How is the immune system kept in check?, Pg11.

Key Highlights:

• The Nobel trio discovered Regulatory T cells (Tregs) that prevent the immune system from attacking the body’s own tissues.
• Their findings explained why the immune system does not overreact, offering insights into autoimmune diseases such as Type-1 diabetes, rheumatoid arthritis, and multiple sclerosis.
• The research also enabled development of targeted cancer immunotherapies that modulate immune response.
• Tregs were found to carry a unique protein called CD25, later linked to the gene Foxp3, which controls their function.
• The concept of “peripheral immune tolerance” describes how T cells are regulated even outside the thymus to avoid autoimmunity.

Detailed Insights:

• Discovery Context:
  • The immune system must balance defense against pathogens and tolerance towards self.
  • Bluestone and Ramsdell’s experiments identified the genetic control of regulatory mechanisms preventing self-attack.
  • Sakaguchi’s early 1980s research in Japan revealed that removing certain T cells led to autoimmunity, proving their protective role.
• Mechanism:
  • Regulatory T cells (Tregs) form a small subset of immune T cells that express Foxp3 gene and CD25 protein.
  • They suppress overactive immune responses and signal other immune cells to stop attacking.
  • In cancer, these cells can be inhibited to allow the immune system to attack tumor cells; in autoimmune diseases, they can be enhanced to calm inflammation.
• Clinical Applications:
  • Over 200 clinical studies are ongoing using Treg-based therapy for diseases like Type-1 diabetes, Crohn’s disease, and graft rejection.
  • Checkpoint inhibitors and CAR-T therapy also build on these principles, modulating immune activation.

Scientific/Technical Concepts Involved:

• T Cells: White blood cells central to immune defense; some attack pathogens, others (Tregs) prevent autoimmunity.
• Foxp3 Gene: Master regulator for Treg cell development and function.
• Peripheral Immune Tolerance: The ability of the immune system to avoid reacting destructively to self-antigens outside primary lymphoid organs.