Mitochondria Lysosomes T Cell Activation
- Memphis, TN - Scientists at St.Jude Children's Research Hospital have made a meaningful breakthrough in understanding how regulatory T cells (tregs) - crucial immune cells that prevent the...
- What: Researchers identified four distinct metabolic states of regulatory T cells and the role of mitochondria and lysosomes in their activation and deactivation.
- Regulatory T cells are vital for maintaining immune homeostasis.
St. Jude Research Reveals How Immune ‘Controller’ Cells Activate & Deactivate, Offering New Therapeutic Pathways
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Memphis, TN – Scientists at St.Jude Children’s Research Hospital have made a meaningful breakthrough in understanding how regulatory T cells (tregs) – crucial immune cells that prevent the immune system from attacking the body’s own tissues – are activated and deactivated. The research,published today in Science Immunology,details the interplay between cellular metabolism,mitochondria,and lysosomes in controlling Treg function,with potential implications for treating autoimmune diseases,inflammatory disorders,and improving cancer immunotherapy.
Regulatory T cells are vital for maintaining immune homeostasis. When the immune system responds to a threat, inflammation occurs. Tregs step in to control this inflammation and restore tissues to normal. Dysfunctional Tregs can lead to uncontrolled inflammation, tissue damage, and autoimmune disorders. The importance of Tregs was recognized with the 2025 Nobel Prize in Physiology or Medicine awarded for their discovery. However, the precise molecular mechanisms governing their activation have remained elusive – until now.
“We discovered how regulatory T cells are activated and become more immunosuppressive during inflammation,” explained Dr. Hongbo Chi, chair of the Department of Immunology and co-director of the center of Excellence for Pediatric Immuno-Oncology at St. Jude. ”By defining how cellular metabolism rewires regulatory T cells through different states of activation, including their return to a resting state, we have provided a roadmap to explore future therapeutic interventions or ways to improve existing immune-related treatments.”
Metabolic States of Regulatory T Cells
The research team utilized single-cell RNA sequencing in a mouse model of inflammation to analyze gene expression related to energy production and cellular metabolism within Tregs. This revealed four distinct states:
- Quiescent: Relatively inactive metabolic state.
- Intermediately Activated: Transitioning towards higher metabolic activity.
- Highly Metabolically Activated: Peak metabolic activity and immunosuppressive function.
- Metabolic Quiescence: A newly identified state where Tregs return to a resting state, effectively “turning off” their suppressive activity.
“That final subset, which re-enters metabolic quiescence, has never been described for regulatory T cells, but may explain how these immune suppressors are ‘turned off’ when their task is done,” said Dr. Jordy Saravia, first author of the study.
The Role of Mitochondria and Lysosomes
Further examination using electron microscopy revealed a strong correlation between Treg activation state and organelle structure. More activated Tregs contained a higher number of mitochondria – the cell’s “powerhouses” - and these mitochondria exhibited increased density of cristae (folds within the mitochondria), indicating enhanced energy production.
The study also highlighted the role of lysosomes, the cell’s recycling centers, in regulating Treg function. While the precise mechanism is still under investigation, the researchers believe lysosomes are crucial for clearing metabolic byproducts and facilitating the transition between activation states.
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This research is a significant step forward in our understanding of immune regulation. For years, the field has known that Tregs are crucial, but the how of their activation and deactivation has been a major puzzle.The identification of these distinct metabolic states, and the clear link to mitochondrial and lysosomal function, provides a concrete framework for developing targeted therapies. The discovery of the ‘metabolic quiescence’ state is particularly exciting, as it suggests a mechanism for actively shutting down Treg activity, which could be crucial in situations where immune suppression is detrimental, such as in cancer. The use of single-cell RNA sequencing and electron microscopy provides a robust and multi-faceted approach to this complex biological question.
Data Summary: Mitochondrial Density & Activation State
The following table summarizes the observed correlation between mitochondrial density and Treg activation state:
| Treg Activation State | Relative Mitochondrial Density | Cristae Density |
|---|---|---|
| Quiescent | Low | Low |
| Intermediately Activated | Moderate | Moderate |