Cloning and bioactivity of fish cytokines and their relevance to disease resistance

Cytokines are the signalling molecules within the immune system. Typically they have a low constitutive expression but on stimulation by infection or an inflammatory insult they are rapidly turned on. They can both initiate and regulate inflammatory reactions and several are important accessory factors required for optimal stimulation of the specific defences. Within fish several of the key cytokine genes have been cloned in recent years, including molecules such as interleukin-1beta (IL-1beta)(Zou et al., 1999; Scapigliati et al., 2001), tumor necrosis factor a (TNFa)(Hirono et al., 2000; Laing et al., 2001), transforming growth factor-beta (TGF-beta)(Hardie et al., 1998; Laing et al., 2000), and several chemokines (see below for definition) including IL-8 (Laing et al., in press) and gamma interferon inducible protein (gammaIP)(Laing & Secombes, 2001) amongst others (Dixon et al., 1998; Kono Sakai, 2001).