Harri M. Salo

Comparative effects of UVA and UVB irradiation on the immune system of fish.

Aquatic organisms can be harmed by the current levels of solar ultraviolet radiation. We have recently shown that exposure of fish to UVB irradiation alters the functioning of the fish immune system, but the effects of UVA radiation are unknown. The present study continues this work by characterizing UVA irradiation-induced immunological changes in fish. Roach, a cyprinid fish, were exposed to a single dose of either UVA (3.6 J/cm2) or UVB (0.5 J/cm2) irradiation. Both irradiations suppressed transiently mitogen-stimulated proliferation of blood lymphocytes. UVA, but not UVB, decreased hematocrit, plasma protein, and plasma immunoglobulin levels and increased the proportions of blood cells classified as unidentified leukocytes, possibly consisting of UVA-damaged lymphocytes. UVB, but not UVA, altered the functioning of head kidney and blood phagocytes, induced granulocytosis and lymphocytopenia in the blood and increased plasma cortisol concentration. These results imply that both UVA and UVB are potent modulators of the immune defence of fish.

Ultraviolet B Irradiation Modulates the Immune System of Fish (Rutilus rutilus, Cyprinidae) II: Blood

Abstract The effects of a single dose of ultraviolet B (UVB) radiation (0.4 J/cm2) on immunological functions by blood leukocytes and on hematological parameters was studied in roach (Rutilus rutilus), a teleostean fish. The respiratory burst of phorbol 12-myristate 13-acetate stimulated whole blood phagocytes increased significantly after UVB irradiation but spontaneous cytotoxicity of blood leukocytes toward 51chromium-labeled K562 target cells was not markedly altered. Differential cell counting revealed that UVB exposure significantly increased the proportion of granulocytes and significantly decreased the proportion of lymphocytes in the peripheral blood, whereas hematocrit and the total number of white and red blood cells were unchanged. Plasma cortisol concentration increased in UVB-exposed fish. Severe handling stress caused similar, although not as potent, effects on the measured parameters of fish blood as UVB irradiation. These observations suggest that in fish UVB brings about a stress response, which may account for the observed alterations in the immune parameters and leukocyte composition of blood. Exposure of fish to strong visible light induced no alterations in immunological or hematological parameters, making it unlikely that ultraviolet radiation mediates its effects through visual perception.

Effects of primary- and secondary-treated bleached kraft mill effluents on the immune system and physiological parameters of roach.

The present study was designed to examine, whether, effluents from a modern pulp and paper mill using elemental chlorine-free/total chlorine-free (ECF/TCF) bleaching, exert effects on the immune system of fish and, in addition, to relate these findings to physiological parameters known to be affected by bleached kraft-mill effluents (BKME). Roach (Rutilus rutilus) were exposed in laboratory conditions to primary- or secondary-treated effluent from a pulp and paper mill. In order to study their capability to respond to foreign antigens they were immunised with bovine gamma-globulin (BGG) prior to exposure. The number of anti-BGG antibody-secreting cells (ASC) and the number of immunoglobulin-secreting cells (ISC) in the spleen and blood as well as the level of anti-BGG specific antibodies and concentration of plasma immunoglobulin (IgM) were studied. Phagocytosis and migration of granulocytes of the head kidney were also determined. In addition to the immunological parameters, the activity of hepatic biotransformation enzymes, the carbohydrate metabolism and osmoregulation were examined. Exposure of roach for 21 days to BKME affected several immunological parameters. Both effluents, primary- and secondary-treated, impaired the immunoreactivity of the fish. Sex-related differences in the immune responses were evident in many parameters e.g. in the number of blood ISC and splenic ASC. Sex also had effects on cortisol levels and in the induction of 7-ethoxyresorufin O-deethylase (EROD). These results demonstrate that both primary- and secondary-treated effluent from a pulp and paper mill using ECF/TCF bleaching have effects on fish immune functions. Further, these findings suggest that steroids may contribute to immunomodulation in fish.

Exposure to Increased Ambient Ultraviolet B Radiation has Negative Effects on Growth, Condition and Immune Function of Juvenile Atlantic Salmon (Salmo salar)

Atlantic salmon (Salmo salar) parr were exposed in two outdoor experiments, ranging in duration from 52 to 137 days, to spectral treatments: (1) natural sunlight (=present ambient UVB level), (2) solar radiation supplemented with enhanced UVB radiation from lamps simulating 20% or 8% stratospheric ozone loss or (3) UVB‐depleted sunlight achieved by screening with Mylar‐D film. The growth, condition and immune function of the salmon were quantified after treatments. Exposure to enhanced UVB radiation retarded growth, and decreased hematocrit value and plasma protein concentration. Further, enhanced UVB radiation affected plasma immunoglobulin concentration. The results demonstrate that juvenile Atlantic salmon are not able to fully adapt to increased ambient UVB levels in long‐term exposures, and the interference with immune system function suggests a negative effect of UVB on disease resistance in Atlantic salmon.

Ultraviolet B Irradiation Modulates the Immune System of Fish (Rutilus rutilus, Cyprinidae) Part III: Lymphocytes¶

Abstract The effects of short-term exposure to ultraviolet B (UVB) radiation on lymphocyte-related parameters were studied under controlled laboratory conditions using roach (Rutilus rutilus), a cyprinid teleost, as the model fish. In vitro lymphoproliferative responses stimulated with a T-cell–specific mitogen, concanavalin A (ConA), or a B-cell–specific activator, lipopolysaccharide (LPS), were decreased in exposed fish. Also nonstimulated proliferation was lower than in unexposed fish. ConA-activated responses returned to normal levels within 7 days after exposure, but LPS-activated responses were reduced throughout the 14 day follow-up. The capability of UVB-exposed fish to produce an antibody response was studied by intraperitoneal immunization with bovine γ-globulin (BGG). The concentration of anti-BGG antibodies in plasma as well as the number of anti-BGG–specific antibody-secreting cells in the spleen or blood were not decreased in fish exposed either to a single dose of UVB prior to immunization, or to single dose of UVB prior to immunization followed by three additional doses after immunization. Immunoglobulin M (IgM) production, when assayed as plasma IgM level or as the number of IgM-secreting cells in the spleen or blood, was not suppressed after exposure to UVB irradiation. These results indicate that a single dose of UVB or short-term exposure to UVB irradiation has no negative effects on IgM production or reactivity against antigen administered via the intraperitoneal route. However, the suppression of in vitro lymphoproliferative responses suggest that exposure to UVB has the potential to interfere with lymphocyte-related functions in fish.

Additive effects of enhanced ambient ultraviolet B radiation and increased temperature on immune function, growth and physiological condition of juvenile (parr) Atlantic Salmon, Salmo salar

Climate change models predict increased ultraviolet B (UVB) radiation levels due to stratospheric ozone depletion and global warming. In order to study the impact of these two environmental stressors acting simultaneously on the physiology of fish, Atlantic salmon parr were exposed, for 8 weeks in outdoor tanks, to different combinations of UVB radiation (depleted and enhanced) and temperature (standard rearing temperature of 14 °C or 19 °C). The immune function (plasma IgM, lysozyme activity and complement bacteriolytic activity), growth (body weight) and physiological condition (haematocrit and plasma protein concentration) of the fish were determined. Increased UVB level, regardless of water temperature, had a negative effect on immune function parameters, growth and physiological condition. Higher temperature increased plasma IgM concentration but had a negative effect on complement bacteriolytic activity under both spectral treatments. Increased temperature, irrespective of UVB level, increased fish growth but negatively affected haematocrit and plasma protein. Exposing the fish to enhanced UVB at elevated temperature increased plasma IgM concentration and slightly improved growth. However, complement activity and physiological condition parameters decreased more than when the fish were exposed to each stressor separately. The changes were mainly additive; no interactive or synergistic effects were observed. The negative impact of multiple stressors on immune function, together with predicted increases in pathogen load in warmer waters resulting from global climate change, suggest an increased risk to diseases in fishes.

Effects of ultraviolet light on immune parameters of the roach

Ultraviolet B radiation penetrates into water and can affect fish health and the immune system, as is the case with mammals. Teleost fish, the roach, were exposed to UVB irradiation in aquariums and a panel of immune parameters was determined. In addition to altered blood picture and respiratory burst by blood leukocytes, changes were noted also in major lymphatic organs. Respiratory burst and natural cytotoxicity activity of head kidney granulocytes and mitogen-activated proliferation of splenic lymphocytes were suppressed. Although mostly transitory, some parameters remained suppressed for the following 2 weeks. Ultraviolet A radiation had only minor effects. The stress induced by UVB may be involved in the modulation of immune parameters.

Modulation of immune parameters of roach, Rutilus rutilus, exposed to untreated ECF and TCF bleached pulp effluents

Abstract The present study was designed to assess the effects of elemental chlorine free (ECF) and totally chlorine free (TCF) pulp and paper mill effluents on the immune defence of the roach ( Rutilus rutilus ). Fish were exposed for 5 weeks to concentrations of 0, 0.6, 2, 6 and 20% of untreated effluents from ECF or TCF bleaching processes. In order to study the capability to respond to foreign antigens the fish were immunised with bovine γ-globulin (BGG) 3 weeks before sampling. The numbers of anti-BGG antibody-secreting cells and immunoglobulin-secreting cells in the spleen and blood, as well as the levels of the anti-BGG antibodies and concentrations of immunoglobulin in plasma and the proliferation of lymphocytes after mitogenic activation were determined. In addition, phagocytosis-related functions, respiratory burst activity and migration of leukocytes, were measured. Formation of specific anti-BGG antibody-secreting cells in the blood and immunoglobulin-secreting cells in the spleen and blood were suppressed in the fish exposed to a high concentration (20%) of ECF effluent. Similarly, the level of anti-BGG antibody and the stimulation indices of Concanavalin A-stimulated proliferation responses in vitro were lower in these fish. A decreased migration of granulocytes was observed in the fish exposed to 0.6–2% of ECF and TCF effluents. These results demonstrate that untreated ECF and TCF effluents significantly affected the immune parameters of the roach. Taken as a whole, fish exposed to TCF effluent showed less immunomodulation than those exposed to EFC effluent.

Long-term UVB Irradiation Affects the Immune Functions of Carp (Cyprinus carpio) and Rainbow Trout (Oncorhynchus mykiss)

The effects of long‐term, low‐dose ultraviolet B (UVB) radiation on immune functions of two fish species representing different taxonomic groups, carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), were assessed in this study. The fish were exposed to 7, 20 or 60 mJ cm−2 UVB three times per week, for 6 weeks. In carp, UVB exposure affected the respiratory burst activity of blood and head kidney phagocytes, differential blood leukocyte counts and blood chemistry. Phytohemagglutinin (PHA)‐stimulated in vitro proliferation responses of blood and head kidney lymphocytes, however, remained unchanged. Rainbow trout tolerated the irradiations with fewer alterations, but significant changes were detected in blood chemistry and hematocrits of the irradiated fish. These results indicate that long‐term exposure to low doses of UVB induces immunomodulation in fish, and that there are species‐specific differences in sensitivity to irradiation.