Immunocytochemical characterization of a monoclonal antibody that recognizes mitosing cells

The isolation and characterization of a monoclonal antibody (C5F10) which identifies dividing cells in normal and neoplastic tissues (carcinomas, sarcomas, and lymphoreticular malignancies) in formalin-fixed, paraffin-embedded sections is described. The antibody also recognizes rapidly dividing cells in normal and transformed cells in culture. A combination of autoradiography with 3H-thymidine and immunochemical localization of C5F10 showed that cells in S-phase of the cell cycle were weakly stained for C5F10, while dividing cells stained intensely with this antibody. The target structure of C5F10 appears to be different from the commonly recognized microtubule, intermediate filament and microfilament proteins and from the proliferating cell nuclear antigen (cyclin). This antibody may be a useful tool for readily detecting dividing cells in cell cultures and in tissue sections and may prove useful in studies to analyze the molecular basis of cell growth.