Red-complex bacteria: immunological background leading to the development of head and neck cancers

Oral microbiome imbalance is involved in the development of head and neck cancers (HNCs). There is a group of oral pathogens, such as Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, that creates red-complex. Currently, the oral pathogens' role in the pathogenesis of periodontitis is well-described; nevertheless, data regarding the link between HNCs and periopathogens are still limited, especially considering T. forsythia and T. denticola. These microbes utilise various virulence factors to promote the carcinogenesis process, affecting the immunological background. This paper presents modern insights into the role of red-complex bacteria in the development of HNCs, concentrating on the immunological aspects.