A major action of cytokines is to function as chemical messengers that recruit immune cells.

• A. Directly destroy pathogens
• B. Act as chemical messengers to recruit immune cells
• C. Suppress immune response
• D. Build scar tissue

Answer: (B)

Cytokines function as chemical messengers that coordinate the immune response by signaling other cells. This signaling directs where immune cells should go and how they should behave, which is essential for mounting an effective defense. In this context, chemokines—a subset of cytokines—create chemical gradients that recruit neutrophils, monocytes, T cells, and other immune cells to sites of infection or injury. While cytokines can influence other processes, such as promoting inflammation or activating cells, their primary role highlighted here is guiding immune cell recruitment to orchestrate the response. Direct pathogen destruction comes from effector cells and mechanisms, not cytokines themselves, and activities like suppressing the immune response or building scar tissue are more specific effects of particular cytokines rather than the general, central action described.