CytokinesIntercellular mediators regulating host defense
National Cancer Institute, USA
Cytokines are intercellular peptide signals that can be produced by every nucleated cell type and engage in host defense against invasive organisms and repair of damaged tissues. Cytokines have pleiotropic regulatory effects on hematopoietic and other cell types and interact with host cell receptors resulting in signal transduction and consequent... read moreselective gene activation. Cytokines usually act over short distances in a paracrine manner in local tissues, but when present in the circulation can induce systemic effects such as hematopoiesis, fever and malaise. Cytokines are generally not produced constitutively, but are generated in response to “danger signals” to fend off challenges to the integrity of the host with the goal of restoring homeostasis by regulating innate and adaptive immune responses.
Many cytokines (over 300) including chemotactic cytokines (chemokines) and growth factors and their receptors have been identified as distinct gene products to date. Many of these mediators are multifunctional making it imperative to determine their roles based largely on in vivo studies including studies of inhibitors, antagonists and gene deleted (knockout) mice. The effects of cytokines regulate not only the cells of the immune system, but also tissue development such as angiogenesis, differentiation of cells involved in hematopoiesis, bone formation and resorption , antiviral defense, fibroplasias and numerous other activities. Furthermore, cytokines have therapeutic efficacy in some diseases, but inhibitors of cytokines have been even more effective in countering tissue damage due to overproduction in some autoimmune diseases and syndromes due to genetic defects.