Cross-reactivity between microbial and tumor antigens.

The composition of the gut microbiota has a major impact on anticancer immunosurveillance. This effect is in part determined by systemic effects of bacterial or fungal metabolites, as well as by microbial ligands of pattern recognition receptors that modulate adjuvant signals and hence determine the general immune tonus. In addition, microbial antigens can elicit specific T lymphocyte responses that are cross-reactive with respect to tumor-associated antigens, hence inducing specific antitumor immune responses. Here, we discuss current evidence in favor of such cross-reactive anticancer/antimicrobial T cell response and delineate a methodology to demonstrate their actual importance for the immune control of malignant cells.