[6] He was interested in becoming a physician at a young age, and his father, who wanted to study medicine but could not due to financial reasons, encouraged him to do so.

[6] In 1960, Cooper went to Hospital for Sick Children, London as pre-registration house officer and then research assistant until 1961.

[9] He is also a professor at the Winship Cancer Institute[13] and the Emory Vaccine Center,[14] and an Eminent Scholar at the Georgia Research Alliance.

[21] The experiments showed irradiated chicks with the bursa removed did not have plasma cells, antibodies, and germinal centers, despite their intact thymus.

Conversely, irradiated chickens with the thymus removed had low lymphocyte levels, but had normal antibodies, plasma cells, and germinal centers.

[24] Again working on chickens, Cooper also made a contribution to deducing how B cells produce different types of antibodies at different stages of embryonic development, in the sequence of IgM, IgG, and IgA.

Collaborating with John Owen from the UK, Cooper used a series of experiments to determine the mammalian organ equivalent to the bursa and found that B cells are produced in the liver of fetal mice.

[30] More recently, Cooper studied the adaptive immune system in jawless vertebrates, including lampreys and hagfish.