Structural and functional analysis of spontaneous anti-nitrophenyl antibodies in three cyprinid fish species: carp (Cyrinus carpio), goldfish (Carassius auratus) and tench (Tinca tinca).

High spontaneous anti-trinitrophenyl (TNP) activities were found in three Cyprinid fish species: Carp (Cyprinus carpio), Goldfish (Carassius auratus) and Tench (Tinca tinca). The molecules involved, isolated by affinity chromatography on dinitrophenyl-lysine Sepharose (DNP-lysine-Sepharose), had the main characteristics of a high molecular weight immunoglobulin (IgM-like). Affinity measurements were performed on natural anti-DNP/TNP antibodies isolated from nine individual tench sera, using the inhibition of DNP-T4 bacteriophage inactivation technique. The antibodies analysed were more specific for TNP than for DNP. No activity was found against paranitrophenyl hapten. Affinities were all very low, even for TNP. In the three species, natural anti-DNP/TNP antibodies constitute as much as 11 to 16% of the total immunoglobulin concentration. This high level of nitrophenyl-binding serum immunoglobulins either suggests the existence of a particular regulatory mechanism in fish or reflects a generally low antibody diversity in these species.