Immunomodulatory properties of dietary polyphenols: a role for combating infections at mucosal surfaces?

Polyphenols are food components with antioxidant and anti-inflammatory properties, and their health benefits are increasingly recognized in the context of noncommunicable diseases such as type 2 diabetes. However, their role in regulating immunity to infection is not well understood. Here, we highlight the various mechanisms by which polyphenols may enhance mucosal immunity via both adaptive and innate immune responses. Polyphenols may directly interact with host receptors on mucosal epithelial and/or immune cells to regulate production of cytokines and antimicrobial peptides. In addition, polyphenols can also modify gut microbiota composition, yielding microbial-derived metabolites that play a key role in fine-tuning immune function at mucosal surfaces.  We provide examples of how these immunological changes may alter the outcome of pathogen infection and propose that an increased understanding of polyphenol-microbiota-immune interaction will provide a framework for the application of new nutrition-based strategies in the management and prevention of infectious diseases.