Oral health and pathology: a macrophage account

Macrophages are functionally diverse, and mediate several important processes. Depending on activation and differentiation factors encountered in their microenvironment, they will express a pro-inflammatory phenotype (red), which has a predominant role in host defence (phagocytosis, microbial killing, inflammation, cell recruitment, antigen presentation, and priming of T cells), or an anti-inflammatory or regulatory phenotype (blue), which has a chief role in regulatory or tissue reparative mechanisms involved in homeostasis (phagocytose cellular debris, anti-inflammatory cytokine secretion, tissue repair, cell recruitment, and antigen presentation to induce tolerance).

The role of macrophages in oral disease. Macrophages display a diverse array of functions represented as a phenotypic spectrum from pro-inflammatory M1 to anti-inflammatory or regulatory M2 subsets. They can be activated to give an exaggerated or inappropriate response that can perpetuate oral disease. M1 macrophages can aid the progression of oral lichen planus and potentially induce malignant transformation. Conversely, M2 macrophages aid immunosuppressive disease such as oral squamous cell carcinoma (SCC).

Macrophages as potential therapeutic targets. M2 macrophages have the regulatory capacity to dampen down () chronic inflammation in oral lichen planus and prevent potential malignant transformation, and M1 macrophages can create the antitumoural environment required to resolve () oral squamous cell carcinoma (SCC).