Establishment of a Macrophage-activating Factor Assay System Using the Human Monocytic Cell Line THP-1

Background: As the mechanism of macrophage activation is not well-understood, standardization of an assay system for measuring phagocytic activities of macrophages will be useful for research on macrophages. Previously, we established a novel standardized macrophage-activating factor (MAF) assay system using U937. Materials and Methods: Using the human monocytic cell line THP-1, another standardized MAF assay system was established. Characteristic gene expression of U937- and THP-1-derived macrophages was compared by gene expression microarray analysis. Results: Both U937- and THP-1-derived macrophages showed obvious phagocytic activities with unique characteristics and, therefore, could not be assigned to a single sub-type. Conclusion: Activation of macrophages is an intricate cellular process. Comparison of our two novel assay systems provides new insights into macrophage activation mechanisms.