In the present study, FBL-3 murine erythroleukemia cells were transfected with human OSM(hOSM) gene by recombinant adenovirus, then the immunological properties of hOSM gene-transfected FBL-3 celIs(FBL-3-OSM⁺) were investigated. 4 hours after transfection with hOSM gene, hOSM could be detected in the supernatant of FBL-3-OSM⁺ cells and hOSM secretion peaked at 24 h. The proliferation of FBL-3-OSM⁺ cells was inhibited markedly. The clonal formation of FBL-3-OSM⁺ cells was suppressed more obviously in comparison with wild-type FBL-3 cells when analysed in clonal argar culture. Flow cytometry analysis showed that FBL-3-OSM⁺ cells expressed higher levels of Fas protein, B7 and ICAM-1 molecules.FBL-3-OSM⁺ cells also expressed higher level of MHC class I molecules(H-2K b) but remained unchanged in expression of MHC class II molecules (Ia). CDI4, which is a specific marker of monocyte/macrophage and not expressed on the wild-type FBL-3 cells, was also detected on the surface of FBL-3-OSM⁺ cells. The results suggested that OSM gene transfer could increase the immunogenicity of FBL-3 cells and promote their differentiation into macrophage-like cells. The data outline a promising approach to OSM gene therapy of leukemia mediated by recombinant adenovirus.