USMLE

T-Cell Stages

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Immunology
  1. Innate Immunity
  2. Adaptive Immunity
  3. Macrophages
  4. Neutrophils
  5. Dendritic Cells
  6. Mast Cells
  7. Eosinophils
  8. Basophils
  9. Natural Killer Cells
  10. Antigens
  11. MHC I and II
  12. Antibodies
  13. B Lymphocytes Overview
  14. B Cell Stages
  15. B-Cell Activation
  16. Plasma B-Cells
  17. Memory B-Cells
  18. T-Lymphocytes Overview
  19. T-Cell Stages
  20. Types of Activated T-Cells

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