Researchers at the Salk Institute have made significant strides in understanding the role of regulatory T cells, immune cells that suppress the body's response to its own tissues, thereby preventing autoimmune reactions. The study, published in Nature Communications, focuses on the protein Foxp3, identified as a critical player in determining the genome structure and function of regulatory T cells in mice.
Unraveling the Complexity of Immune Regulation
Regulatory T cells are akin to the body's peacekeepers, ensuring a harmonious internal environment by inhibiting other immune cells from attacking the body's own tissues. The behavior of these cells is influenced by their chromatin architecture—the three-dimensional organization of chromosomes—which determines the accessibility of certain genes to proteins such as Foxp3.
Professor Ye Zheng and Assistant Professor Jesse Dixon have discovered that Foxp3 is crucial in sculpting the unique chromatin architecture of regulatory T cells, promoting their immunosuppressive function. "Regulatory T cells are the peacekeepers in our body," says Zheng, co-senior author of the study. "Fully understanding the influence of Foxp3 on how these peacekeepers develop teaches us about how our immune system functions—and dysfunctions in disease."
A Structural Approach to Cellular Identity
The team embarked on mapping the 3D chromatin architecture of regulatory T cells to discern whether Foxp3 alters the chromatin structure to activate genes vital for the cells' function. They compared the chromatin architecture of regulatory T cells to effector T cells—cells that initiate attacks and mobilize other immune cells to fight. This comparison revealed unique Foxp3 binding regions exclusive to regulatory T cells.
Dongsung Lee, co-first author and former postdoctoral researcher in Dixon’s lab, remarks, "Comparing regulatory and effector T cells gave us a clear picture of Foxp3's impact on regulatory T cell identity, since Foxp3 is only seen in regulatory T cells."
The Architectural Ingenuity of Foxp3
The researchers identified distinct chromatin features called DNA loops in regulatory T cells. These loops bring genes binding to Foxp3 in close proximity to genes controlling regulatory T-cell identity, facilitating Foxp3's promotion of identity-forming gene expression.
"We wanted to see whether Foxp3 was benefiting from DNA loops that the regulatory T cell chromatin structure was already making, or if Foxp3 was in some way creating those characteristic loops," explains Zhi Liu, co-first author and former postdoctoral researcher in Zheng’s lab. "We found that Foxp3 was necessary in creating the loops, and therefore necessary in creating the chromatin architecture unique to regulatory T cells."
Implications for Immunotherapy
The study not only underscores Foxp3's role as a genetic switch but also reveals its broader influence on the genetic structure of regulatory T cells. This newfound understanding of Foxp3's role offers potential pathways for modulating immunosuppression. Dixon, the co-senior author of the study, suggests, "If we turn up Foxp3, we could see more immunosuppression, which could treat autoimmunity. If we turn down Foxp3, we could see less immunosuppression, which could be helpful in fighting cancerous tumors, since normally regulatory T cells infiltrate tumors and suppress the action of other immune cells."
A Continuation of Discovery
Further research is required to unravel how Foxp3 collaborates with other proteins to create DNA loops in regulatory T cells. As researchers delve deeper into the relationship between Foxp3 and regulatory T cells, they hope Foxp3 will emerge as a viable target for therapies aimed at regulating immunosuppression. This work opens doors to novel approaches in treating autoimmune diseases and cancer, highlighting the nuanced interplay between our genetic makeup and immune function.