As large animal models continue to play an important role in translating lung-directed therapeutic strategies from laboratory animals to man, there is an increasing interest in the analysis of endogenous regulators of inflammation at both a genomic and a therapeutic level. To this end we have sought to characterise the ovine ortholog of elafin, an important regulator of inflammation in man. We have isolated both the elafin cDNA and gene which have a similar structure to other species orthologs. Interestingly, we have isolated two alleles for ovine elafin, which contain a very high number of transglutamination repeats, thought to be important in binding elafin to the interstitium. The mainly mucosal mRNA distribution for ovine elafin suggests that ovine elafin may, like its human ortholog, have functions in innate immunity. This is supported by analysis of elafin and the related protein SLPI in ovine bronchoalveolar fluid in response to locally administered lipopolysaccharide and confirmation of them acting as 'alarm' antiproteases. We have also cloned the ovine elafin cDNA into an adenoviral vector and have demonstrated correct processing of the secreted protein as well as biological activity. Over-expression of ovine elafin in a lung-derived epithelial cell line has a protective effect against the enzymes human neutrophil and porcine pancreatic elastase. The identification of the ovine elafin gene and its translated protein are important in developing practical strategies aimed at regulating inflammation in the large mammalian lung.