Serum lectins in fish innate immunity: molecular and functional aspects

Fucose-binding lectins (FBL) are present in tissues and fluids from invertebrates and vertebrates. The lectin repertoires in teleost fish are highly diversified and recently has been described the structure of the fucose-binding agglutinin that revealed a novel lectin fold (the “F-type” eel (Anguilla anguilla) fold), which shared a unique fucose-binding sequence motif contained both in carbohydrate-binding proteins and unrelated proteins. In this report, we describe serum FBL from sea bass Dicentrarchus labrax and sea bream Sparus aurata. These lectins were purified, characterized, cloned and sequenced. Studies on structural aspects, biological activity, tissue distribution as well as ontogenetic aspects were carried out. In addition, results on inflammatory response and opsonic activity against bacteria suggested that D. labrax FBL is involved in innate immunity. Finally a new galactose binding lectin with agglutinating activity against bacteria purified from Dicentrarchus labrax serum was also described and compared with FBL.