ISOLATION AND CHARACTERIZATION OF PORCINE CATIONIC EOSINOPHIL GRANULEPROTEINS

The allergic pig can be used as a large-animal model for studies of al lergic reactions in the airways and the role of eosinophils in such re actions. To measure the activation of eosinophils, the release of eosi nophil-derived cationic proteins can be used. The purpose of this stud y was to isolate and characterize cationic proteins derived from porci ne eosinophils. Pigs were infested with live Ascaris suum eggs to indu ce eosinophilia (greater than or equal to 40% of leukocytes). Blood wa s collected and leukocytes were prepared by dextran sedimentation, Gra nules were obtained from the homogenized leukocytes by ultracentrifuga tion and cationic proteins were extracted and separated by gel filtrat ion, cation exchange and zinic affinity chromatography. Using these me thods, three cationic proteins were isolated from pig granulocytes, tw o of which were shown to originate from the eosinophil. The proteins w ere characterized according to molecular weight, amino acid compositio n, N-terminal sequence, isoelectric point, peroxidase and ribonuclease activity and antigenicity. One eosinophil protein was identified as e osinophil peroxidase and the other showed great similarities with huma n eosinophil cationic protein. The third protein was not specific for eosinophils, and had no obvious equivalent in human granulocytes. The eosinophil-derived proteins may be useful in the studies of eosinophil activation, e.g. in late-phase asthmatic reactions, where the pig rep resents a new candidate model for large-animal allergy research.