Cloning, expression, biologic properties, and transcription during endotoxemia

The cloning, sequencing, expression, and biologic activities of rabbit IL-1 α and β are described. A cDNA library was constructed in λgt10 by using polyadenylated RNA extracted from rabbit adherent splenic macrophages 4 h after stimulation with endotoxin. By using the cDNA for human IL-1β and IL-1α as hybridization probes, cDNA for both forms of rabbit IL-1 were isolated. The cDNA for rabbit IL-1β encodes a precursor polypeptide of 268 amino acids with an overall homology to human IL-1β of 74% (81% in the mature region coding for a 17.5 kDa carboxyl-terminal protein). The similarity between the two rabbit IL-1 forms is 31% for the entire molecule and 34% for the mature protein. The mature polypeptides of both forms were expressed in Escherichia coli. The recombinant proteins were purified to homogeneity and tested in a variety of biologic assays. Both forms produced typical endogenous pyrogen fevers in rabbits and augmented murine thymocyte and Th cell proliferation. Rabbit IL-1 α and β were more pyrogenic in rabbits than human rIL-1β, whereas human rIL-1 α and β were slightly more potent lymphocyte-activating factors. The recombinant rabbit proteins induced PGE and IL-1 production from human PBMC in vitro. A RIA for human IL-1α did not recognize rabbit IL-1 α or β, but rabbit IL-1β cross-reacted (as much as 30%) in a RIA for human IL-1β. Rabbits were injected with endotoxin and mRNA for both forms of IL-1 were observed primarily in the spleen and liver. The mRNA reached maximal levels after 60 min, then declined rapidly over the next 3 h, but were still present after 24 h. Liver tissue removed 4 h after endotoxin infusion produced lymphocyte-activating factors which were neutralized by more than 90% with a combination of goat anti-rabbit IL-1α and anti-IL-1β.