Cytokines are low molecular weight soluble proteins produced by cells stimulated by immunogens, mitogens or other factors, including interleukins, interferons (IFN), lymphokines, colony-stimulating factors (CSF), chemokines, monoclonal factors and other factors. They are involved in regulating intrinsic and adaptive immune response, promoting haematopoiesis, repairing damaged tissues and stimulating cell activation.