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Baruj Benacerraf specialized in immunology. He was a Venezuelan-American immunologist and a Nobel laureate. He shared the 1980 Nobel Prize in Physiology or Medicine with Jean Dausset and George D. Snell for their discoveries of the major histocompatibility complex. Benacerraf showed that the immune system could distinguish between self and non-self cells. This discovery helped to explain the rejection of transplanted organs.