The purification and characterization of rat gamma interferon by use of two monoclonal antibodies

Summary Two mouse monoclonal antibodies, designated DB-1 and DB-2, were isolated and used for the purification and characterization of recombinant rat interferon gamma (rRIF-γ) derived from Chinese hamster ovary (CHO) cells. The two antibodies belong to different classes (DB-1 is an IgG1 and DB-2 an IgA) and display similar epitope specificities as shown in competition binding experiments. Both antibodies, raised against rRIF-γ, exhibited high affinity for rat and mouse gamma interferon and efficiently neutralized the antiviral activity of both animal interferon species. Affinity chromatography analysis showed that a column with immobilized DB-1 was capable of complete binding of rat and mouse gamma interferon, both natural and recombinant DNA-derived. As visualized by SDS-polyacrylamide gel electrophoresis and Western blot analysis, the purified rRIF-γ preparation consisted of at least seven molecular forms with M r values ranging between 14000 and 25000, with a relative abundance of a 18000 M r protein. Gel permeation chromatography of crude rRIF-γ gave coincident peaks of rRIF-γ proteins (all different forms) and interferon activity corresponding to a M r value of 45000. The results suggest that the molecular heterogeneity was due to differential glycosylation and was not the consequence of a proteolytic degradation process.