Immune-related genes expression profile in orange-spotted grouper during exposure to Cryptocaryon irritans

Cryptocaryon irritans is one of the most important ectoparasites of marine fish. To identify the potential role of immune-related genes in antiparasitic immune responses in fish, we monitored the expression change of IL-8, COX-2, C-type lectin and transferrin in local and systemic immune organs of orange-spotted grouper post-C. irritans infection. IL-8 expression was up-regulated during the course of infection in the skin, while COX-2 and transferrin expression was up-regulated in the gill. COX-2 expression was significantly down-regulated in the spleen (0.7-5% of its control) and head kidney (0.5-4% of its control) post-primary infection. Transferrin expression was also down-regulated in the spleen and head kidney from 6 h to 5 days post-primary infection. However, C-type lectin expression was up-regulated in all tested organs post-infection, with the exception of day 7 in the spleen post-primary infection where the expression level was slightly down-regulated (44% of its control). These results suggest that these four immune-related genes play an important role in grouper anti-C. irritans infection and that local immune organs as the active organs contribute more than systemic immune organs to this course.