Medicine & USMLE

B-Cell Activation

  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


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)