Isolation and partial characterization of eosinophil granule proteins in rats--eosinophil cationic protein and major basic protein.

Peritoneal eosinophilia was induced in rats using Ascaris suum extract as an antigen, and characteristics of granule proteins of eosinophils collected from the peritoneal cavity were investigated. Peritoneal eosinophilia was induced by injection of the antigen solution into the peritoneal cavity of the immunized rats that had been orally administered with cyclophosphamide. Peritoneal cells were collected 48 h after injection of the antigen solution, incubated in plastic dishes, and nonadherent cells were collected as an eosinophil-rich fraction, from which granule proteins were extracted. Granule proteins were then purified by cation exchange chromatography, gel filtration, copper chelate affinity chromatography, and reverse-phase HPLC. Two distinct basic proteins of which molecular weights are 18- and 17-kD were obtained. Partial N-terminal amino acid sequence analysis revealed that the 18-kD protein and the 17-kD protein were homologous to the human eosinophil cationic protein (ECP) and the human and guinea pig major basic protein (MBP), respectively. Both the two proteins showed strong bactericidal activity against Escherichia coli and Staphylococcus aureus. These results indicate that rat eosinophils also possess ECP and MBP in their granules as well as human and guinea pig eosinophils.