IMMUNOSUPPRESSION IN JUVENILE CARP, CYPRINUS-CARPIO L - THE EFFECTS OF THE CORTICOSTEROIDS TRIAMCINOLONE ACETONIDE AND HYDROCORTISONE 21-HEMISUCCINATE (CORTISOL) ON ACQUIRED-IMMUNITY AND THE HUMORAL ANTIBODY-RESPONSE TO ICHTHYOPHTHIRIUS-MULTIFILIIS FOUQUET

Abstract. Juvenile carp, Cyprinus carpio L., were immunized against Ichthyophthirius multifiliis following controlled exposure to the infective theront stage. On challenge, with a potentially lethal dose of theronts, all immunized fish survived, in contrast to 100% mortality in non‐immunized fish. Fourteen days following exposure to the challenge infection, immune and non‐immune fish were injected intraperitoneally with either triamcinolone acetonide or hydrocortisone 21‐hemisuccinate (cortisol) at doses of 100 μg or 10 μg/g body weight. Controls, including immunized and non‐immunized fish, were injected with saline or left untreated. Six days following corticosteroid administration, fish were exposed to challenge infections of I multifiliis. All fish treated with corticosteroid developed heavy infections with up to 100% mortality. Repeat experiments gave comparable results. Serum antibody levels recorded in similarly treated fish at intervals of 12 h and/or 1 week following corticosteroid administration were found to be relatively unaffected. The results are discussed in relation to the immune response to I multifiliis. Copyright © 1990, Wiley Blackwell. All rights reserved