Since the early nineties , research is the interactions between the nervous system and the immune system. Substances that may affect these processes include glucocorticosteroids , opioid peptides , polypeptides , hormones, pituitary and catecholamines . Catecholamines inhibits the activity of T lymphocytes and B and produce anti-tumor immune response . Proving in 1994, the presence and biosynthesis of catecholamines in cells of the immune system has become an important step in the research links between the nervous system and the immune system.