[Cytokines in bone diseases. What is cytokine?]

Cytokines have an essential role for cell-cell communication. They can regulate cell proliferation, differentiation, survival, and function. Interaction of cell surface receptor with cytokines is necessary for control of physiological responses. Activation of cytokine receptors transduces specific signal in the receptor-expressing cells, resulting that cytokines can regulate specific cell population. Thus, cytokines contribute directly or indirectly to morphogenesis, host defense and immune response, play critical roles for homeostasis and development.