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What are the differences between positive and negative selection of T cells?
Posted August 18, 2023

Answer

Positive Selection of T-cells: 

  • Refers to the T cell development process in the thymus by the binding of T-cell receptors (TCRs) of mature T-cells to the self-antigens presented by Major Histocompatibility Complex (MHC) of thymocytes
  • Is responsible for the maturation of thymocytes
  • Results in the maturation of thymocytes into either CD8+ (cytotoxic) T-cells or CD4+ (helper) T-cells 
  • Antigen presentation is minimal
  • Occurs in the cortex of the thymus
  • Does not have the ability to activate apoptosis
  • Does not suppress autoimmune reactions
  • Occurs before negative selection 

Negative Selection of T-cells: 

  • Refers to the process of T cell development in thymus due to the incapability of TCRs to bind the MCH complexes of thymocytes
  • Prevents the formation of self-reactive T-cells
  • Results in the cell death of thymocytes 
  • Occurs in the medulla of the thymus
  • Has the ability to activate apoptosis following strong interactions between T-cell and self antigen
  • Suppresses autoimmune reaction as it does not produce self-reacting cells
  • Takes place after positive selection