|Budget Amount *help
¥6,900,000 (Direct Cost : ¥6,900,000)
Fiscal Year 1997 : ¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1996 : ¥4,500,000 (Direct Cost : ¥4,500,000)
To develop rapid evaluation methods of immunopotentiators in fish, the mechanism of the immunopotentiation in carp was analyzed using a fungi-derived beta-1,3-glucan and sodium alginate prepared from a brown algae as model materials of immunopotentiators. The beta-1,3-glucan activated the complement of carp and intraperitoneal administration of the beta-1,3-glucan elevated the expression level of mammalian CR3-like complement receptors on head kidney phagocytes. Therefore, the enhancement of phagocytic activity of the phagocytes which is endowed by the increase in complement receptors expression probably plays an important role in elevation of host defense against bacterial infection. On the basis of these findings, we have isolated carp C3a fragment, which would be a good indicator for complement activation, and developed the a detection method of carp C3a as well as a rosette assay of the receptors. On the other hand, neither activation of complement nor enhancement of phagocyte activity was observed after intraperitoneally injected sodium alginate. Rather, sodium alginate induced a great migration of head kidney leukocytes to the peritoneal cavity, indicating that sodium alginate stimulate the release of chemotactic cytokines from resident leukocytes in the cavity. These results show that there are distinct mechanisms underlying the enhancing effects of those polysaccharide immunopotentiators on the fish host defense system. Functional and immunochemical assays of cytokines are not applicable to fish, because few data has been accumulated on fish cytokines. However, analysis of gene-expression, which is specifically stimulated by the administration of immunopotentiator, will help to overcome the difficulties.