B Cell Stages

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