Defense mechanism of Japanese flounder [Paralichthys olivaceus] immunized with formalin-killed cells of Streptococcus iniae
2004
Kakuta, N. (Nagasaki Univ. (Japan). Faculty of Fisheries) | Kanai, K. | Tsukahara, J. | Ichinose, H. | Sasaki, H.
To study the defense mechanism of Japanese flounder Paralichthys olivaceus immunized with formalin-killed cells of Streptococcus iniae, changes in viable count of intravenously inoculated live cells of S. iniae were investigated. The majority of the bacterial cells were trapped in the kidney and spleen of both immunized and non-immunized flounder within 10 min postinoculation (pi). Then the viable counts in these organs of immunized fish increased by 24 h pi and thereafter decreased to the detection limit at 96 h pi. On the other hand, those of nonimmunized fish increased to the lethal level at 48 h pi. Viable counts of inoculated S. iniae in the organs of normal flounder preinjected with sera of immunized fish collected at 2 day pi of live bacteria decreased, suggesting the appearance of macrophage-activating factor(s) in the sera. Partial purification of the factor suggested the multiplicity of the factor, and one of the most active components was a high molecular weight substance exhibiting bacterial agglutination.
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