Macrophages display remarkable plasticity and can possess distinct functions in response to different environmental stimuli. Classically activated macrophages (M1 macrophages) are pro-inflammatory and have a critical role in host defense against infection, while alternatively activated macrophages (M2 macrophages) suppress inflammatory responses and associated with wound repair. Probiotic bacteria are reported to have a beneficial effect on the host immune status through their ability to modulate the macrophage polarization. Some probiotic strains are reported to activate macrophages to M1 phenotype to kill intracellular pathogens, while some other probiotics can induce M2 macrophages to exert the anti-inflammatory effect. Thus, this review will focus on the immunomodulatory role of probiotics in macrophage polarization and summarize the mode of action of probiotics in regulating macrophage plasticity. The detailed understanding of the immunomodulatory signaling effects of probiotic bacteria will broaden our understanding of how probiotics may regulate the immune system and find their therapeutic potentials for inflammatory diseases.
Keywords: Inflammation; M1 macrophage; M2 macrophage; Polarization; Probiotics.