Regulatory T-cells, or Tregs, are white blood cells that modulate the body’s immune response. A growing body of evidence points to the role of immune activation in mood disorders, such as anxiety and depression. A new study in mice shows that Foxp3, a transcription factor, influences Treg expression and activity, ultimately influencing mood.

Researchers depleted the Foxp3-expressing cells in mice and assessed the animals' behavior. They found that Foxp3 depletion caused temporary anxiety and depression-like behaviors due to the activation of inflammasomes, multi-protein complexes that drive the body’s inflammatory response.

Then, the researchers restored Foxp3-expressing cells in the mice and found that the anxiety and depression-like behaviors improved. They also noted changes in the innate immune system, including increased activity of caspase-1 (a protein that initiates the immune response) and release of interleukin-1β (a pro-inflammatory cytokine) in the brain.

These findings suggest that Foxp3 plays a causal role in regulating the immune response, which, in turn, can affect the brain’s innate immune system. They also highlight potential mechanisms that may contribute to anxiety and depression. However, this research was conducted in mice, and extrapolating these findings to humans requires further investigation. Learn about some of the underlying mechanisms that drive depression in this short video.

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