Secondary immune responses upon a second exposure to a pathogen are due to the activation of which type of cells?

• A. Dendritic cells
• B. Erythrocytes
• C. Memory lymphocytes
• D. Naive B cells

Answer: (C)

Verified step by step guidance

1. Understand that the immune system has two main types of responses: primary and secondary. The primary response occurs when the body encounters a pathogen for the first time, while the secondary response happens upon subsequent exposures.
2. Recall that during the primary immune response, naive B cells and T cells are activated to fight the pathogen and some of these cells differentiate into memory cells.
3. Recognize that memory lymphocytes (both memory B cells and memory T cells) are long-lived cells that 'remember' the specific pathogen encountered during the primary response.
4. Know that upon a second exposure to the same pathogen, these memory lymphocytes are quickly reactivated, leading to a faster and stronger immune response compared to the primary response.
5. Conclude that the secondary immune response is primarily due to the activation of memory lymphocytes, not dendritic cells, erythrocytes, or naive B cells.