Inducible lectins with galectin properties and human IL1α epitopes opsonize yeast during the inflammatory response of the ascidian Ciona intestinalis

Abstract

Studies on inducible ascidian lectins may shed light on the evolutionary emergence of cytokine functions. Here, we show that the levels of opsonins, with IL1alpha-epitopes, increase in Ciona intestinalis hemolymph as a response to an inflammatory stimulus and, in particular, to intratunic injection of lipopolysaccharide (LPS). The inflammatory agent promptly (within 4 h) enhances Ca(2+)-independent serum hemagglutinating and opsonizing activities, which are both inhibited by D-galactose and D-galactosides (alpha-lactose, N-acetyl-D-lactosamine, thio-digalactoside), suggesting that anti-rabbit erythrocyte lectins with galectin properties are involved as opsonins. Inducible galectin molecules contain interleukin-1alpha (IL1alpha) epitopes, and their activities are specifically inhibited by anti-human recombinant IL1alpha antibody. Analysis by SDS-polyacrylamide gel electrophoresis has revealed that the density of the bands of several serum proteins increases within 4 h after LPS injection, correlated with the enhanced serum activity. Moreover, Western blot patterns demonstrate that several serum proteins (59, 37, 30, 23, 15 kDa) cross-react with the antibody as early as 4 h post-injection. Although we have not been able to establish whether, in adition to galectins, various types of D-galactose-specific lectins are contained in the serum, we show, for the first time in invertebrates, that galectin molecules with opsonic properties can be enhanced in response to a non-specific inflammatory stimulus, and that their release can be further stimulated by LPS. Finally, we reveal that multiple galectins share human IL1alpha epitopes, probably because of steric configuration and the oligomerization process.