Winners of the 2018 Nobel Prizes, including Kyoto University professor Tasuku Honjo (front, C) and University of Texas professor James Allison (front, 2nd from L), who jointly received the prize in physiology or medicine, attend an award ceremony in Stockholm on Dec. 10, 2018. (Kyodo via AP Images) ==Kyodo

Winners of the 2018 Nobel Prizes, including Kyoto University professor Tasuku Honjo (front, C) and University of Texas professor James Allison (front, 2nd from L), who jointly received the prize in physiology or medicine, attend an award ceremony in Stockholm on Dec. 10, 2018. (Kyodo via AP Images) ==Kyodo

Winners of the 2018 Nobel Prizes, including Kyoto University professor Tasuku Honjo (front, 4th from L) and University of Texas professor James Allison (front, 3rd from L), who jointly received the prize in physiology or medicine, attend an award ceremony in Stockholm on Dec. 10, 2018. (Pool photo) (Kyodo via AP Images) ==Kyodo

Winners of the 2018 Nobel Prizes, including Kyoto University professor Tasuku Honjo (front, 2nd from R) and University of Texas professor James Allison (front, 3rd from R), who jointly received the prize in physiology or medicine, attend an award ceremony in Stockholm on Dec. 10, 2018. (Pool photo) (Kyodo via AP Images) ==Kyodo

Winners of the 2018 Nobel Prizes, including Kyoto University professor Tasuku Honjo (front, C) and University of Texas professor James Allison (front, 2nd from L), who jointly received the prize in physiology or medicine, attend an award ceremony in Stockholm on Dec. 10, 2018. (Pool photo)(Kyodo via AP Images) ==Kyodo