Kinetics of juvenile sea bass (Dicentrarchus labrax, L.) systemic and mucosal antibody secreting cell response to different antigens (Photobacterium damselae spp. piscicida, Vibrio anguillarum and DNP)

The ELISPOT assay was used to measure the number of specific antibody secre ting cells (ASC) induced during the primary and secondary immune responses in the spleen, head kidney and gut of juvenile (5 g) sea bass (Dicentrarchu s labrax) to bacterial (Vibrio anguillarum and Photobacterium damselae ssp. piscicida) and hapten dinitrophenyl-conjugated to keyhole limpet haemocyan in (DNP-KLH) antigens administered intraperitoneally. High variability amon g individuals was observed at each sampling day. All fish were bath vaccina ted to V. anguillarum at an earlier stage (2 g) in the farm of origin prior to the development of the experiments, and therefore only secondary and te rtiary responses were measured in the group immunised with this bacterium. Significant differences to the controls were observed in the primary respon ses of the head kidney and the spleen to P. damselae ssp. piscicida and DNP , respectively. Frequency analysis of the production of ASC suggests that s ignificant responses in the gut might be masked by the high error variance. The peak of the primary response was observed 4 days earlier to DNP (18-20 days post-immunisation) and it was significantly higher than the response to P. damselae ssp. piscicida. Higher numbers of ASC were observed in the s econdary responses of the head kidney and spleen, although they were not st atistically significantly different from the primary levels, probably due t o the high error variance as supported by the frequency analysis. Neverthel ess, together with a faster response (peak at 7 days post-immunisation), th e data suggest that memory formation had occurred. Additionally, the data s uggest that some suppression of the secondary immune response in the gut mi ght have occurred. The head kidney appears to produce the highest number of specific ASC of the organs tested. It appears that sea bass show a relativ ely fast but short duration antibody response. (C) 2001 Academic Press.