Interleukin-1 in fish

It has been known for over a decade that IL-1 bioactivity exists in fish. Recently IL-1 has been cloned in several teleost species using two different approaches; homology cloning or a suppression subtractive PCR technique. One of the most important differences of the fish sequences compared with mammalian IL-1 is the lack of a clear ICE cut site, and it remains to be determined whether the fish molecule is processed to a mature peptide. The IL-1 gene organisation has also been determined for rainbow trout, and Southern blot analysis suggests at least one related gene is present in this species. Expression of the IL-1 transcript can be induced in vitro by stimulation of head kidney leucocytes with LPS or PHA, or in vivo by challenge with Gram-negative bacteria. A number of incompletely spliced transcripts have also been detected in tissues from challenged fish.