Medicine & USMLE

B Cells - Overview

B Cells and T Cells
  1. MHC I
  2. MHC II
  3. B Cells - Overview
  4. B Cells - Activation
  5. Plasma B Cells
  6. Memory B Cells
  7. T Cells - Overview
  8. T Cells - Activation
  9. T Cells - Differentation
  10. Cytotoxic (Killer) T Cells
  11. Helper T Cells - Overview
  12. Th1 Cells
  13. Th2 Cells
  14. Th17 Cells
  15. Regulatory T Cells (Tregs)


B-cells are lymphocytes which produce antibodies, mediating humoral immunity. B-cells can be identified by their expression of CD19 and CD20, surface markers that also serve as drug targets in B-cell mediated diseases. B-cells originate and mature in the bone marrow and later migrate to lymphoid tissues, where they reside to wait for antigens. Once activated against an antigen, B-cells mediate the humoral immune response by producing antibodies.

Key Points

  • B Cells
    • Lymphocytes of the adaptive immune system
      • Must be activated against a specific antigen
    • Mediate humoral immunity (make antibodies)
    • Express CD19 and CD20
      • CD20 is important as drug target of Rituximab
    • Originate from and mature in the bone marrow
    • Migrate to and reside in lymphoid tissue
      • e.g. follicles of lymph nodes, white pulp of spleen, unencapsulated lymphoid tissue
    • After B-Cell Activation by an antigen, they differentiate into: