Cytokines are low molecular weight soluble proteins induced by immune antigens, mitogens, or other stimuli that regulate innate and adaptive immunity, hematopoiesis, cell growth, pluripotent stem cells, tissue repair, and other functions. Cytokines can be classified as interleukins, interferons, tumor necrosis factor superfamily, colony-stimulating factors, chemokines, growth factors, etc. They exert their effects in the body through paracrine, autocrine, or endocrine mechanisms, exhibiting pleiotropy, redundancy, antagonism, synergism, forming a complex cytokine regulatory network involved in various essential physiological functions.
Cytokines play a crucial role in the development, differentiation, immune response, and immune regulation of immune cells. However, they can also act as a "double-edged sword," participating in the onset of various diseases under certain conditions. For instance, during immune responses, immune cells secrete large amounts of cytokines, which in turn stimulate immune cells. If this positive feedback regulation fails, it can lead to a "cytokine storm," occurring in diseases such as acute respiratory distress syndrome, SARS (severe acute respiratory syndrome), and influenza.
