New cytokines are being rapidly identified and new functions and activities described in known cytokines. Despite the seemingly confusing nomenclature, some common characteristics exist and permit distinction of certain groups of molecules. Interactions among cytokines and the impact of cell surface receptor ligand interaction on intracellular cytokine signaling is increasingly appreciated. Dissection of the signaling pathways is vital to understand the role of cytokines and growth factors in a variety of disease states. Hematopoietic growth factors are already in widespread clinical use.
New therapies based on understanding crucial parts of the signaling process are under investigation.
Further study of cytokines and hematopoietic growth factors and the interactions among them will provide new possibilities for more targeted treatments in the future. It is a highly pleiotropic cytokine that mediates apoptosis, cell proliferation, immunomodulation, inflammation, viral replication, allergy, arthritis, septic shock, insulin resistance, autoimmune diseases, and other pathological conditions. While TNF is an integral part of the immune system and is required for host defense, its inappropriate production can be lethal, making it a double-edged sword. The signaling mechanisms of endothelial cell proliferation, migration, and hyperpermeability and the role of the anti-apoptotic AKT pathway in endothelial survival are areas of active research. PDGF and PDGF receptor expression patterns, the use of antagonists, and genetic approaches involving targeted inactivation of PDGF and PDGF receptor genes have implicated PDGFs as critical factors in a number of developmental and disease processes.