Combine the concepts of HPA axis activation and cortisol's role to explain the suppression of lymphocyte production during stress.

• A. Cortisol has no role in lymphocyte production during stress.
• B. HPA axis activation directly increases lymphocyte production.
• C. HPA axis activation decreases cortisol, enhancing lymphocyte production.
• D. HPA axis activation leads to increased cortisol, which signals the body to suppress lymphocyte production.

Answer: (D)