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.