Cell signalling proteins
Cytokines are small proteins secreted by cells that aid cell to cell signalling, including communication in immune responses and stimulating the movement of cells towards sites of inflammation, infection and trauma. Among the many functions of cytokines are the control of cell proliferation and differentiation, and the regulation of angiogenesis and immune and inflammatory responses. The term "cytokine storm" has appeared in medical research since at least 1993, and became popularised in the context of human to human avian H5N1 influenza virus, and later in the COVID-19 pandemic of 2019 and onward.
