Given that transferrin mRNA levels are significantly more abundant in postsmolts Atlantic salmon than in fish in the freshwater phase [29] and that transferrin expression is modulated in response to infections and iron availability [30, 31], we generated transferrin-knockout (TF-KO) Atlantic salmon phagocytes from SHK-1 cells [19] to assess their response to P. salmonis infection in vitro. The gene discussed is TF; the disease is infection.