Plasma Cells Drive Secondary Antibody Surge

Steps:

• Primary exposure to antigens activates naive B cells, forming plasma cells for initial antibodies and B-memory cells for long-term immunity.
• Secondary exposure reactivates B-memory cells, which rapidly differentiate into many plasma cells.
• These new plasma cells produce antibodies at a higher rate and quantity than in the primary response.
• The direct increase in antibody output stems from this expanded plasma cell population.

Why C is correct:

• Plasma cells are effector B cells specialized to secrete large volumes of antibodies, directly causing the amplified production in secondary responses per immunological definitions of humoral immunity.

Why the others are wrong:

• A. B-memory cells: They store immune memory and trigger plasma cell formation but do not produce antibodies themselves.
• B. Macrophages: They engulf pathogens and present antigens to activate immune cells, not produce antibodies.
• D. T-memory cells: They enhance cell-mediated responses against intracellular threats, not antibody production.

Final answer: C