Invertebrate and fish cytokines

Cytokine-like molecules are well described in invertebrates, although most recent studies have revealed that there is analogy, rather than homology, b etween invertebrate and vertebrate cytokine-like activities. Cytokines cert ainly appeared early in the evolution of vertebrates, dating back some 400 millions years. Here, evidence will be reviewed and updated of the presence of these molecules in jawed fish and in particular, in bony fish, which re present the oldest group displaying true functionality of immune system as known in modern vertebrates. Many studies during the last ten years have co nfirmed the presence of functional homologues of mammalian cytokines in fis h. In this review, particular attention will be focussed on IL-1 beta, a ve ry ancient defence cytokine recently sequenced in two species, rainbow trou t (Oncorhynchus mykiss) and carp (Cyprinus carpio), Original data on the pa rtial peptide sequence of IL-1 beta in the mediterranean sea bass Dicentrar chus labrax are also presented.