Abstract: Objective To determine the volume change of mouse peritoneal macrophages after LPS-stimulation. Methods After stimulation with LPS for 3 and 24 hours, the cell morphological changes were observed under phase-contrast microscope, the content of IL-6 in the cell supernatant was measured with ELISA (enzyme linked immunosorbent assay), and the volume changes were analyzed with flow cytometry, respectively. Results In the normal condition, mouse peritoneal macrophages are round with smooth edge and without vacuoles. After stimulated by LPS, the surface area of mouse peritoneal macrophages become larger than before. Pseudopodium and vacuoles can also be seen and as stimulation time extended, their number increased. Especially after 24 hours, mouse peritoneal macrophages turned into fusiform, and their pseudopodia fused with each other. After LPS stimulation, we found the content of IL-6 in the cell supernatant increased dramatically, illustrating the secretory pathway of inflammatory factor has been activated by LPS and the peritoneal macrophages have been activated. Flow cytometry observed increasing FSC (demonstrating cell size) by 11% (P < 0.05) after 3 hours and 20.2% (P < 0.01) after 24 hours, as well as SSC (demonstrating paticles in cell surface) increased by 21.6% (P < 0.05) after 3 hours and 68% (P < 0.01) after 24 hours. Conclusions Flow cytometry can determine the volume changes of mouse peritoneal macrophages quantitatively, providing new method for studying the activation and function of innate immunity cells.

Key words: Key words ： LPS, macrophage, activation, flow cytometry