CAT and immune system toxicity: Intracellular ROS, MDA, and contents and reduced activity of antioxidant enzymes, such as SOD, GST, and CAT, are the main biomarkers of the cytotoxicity of ANTX-a to carp immunocytes in vitro, which were also measured to assess the influence of ANTX-a on fish lymphocytes and to investigate the potential mechanism of ANTX-a-induced immunotoxicity.