Ultraviolet B irradiation modulates the immune system of fish (Rutilus rutilus, Cyprinidae). Part III: Lymphocytes.

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 gamma-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.

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.