Role of interleukin-1β in immune responses of rainbow trout

The first fish interleukin-1β (IL-1β) sequences have recently been isolated in fish, in rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar), carp (Cyprinus carpio) and plaice (Pleuronectes platessa). These sequences have some 48–56% amino acid similarity to known mammalian IL-1β sequences. The gene organisation of the trout and salmon genes have been determined and have one intron less, relative to the mammalian genes. Expression studies have shown that these genes are inducible after stimulation with LPS or PHA in vitro or after bacterial challenge in vivo. Several incompletely spliced transcripts can be detected by RT-PCR. Southern blot analysis suggests at least two IL-1β (or related) genes are present. More recently the trout IL-1β promoter has been sequenced and shown to contain a number of regulatory elements. Recombinant trout IL-1β has been produced and the biological activity of this and IL-1β peptides has been studied.