Effects of Short- and Long-Term Ultraviolet B Irradiation on the Immune System of the Common Carp (Cyprinus carpio)

Abstract

Carp (Cyprinus carpio) were repeatedly exposed to 0, 60, 120 and 240 mJ/cm2 ultraviolet B (UVB) radiation three times in 1 week (short-term exposure) or 12 times in 4 weeks (long-term exposure). The effect of UVB on the functioning of the carp immune system was studied on day 2 after the final irradiation. After short-term UVB exposure, the whole-blood respiratory burst and cytotoxic activity were markedly enhanced, with parallel responses in both the number of circulating granulocytes and in the plasma cortisol concentration of the fish. These changes were not detectable after long-term exposure. The respiratory burst by head kidney granulocytes was suppressed dose dependently after both exposures, but cytotoxic activity was not affected. Exposure to UVB also modulated lymphocyte functions: nonstimulated and PHA-stimulated proliferation of head kidney lymphocytes in vitro was enhanced by both short-term and long-term exposure. LPS-stimulated proliferation was not affected by exposure nor was the number of immunoglobulin-secreting cells in the head kidney. In long-term exposure, the highest dose reduced the level of plasma IgM. This study indicates that UVB irradiation induces immunomodulation in the blood and head kidney of the carp and that the effects of short- and long-term exposure differ from each other. The results emphasize the potentially harmful impact of increased solar UVB radiation on fish immune functions.

Ultraviolet B Irradiation Affects Resistance of Rainbow Trout (Oncorhynchus mykiss) Against Bacterium Yersinia ruckeri and Trematode Diplostomum spathaceum

“…UVB‐exposure of six consecutive days enhanced the immunological potential in the blood of uninfected rainbow trout by increasing the number of circulating granulocytes. Also in an earlier study, UVB‐induced increase in the percentage of carp blood granulocytes was found after 1 week irradiation, but thereafter the cell numbers returned to normal level despite the ongoing exposure of fish (5). Phagocytic macrophages and neutrophils play a major role in clearing the pathogens from the intraperitoneal cavity after an intraperitoneal injection of bacteria into fish (44), and the lower number of Y. ruckeri in the tissues of UVB‐exposed rainbow trout after 1 week irradiation (2 days p.i.)…”

“…UVB‐induced immunomodulation is suggested to be transmitted partly via the cortisol‐mediated stress response, as increased plasma cortisol concentration and blood granulophilia are often detected in irradiated fish (3,5). In this work, exposure of fish to UV‐depleted radiation was used to distinguish the effects of UVB‐treatment from those possibly caused by visually perceived changes in illumination when the lamps are turned on for irradiation.…”

“…One of the harmful effects of excess UVB‐exposure is the compromised functioning of the immune system, which may lead to increased susceptibility to diseases. UVB‐induced immunomodulation has been described in cyprinid fish, roach ( Rutilus rutilus ) (1–4) and common carp ( Cyprinus carpio ) (5,6), and recently also in rainbow trout ( Oncorhynchus mykiss ) (6). Irradiation affects both specific and nonspecific branches of fish immune system, including modulations in the functioning of phagocytes, natural cytotoxic cells as well as lymphocytes (1–6).…”

Possible reasons for late summer brown trout (Salmo trutta Linnaeus 1758) mortality in Austrian prealpine river systems

“…The influence of UV and of temperature on the immune system of teleost fishes has been documented in several studies (Salo et al., 2000a,b; Markkula et al., 2005a,b, 2006). UV radiation can suppress natural cytotoxic cell activity in head kidney and blood, in the production of antimicrobial oxygen radicals by the head kidney phagocytes, increase the numbers of circulating granulocytes, decrease the numbers of lymphocytes (Salo et al., 2000a,b), and reduce the resistance of fish to bacteria and parasites (Markkula et al., 2005b).…”

“…(2005) demonstrated that environmental pollutants passing through sewage plants could affect the immune system of fish, exposing brown trout to diluted sewage plant effluent; (2) Bacterial or viral diseases could cause immune deficiency as well as mortality, thus brown trout were exposed to UV‐disinfected pathogen‐free river water. Fish were also examined for ectoparasites, common fish diseases and proliferative kidney disease; (3) Sub‐optimal temperatures and drastic temperature changes can be stressors causing immune deficiency and mortality (Bly and Clem, 1992; Le Morvan et al., 1998), similar to extensive solar UV radiation (Salo et al., 2000a,b; Markkula et al., 2005a,b). S. trutta were therefore exposed to river water under natural light and darkness, and the temperature and UV radiation monitored.…”