Molecular cloning of the gene for interleukin-1 beta from Xenopus laevis and analysis of expression in vivo and in vitro

The Xenopus cDNA for interleukin-1 beta (IL-1B) was cloned and sequenced. T he gene contains 1462 nucleotides that translate in a single reading frame to give a predicted 283-amino acid IL-1 beta molecule. The translated molec ule contains a single potential glycosylation site, a readily identifiable IL-1 family signature, and has highest homology to chicken IL-1 beta by phy logenetic tree analysis and sequence similarity. It lacks a signal peptide in common with other known IL-IB genes, and lacks a clear ICE (caspase) cut site in common with other nonmammalian IL-IB genes sequenced to date. RT-P CR was used to study sites of IL-IB transcript expression, 24 h following i njection of lipopolysaccharide (LPS). Expression was detected in the brain. liver, kidney, and spleen, with expression weakest in the brain and strong est in the spleen. No transcript expression was detectable following inject ion of saline. Northern blot analysis was used to quantify the induction of IL-IB expression in splenocytes following in vivo or in vitro stimulation with LPS. The results are discussed in relation to the potential role of IL -1 beta in amphibian immune responses.