Effects of ultraviolet radiation on the immune system of fish

There is a widespread concern over the increasing amounts of ultraviolet radiation reaching the earth due to stratospheric ozone depletion. Ozone depletion was first recognised as a problem in the middle of the 1980s and is estimated to continue until 2050. Ultraviolet radiation has harmful effects on human and animal health, including suppression of the immune system. Since ultraviolet radiation penetrates into water it has negative effects in fish species as well. Adult roach, Rutilus rutilus cyprinidae, were exposed to a single dose of either ultraviolet A (UVA; 3.6 J/cm² ) or ultraviolet B (UVB; 0.5 J/cm² ) irradiation in order to study the effects of ultraviolet radiation on the immune defence of fish. A panel of immune parameters were assayed during a 14-day follow-up. Exposure to either UV A or UVB irradiation suppressed mitogen-stimulated proliferation of blood and splenic lymphocytes, but the production of antibodies was not affected. The activity of natural cytotoxic cells was suppressed following both types of irradiation. UVB, but not UVA, suppressed transiently the migration and respiratory burst of head kidney phagocytes. UVB exposure induced marked granulocytosis and lymphocytopenia in the blood and raised the plasma cortisol concentration, which suggests that stress induced by UVB is involved in the modulation of immune parameters. These results imply that both UVA and UVB have the potential to suppress nonspecific as well as specific aspects of the immune defence of fish.