What is "cytokine"?

Cytokine is a small protein secreted by various cells in the human body, including immune cells, and plays a crucial role in cell signaling and regulation of immune responses. They act as chemical messengers, coordinating and modulating the immune system's activities, such as inflammation, cell growth, and differentiation. Cytokines help facilitate communication between different cells and are essential for maintaining proper immune function and homeostasis in the body.