results suggest that the effect of protection of the eel which were injected with antigen were varied with the method of preparation of the antigen.

뱀장어의 복강내에 Edwardsiella tarda의 FKC, HKC 및 crude LPS를 주사한 후 경시적으로 순환혈액 중 면역세포 수의 변화와 식작용, 항체가를 비교하여 항원 종류별 뱀장어의 면역 반응을 검토하였다. 백신 투여 뱀장어의 순환혈액 중 림프구 수는 백신 투여 후 6시간까지 감소하였으나 이후 증가하기 시작하여 24시간 후에는 정상치로 회복되었다. 이후 모든 면역 실험구에서는 실험기간 동안 대조구에 비하여 림프구 수가 증가된 상태로 지속되는 경향을 보였다. 한편, 호중구의 출현수를 대조구와 비교하면 백신 투여 후 12시간 이내에 최고치를 나타낸 후 서서히 정상 수준으로 회복되는 경향을 나타내었다. 모든 백신 투여 실험구의 혈청중 항체가는 백신 투여 3주째에 128에 이르러 높은 항체가가 지속되었으나, HKC 면역구의 경우에는 6주후 4로 떨어졌다. 호중구의 식작용에 있어서는 LPS 면역구의 항원 주사 6시간 후와 1주후의 반응 6시간째의 식균지수가 각각 28.3과 3.9로 가장 높았다. 항원 주사 후 12시간째의 식균지수가 반응 6시간째 FKC 면역구 18.8, HKC 면역구 10.7, LPS 면역구 28.3 및 대조구 1.2로서, 1 주 후 각 면역구의 식균지수보다 높게 나타났다. 신선 항혈청의 항균작용은 FKC와 LPS 투여구에서만 나타나고, HKC 투여구에서는 세균 수의 감소를 볼 수 없었다. 그리고, 공격시험에서는 HKC, FKC 및 LPS 면역구의 RPS가 각각 10%, 20% 및 30% 이었으므로, 본 세균은 항원의 처리 방법에 따라 숙주의 방어력 증강에 미치는 효과가 다른 것을 알 수 있었다.