T-Cell Stages

Summary

T-cells mature in several stages, which take place in different parts of the body. Like all blood cell types, T-cells are originally produced in the bone marrow. After their creation, immature T-cells then migrate to the thymus, where they undergo positive and negative selection. These selection processes ensure that T-cells can recognize antigens, and that self-reactive T-cells which might cause autoimmunity are eliminated. The T-cells that successfully pass this maturation process are finally mature, and these mature T-cells migrate to the lymph tissues, where they encounter antigens and become activated.

Key Points

• T Cell Stages
  • Development in stages
    • Immature T-cells produced in bone marrow
    • Matures in thymus
      • Undergo a 2-step process of clonal selection
        • Positive selection tests whether T cells can successfully recognize MHC molecules. 
          • Failure in positive selection makes T cells unable to bind antigen or launch adaptive immune response against foreign invaders
        • Negative selection tests whether T cells can avoid association with self-antigens 
          • Failure in negative selection results in self-reactive or autoimmune diseases.
    • Naive T-cells (unactivated) reside in lymph tissues (lymph nodes, spleen, tonsils)
    • Activation causes proliferation and differentiation into cytotoxic, helper, or memory T-cells