Delphinidin Chloride and Its Hydrolytic Metabolite Gallic Acid Promote Differentiation of Regulatory T cells and Have an Anti-inflammatory Effect on the Allograft Model

Regulatory T cells (Tregs) control the reactivity of other T cells to prevent excessive inflammatory responses. They also plays a role in preventing autoimmune diseases; but when they are overproduced, they decreased vital immunity, which can lead to invasion of external pathogens. Therefore, it is most important in preventing the development of immune diseases to maintain the homeostasis of these cells. Delphinidin chloride is an anthocyanidin and known to have anti-oxidant activities. However, its structure is very unstable and easily decomposed. One of these degradation products is gallic acid, which also has anti-oxidant effects. In this study, we examined the effect of these materials on Tregs in controlling immune response. It was found that these materials further promote differentiation into Tregs, and TGF-beta and IL-2 related signals are involved in this process. Furthermore, it was verified that a variety of immunosuppressive proteins were secreted more, and the function of induced Tregs was also increased. Finally, in the allograft model, we could find a decrease in activated T cells when these materials were treated because they increased differentiation into Tregs. Therefore, these two materials are expected to become new candidates for the treatment of diseases caused by excessive activation of immune cells, such as autoimmune diseases. Practical Application Delphinidin, a kind of anthocyanin rich in pigmented fruits, and its hydrolytic metabolite, gallic acid, are known to have antimicrobial and anti-oxidant properties. In this experiment, it was shown that delphinidin and gallic acid had an effect of increasing the differentiation of regulatory T cells, and the effect of suppressing the function of memory T cells was also observed. Due to these functions, delphinidin and gallic acid might have the potential to be used as immune suppressive agents in organ transplant and autoimmune disease patients or be a model for food development associated with the immune system.