DIFFERENTIAL SYNTHESIS, CELLULAR-LOCALIZATION AND SECRETION OF INTERLEUKIN-1-ALPHA AND INTERLEUKIN-1-BETA FROM OVINE MACROPHAGES

In order to characterise the regulatory processes involved in expressi on of ruminant interleukin 1 (IL-1) biological activity, we have used specific monoclonal antibodies to assess synthesis, cellular localisat ion and secretion of ovine IL-1 alpha and IL-1 beta from alveolar macr ophages. Immunoprecipitation of IL-1 alpha and IL-1 beta from lysates of macrophages cultured in media alone or media supplemented with lipo polysaccharide (LPS) revealed that both forms of IL-1 were synthesised as precursor proteins of 31-33 kDa. In contrast, both IL-1 species we re immunoprecipitated from culture supernatants as 17 kDa molecules. C omparison of the precipitated bands from culture supernatants suggeste d that significantly more IL-1 beta than IL-1 a was secreted by the ma crophages. Flow cytometric analysis of IL-1 alpha and IL-1 beta expres sion by fresh unstimulated macrophages and macrophages cultured for 5 h with LPS demonstrated that a proportion of the cell associated IL-1 alpha, but not IL-1 beta, in stimulated macrophages was expressed at t he cell surface. Analysis of IL-1 secretion by cultured alveolar macro phages, using IL-1 alpha and IL-1 beta specific immunoassays, confirme d that IL-1 beta was the predominant secreted species of IL-1. While c ell associated IL-1 alpha and IL-1 beta were detected by immunoprecipi tation and flow cytometric analysis of macrophages cultured in media a lone or media supplemented with LPS, secreted IL-1 beta was detected o nly after stimulation of macrophages with LPS. This indicates a dissoc iation of IL-1 beta synthesis and secretion and is indicative of an IL -1 beta converting enzyme similar to that which has been described in the human and mouse models.