Dying cells have been shown to stimulate dendritic cell maturation and migration to the lymph node,suggesting that dying cells may act as immunostimulatory adjuvants.However, we found that dying cells induced one cell type to proliferate and differentiate into phagocytes in vitro.In the present study,the biological characteristics of these differentiated phagocytes were studied.We found that the differentiated cells were large cells with an irregular outline, and generally displayed uropoda,laminations, membrane folding, and vesicles on the cell surface.The predominant cytoplasmic organelles were lysosomes, secondary lysosomes and residual bodies.In addition, the rough endoplasmic reticulum and lipid bodies were abundant in the cytoplasm and numerous larger mitochondria with a low electron density matrix were observed in the cytoplasm.The percentage of CD1 4, CD68, CD80, CD86 and MHCⅡ positive cells within the differentiated population were 53.9%,98.6%, 26.5%, 90.2% and 25.4%, respectively.In addition, the phagocytic index and percentage of phagocytic cells were significantly higher in differentiated phagocytes than in GM-CSF-induced macrophages and ascites macrophages.Our results indicate that the differentiated phagocytes induced by dying cells possess characteristics that are similar to macrophages.