Baruj Benacerraf (/bɪˈnæsərəf/; October 29, 1920 – August 2, 2011) was a Venezuelan-American immunologist, who shared the 1980 Nobel Prize in Physiology or Medicine for the "discovery of the major histocompatibility complex genes which encode cell surface protein molecules important for the immune system's distinction between self and non-self.

That same year, Benacerraf attended Lycée Français de New York, where he earned a Baccalauréat (an academic qualification French students achieve after high school and a diploma necessary to begin university studies).

In spite of an excellent academic record at Columbia, I was refused admission by the numerous medical schools I applied to and would have found it impossible to study medicine except for the kindness and support of George W. Bakeman, father of a close friend, who was then Assistant to the President of the Medical College of Virginia in Richmond.

"[9] After his medical internship, US Army service (1945–48), and working at the military hospital of Nancy, France, he became a researcher at Columbia University College of Physicians and Surgeons (1948–50).

He began studying allergies in 1948, and discovered the Ir (immune response) genes that govern transplant rejection in the 1960s.

[11] He then moved to Paris because of family issues and accepted a position in Bernard Halpern's laboratory at the Hôpital Broussais.

While there they discovered techniques to study the clearance of particulate matter from the blood by the RES (reticuloendothelial system), and devised equations that govern this process in mammals.

After working in his New York lab, Baruj turned his attention towards the training of new scientists, and made the decision to devote himself to his laboratory practices, instead of the family business.

He noticed that if antigens (something that causes a reaction with the immune system) were injected into animals with a similar heredity, two groups emerged: responders and non-responders.