Abstract: Multinucleated giant cell ( MGC ) is one of the characteristic pathological cells in infections with Mycobacterium species,especially Mycobacterium tuberculosis (MTB).Typical MGCs have large volume with multiple nuclei in a ringlike or horseshoe-shaped arrangement in the cytoplasm.In general,MGCs are formed by the differentiation and fusion of monocyte-macrophage cells in the microenvironment of granuloma.Although MGCs have been discovered for a long time,little is known about their formation mechanism,function,and significance for host and mycobacteria.Many studies have shown that the formation and functional changes of MGCs are affected by some components and secreted proteins of mycobacteria,numerous cytokines and adhesion factors in the microenvironment of granuloma,cell surface antigen,and so on.