Dr. Honjo is well known for his discovery of AID that is essential for class switch recombination and somatic hypermutation. He has established the basic conceptual framework of class switch recombination. In addition, he discovered PD-1, a negative coreceptor at the effector phase of immune response and showed that PD-1 modulation contributes to treatments of tumor, viral infection and autoimmunity. For these contributions, Dr. Honjo has received many awards, including the Nobel Prize in Physiology or Medicine, Imperial Prize, Japan Academy Prize, Robert Koch Prize, Order of Culture, the Tang Prize, the Kyoto Prize. Elected as a foreign associate of National Academy of Sciences, USA, as a member of the German Academy of Natural Scientists, and also as a member of Japan Academy.