USMLE

B-Cell Activation

565 views
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

B-cell activation describes the steps needed to turn on B-cells, to generate an antibody response to a threat. This process starts with resting B-cells engulfing foreign particles via endocytosis in the lymph nodes. After engulfing these particles,  B-cells process and digest them into smaller fragments called antigens inside the cell, and present these antigens on a surface complex called MHC II. Once displayed on MHC 2, helper T-cells will recognize the antigen to determine if it is a threat. If the T-cell finds a threat, it will release cytokines, which act as signals to activate the B-cell. B-cell activation involves proliferation or multiplication of B-cells, as well as differentiation of these B-cells into their active forms in order to produce antibodies against the threat.

Key Points

  • B-cell Activation
    • Upon antigen binding to B-cell receptors, the B-cell:
      • (1) endocytoses the antigen, then breaks it down into smaller fragments
      • (2) presents the antigen fragments on its surface to helper T cells.
      • (3) Helper T-cells release cytokines (signaling molecules) to activate the B-cell
      • (4) Activated B-cell then proliferates and turns into plasma or memory cells (see video)