[Relationship between differentiation of U937 cells and free-radicals-associated proteins on the membrane]

U937, the human monocytic cell line does not have the ability to generate free radicals. However, this cell can be differentiate into a monocyte by stimulation with phorbol esters. In this study, whether differentiated U937 could generate free radicals upon stimulation with chemotactic peptide was examined. The amount of surface protein which was related to the generation of free radicals was quantitated using a monoclonal antibody, termed TM2, which reacted with free radical-associated proteins. There was great augmentation of TM2-associated protein in differentiated U937 cells compared with undifferentiated U937 cells. There were slight differences in the molecular weight of the TM2-associated protein among undifferentiated U937 cells, differentiated U937 cells and granulocytes. It seems necessary to increase some specific protein on the surface of U937 cells in order to generate free radicals.