Final answer:
Interferon-gamma (IFN-γ) is the cytokine that regulates cell-mediated immune responses. It enhances the activity of cytotoxic T cells and activates macrophages.
Step-by-step explanation:
The cytokine that regulates cell-mediated immune responses is Interferon-gamma (IFN-γ). Interferon-gamma is primarily produced by activated T cells and Natural Killer (NK) cells. It plays a crucial role in enhancing the activity of cytotoxic T cells and activating macrophages to eliminate infected cells.
For example, when a virus infects a cell, the infected cell releases Interferon-gamma to signal nearby cells and activate their immune response. These neighboring cells then produce compounds that interfere with viral replication, enhance phagocytosis, and recruit other immune cells to fight the infection.