Question

Humoral immunity is produced by

• A. Cytotoxic T cells
• B. B cells
• C. Memory T cells
• D. Helper T cells

Hint:

Remember: "Humoral" refers to bodily fluids (humors). Because antibodies circulate dissolved in these fluids to fight extracellular pathogens, antibody-producing B cells are the mediators of humoral immunity.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The adaptive immune system is divided into two main branches: humoral immunity and cell-mediated immunity.
Humoral immunity protects against extracellular pathogens and toxins using macromolecules (such as antibodies) dissolved in bodily fluids.

Step 2: Detailed Explanation:
Let us analyze the roles of the listed lymphoid cells:
B Cells (B Lymphocytes): These cells are the mediators of humoral immunity.
When a naive B cell encounters its specific antigen, it internalizes it, presents it to helper T cells, and undergoes activation and clonal expansion.
These activated B cells differentiate into antibody-secreting plasma cells and long-lived memory B cells.
The secreted antibodies (immunoglobulins) circulate in the blood and lymph, binding specifically to foreign antigens to neutralize them, promote phagocytosis (opsonization), or activate the complement system.
T Cells (T Lymphocytes): These cells mediate cell-mediated immunity:
- Cytotoxic T Cells (CD8+): Destroy virus-infected or cancerous host cells directly.
- Helper T Cells (CD4+): Secrete cytokines that coordinate the activities of other immune cells, including B cells and macrophages.
Therefore, humoral immunity is produced by B cells.

Step 3: Final Answer:
Humoral immunity is produced by B cells.