Formation Mechanisms And Functions Of Macrophage Polarization And Multinucleated Giant Cell In Mycobacterial Infection

Macrophages are characterized by mobility, plasticity and adaptability that belong to the myeloid lineage. They are ubiquitously present in tissues, where they adjust to local tissue environment and play an important role in the host inflammatory response and the process of tissue repair and remodeling following injury. Macrophages have been classified as having plastic phenotypes which exist along a spectrum between M1 type and M2 type. M1 refers to macrophages activated by bacterial lipopolysaccharide (LPS) or interferon (IFN)-γ, while M2 refers to macrophages activated by IL-4, IL-10, IL-13. M1 possesses characteristics which include production of large amounts of pro-inflammatory signaling and effector molecules, efficient antigen presentation, killing of intracellular pathogens, tumor destruction, and promotion of polarized Thl responses. M2 possesses immune-regulatory or tissue remodeling characteristics which include minimal production of pro-inflammatory molecules, expression of scavenger, mannose, and galactose receptors, increased phagocytic activity, and participation in polarized Th2 reactions. However, heterogeneity and plasticity of macrophage phenotype are increasingly recognized as playing an important role in the response to pathogens and tissue injury as well as in the development and progression of a variety of diseases. Transition between M1 and M2 phenotype occurs concurrently in different environment. In specific and rare instances, macrophages are attracted to one another and fuse to form multinucleate giant cells (MGCs) in chronic inflammatory sites.Chapter Ⅰ:Evaluate the ability to induce the formation of multinucleated giant cells by different cytokines. GM-CSF combined with IFN-γ or IL-4 promoted macrophages fusion rate, as well as IL-3. But macrophages fusion did not improved by stimulation of only GM-CSF or IL-3. Similar to M. leprae in vitro, GM-CSF and IFN-γ induced fusion leading to the formation of Langhans cells which is consistently circular or ovoid in shape with a limited number of nuclei, often arranged in a characteristic circular or semi-circular "horseshoe" pattern.Chapter Ⅱ:Reveal the mechanism for the formation of different multinucleated giant cells. Recently a Multinucleation Gene Network in Macrophages mainly including MMP-9, P2rx7, PIK3cb, Osp, CD9 and Ctsk were identified. We analyzed these genes in macrophage fusion in vitro by real-time PCR. Tm7sf4, PIK3cb, Osp were related with Langhans cells information induced by IFN-γ and GM-CSF; CD36, Tm7sf4 were involved in the macrophages fusion stimulated by IL-4; Tm7sf4, PIK3cb, Osp expressed in Langhans cells induced by M. leprae in vitro.Chapter Ⅲ:Evaluate Macrophage polarization and the expression and secretion of cytokines of Macrophage and MGCs. GM-CSF combined with IFN-y induced M1 macrophage,while GM-CSF combined with IL-4 induced M2 macrophage. Both of M1 and M2 macrophage could fuse to MGCs. In early stage M1 secreted Thl cytokine such as IL-1β, TNF-α. M2 secreted Th1 and Th2 cytokine IL-10. Meanwhile, we found that M1 and M2 macrophage coexist in GM-CSF+IFN-γ group and GM-CSF+IL-4 group by f lowcytometrty and confoeal laser scanning microscopy. Cytokine secretion and Transition between M1 and M2 phenotype had some relationship. Macrophage stimulated by M. leprae expressed and secreted Th1 cytokine IFN-γ, IL-1β and Th2 cytokine IL-10 Both M1 and M2 macrophage play important roles in mycobacteria infection. M1 macrophage iduced by IFN-γ and Macrophage stimulated by M. leprae secreted IL-15 which is associated with cell fusion.Chapter Ⅳ:Assess phagocytosis function and bactericidal effect of M1 and M2 macrophage and their related multinucleated giant cells. M2 type macrophage and MGCs induced by IL-4 possessed stronger phagocyte than M1 type induced by IFN-γ. M1 type macrophage had more effective bactericidal function than M2, which decreased along with the maturation of MGCs.Overall, we established an in vitro model of macrophage polarization and MGCs, and investigated the characteristic of M1 and M2 macrophage and MGCs. This method can be applied to the study of innate immune response to mycobacteria infection.