1. Introduction
B cells and T cells are lymphocytes (types of white blood cells). Together, they form the adaptive immune system, which “learns” and remembers invaders like bacteria and viruses.
2. B Cells (Bone marrow–derived)
B Cells → Humoral immunity
- Develop in bone marrow.
- Turn into plasma cells that make antibodies (proteins that tag invaders).
- Create memory B cells for long-term defense after infection or vaccination.
- Also present antigens to T cells to boost immune activation.
3. T Cells (Thymus–derived)
T Cells → Cell-mediated immunity
- Develop in thymus (after being formed in bone marrow).
- Helper T cells (CD4⁺): coordinate the immune response by releasing cytokines.
- Cytotoxic T cells (CD8⁺): directly kill virus-infected or cancer cells.
- Regulatory T cells: prevent the immune system from overreacting (autoimmunity).
- Memory T cells: provide rapid future protection.
4. B Cells vs T Cells — Side by Side
| Feature | B Cells | T Cells |
|---|---|---|
| Where they mature | Bone marrow | Thymus |
| Type of immunity | Humoral (antibody-based) | Cell-mediated |
| Main weapons | Antibodies | Cytokines, direct killing |
| Best against | Bacteria, toxins, viruses outside cells | Viruses inside cells, cancer |
| Memory | Memory B cells | Memory T cells |
5. How They Work Together
- A pathogen enters the body.
- Helper T cells are activated by antigen-presenting cells.
- Helper T cells activate B cells → plasma cells make antibodies.
- Antibodies tag invaders; cytotoxic T cells kill infected cells.
- Memory B & T cells remain for future defense.
6. Clinical Relevance
- Vaccines train B & T cells to “remember” pathogens.
- Autoimmunity: T cells sometimes attack the body (e.g., Type 1 diabetes).
- HIV infection: destroys helper T cells, weakening immunity.
- Cancer therapy: CAR-T cells are engineered T cells that target tumors.