The human immune system is one of the most fascinating components of the human body. As an example, once a person has contracted measles, such an individual may never develop symptoms of measles again. Despite striking advances in modern medicine in recent years together with rapid changes in the standard of living and quality of life, we are still being challenged by refractory autoimmune diseases, viral infections and cancers. Fascinated by the human immune system, we became engaged in research since the foundation of Japan Immunoresearch Laboratories Company Limited (JIMRO) in the hope of obtaining further insights into immune disorders and use such knowledge to the challenged disorders. As part of our response to the existing challenges, we have devoted major emphasis on lymphocytes, monocytes and granulocytes which are major players in immune functions. As a fruit of our endeavours, we developed a therapeutic device, the only one in the world, which selectively adsorbs granulocytes and monocytes / macrophages from the blood. In October 1999, our medical device developed and named Adacolumn received an approval from the Japan Ministry of Health, Labour and Welfare for manufacturing and marketing. At present, Adacolumn is reimbursed for the treatment of ulcerative colitis and Crohn’s disease in Japan. Currently, additional R&D projects in other autoimmune diseases are in progress in Japan, the EU and the USA for expanding both indications and market size of the Adacolumn. We will continue our efforts to develop innovative products including a novel BMT (bone marrow transplant) strategy. Our ultimate goal is to provide effective challenges to refractory diseases.