Immunization and culture of rainbow trout organ sections in vitro.

Splenic and anterior kidney sections or whole organs were excised from large (1 kg) or small (200 g) rainbow trout (Salmo gairdneri) and placed in sterile 60 mm plastic plates containing 10 ml of Eagle's minimal essential medium (EMEM) supplemented with normal or fetal calf serum for in vitro culture. The organ samples were immunized in vitro by direct injection or by mixing in the medium Yersinia ruckeri O-antigen or dinitrophenyl-Ficoll. The medium was changed once during the 10-day incubation at 15 C. The passive hemolytic plaque assay demonstrated antibody production from the plaque-forming cells (PFC); passive hemagglutination was used to measure antibody titers in the media. High numbers of PFC occurred in cultures of either kidney or spleen, demonstrating that these organs can function independently for antibody production. Splenic sections from large fish produced more PFC than comparable whole organs from small fish. EMEM supplemented with 2% normal calf serum was a satisfactory culture medium. 2-hydroxyethyl-mercaptan an ingredient used in mammalian cell culture, inhibited antibody production in trout cells. These techniques are being used in the culture of organs and cells to elucidate pathways and sequences of antigen uptake and delivery of the immunopoietic tissues in trout.