T Cells and Regulatory T Cells

T Cells and Regulatory T Cells

  • Context: 

  • The 2025 Nobel Prize in Physiology or Medicine was awarded to the U.S based researchers Mary E. Brunkow and Fred Ramsdell, along with Japan's Shimon Sakaguchi, for their discoveries concerning "peripheral immune tolerance".  

  • Their work identified Regulatory T cells which provide a fundamental understanding of how the immune system is regulated and kept in check to prevent it from attacking the body's own tissues.  

  • What are T Cells? 

  • T cells (Thymus-derived lymphocytes) are a type of white blood cell that plays a central role in the adaptive immune system.  

  • They originate from stem cells in the bone marrow and mature in the thymus gland (which is how they get their name) 

  • T cells are responsible for immune-mediated cell death.  

  • They attack invading pathogens and infected host cells.  

  • Unlike other lymphocytes, they possess a unique T-cell receptor (TCR) on their surface that scans other cells to detect invaders.  

  • They require antigens to be presented to them by Major Histocompatibility Complex (MHC) molecules on other cells to get activated.  

  • What are Regulatory T Cells (Tregs)? 

  • Regulatory T cells are a specialized subpopulation of T cells that act to suppress the immune response, thereby maintaining immunological tolerance and preventing autoimmune diseases.  

  • They are the immune system's "security guards," preventing other immune cells from mistakenly attacking the body's own tissues. 

  • Formation:  

  • Regulatory T cells can be formed either during T cell development in the thymus (called thymic Treg cells) or can be induced in peripheral tissues (called peripherally derived Treg cells) 

  • Discovery: 

  • Shimon Sakaguchi first identified a new class of T cells that carried an extra protein called CD25 on their surface, which he named regulatory T cells. 

  • Brunkow and Ramsdell later identified the crucial gene, Foxp3, which controls the development and function of these regulatory T cells.  

  • Mutations in the human equivalent of this gene cause a serious autoimmune disease called IPEX. 

  • Function: 

  • They shut down T-cell mediated immunity at the end of an immune response. 

  • They suppress "autoreactive" T cells that could potentially attack the body's own cells.  

  • They ensure the immune system calms down after it has successfully fought off invaders.