USMLE

B 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

The maturation of B-cells involves several steps that occur in different locations through the body. Like all blood cells, B-cells are initially created in the bone marrow. However, after creation, B-cells are notable for remaining inside the bone marrow to mature. During maturation, B-cells undergo a 2-step process of clonal selection. The first step is positive selection, which only allows B-cells that can recognize MHC molecules to survive. Positive selection ensures that B-cells can actually do their job and recognize antigen on MHC. After positive selection comes negative selection, in which B-cells that bind MHCs carrying self-antigens too tightly get eliminated. This ensures that self-reactive B-cells that could cause autoimmunity get destroyed. The remaining B-cells that pass both steps are now known as mature but naive B-cells, and these completed mature cells migrate to lymph tissues where they lie in wait for a specific antigen to activate them.

Key Points

  • B Cell Stages
    • Development occurs in stages
      • Produced in bone marrow
      • Matures in bone marrow
        • Undergo a 2-step process of clonal selection
          • Positive selection tests whether B cells can successfully recognize MHC molecules
            • Failure in positive selection makes antibodies unable to bind antigen or launch adaptive immune response against foreign invaders
          • Negative selection tests whether B cells can avoid association with self-antigens 
            • Failure in negative selection results in self-reactive or autoimmune diseases.
      • Surviving naive B-cells (unactivated) reside in lymph tissues (lymph nodes, spleen, tonsils)
      • Activated B-cells proliferate and differentiate into plasma or memory B-cells