The main purpose of the present invention is to provide a novel therapeutic agent or a prophylactic agent for at least one disease or symptom selected from a group comprising the symptoms that accompany autoimmune diseases, inflammatory diseases, allergic diseases and organ transplants, said therapeutic agent or prophylactic agent being capable of artificially controlling the activity of IL-6 amplifiers and controlling the bodys immune response. The purpose of the present invention is also to provide an immunosuppressant, an inhibitor for inflammatory cytokine production and an inhibitor for IL-6 amplifiers. A compound capable of inhibiting the expression of the functions of proteins belonging to the ErbB1 pathway, which is provided as a means of resolving such problems, is able to inhibit the activity of IL-6 amplifiers, and is able to reduce the production of inflammatory cytokines such as IL-6. Consequently, a compound capable of inhibiting the functions of proteins belonging to the ErbB1 pathway can be used as the active ingredient of a therapeutic agent or a prophylactic agent for at least one disease or symptom selected from a group comprising the symptoms that accompany autoimmune diseases, inflammatory diseases, allergic diseases and organ transplants.La présente invention concerne un nouvel agent thérapeutique ou un agent prophylactique destiné au moins à une maladie ou un symptôme choisi dans un groupe comprenant les symptômes qui accompagnent les maladies auto-immunes, les maladies inflammatoires, les maladies allergiques et les greffes dorganes, ledit agent thérapeutique ou agent prophylactique étant capable de contrôler artificiellement lactivité des amplificateurs de lIL-6 et de contrôler la réponse immunitaire du corps. La présente invention concerne également un immunosuppresseur, un inhibiteur de la production des cytokines inflammatoires et un inhibiteur des amplificateurs de lIL-6. Un composé capable dinhiber lexpression des fonctions des protéine
