RECOMBINANT MURINE (RM) INTERLEUKIN (IL)-5 ENHANCES THE EOSINOPHIL PEROXIDASE CONTENT IN CELLS CULTURED IN-VITRO COMPARED WITH RMIL-3 AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR

We previously reported an in vitro bioassay permissive to eosinophil p roduction from naive mouse bone marrow cells. Based on cytosmear analy sis, recombinant murine (rm) interleukin (IL)-3 combined with granuloc yte-macrophage colony-stimulating factor (GM-CSF) provided better quan titative cellular yields compared with rmIL-5. In the present study, w e compared the eosinophil peroxidase (EPO) content obtained in both in vitro conditions using microtitration. Parallel with the EPO assay, t he percentage of eosinophils present in cultures was determined by cyt osmear analysis. Cells incubated with IL-5 displayed significantly hig her EPO activity than those cultured in the presence of IL-3 and GM-CS F. At the end of the culture period, cells were further enriched in eo sinophils as determined by centrifugation gradient. Enhanced amounts o f cellular EPO were detected when cultures were performed in the prese nce of IL-5. With regard to the correlation between eosinophil maturat ion and EPO acquisition, eosinophil cells cultured with rmIL-5 express ed significantly more EPO activity than those generated in the presenc e of rmIL-3 and GM-CSF.