Peyton Rous was a young pathologist at the Rockefeller Institute in New York in 1910 when a local chicken farmer came in carrying a Plymouth Rock hen with a mysterious lump on its breast. Rous diagnosed the condition as a sarcoma, or tumour of the connective tissues. He found that the tumour could be transmitted to healthy chickens of the same breed via the injection of cancerous tissue, and discovered that the cancer became more aggressive on each transmission.
He decided to go a step further. He minced the tissue in saline solution, filtered it so that it did not contain any whole cancer cells or bacteria and injected the filtered extract into healthy hens. Again, tumours appeared in the healthy chickens and Rous suggested in a seminal paper published in 1911 that the tumour-inducing agent was a “minute parasitic organism” – in other words a virus. Little was known about viruses at the time and the idea that they could cause cancer was controversial to say the least.
However, Rous abandoned cancer research until the 1930s when colleagues at the Rockefeller discovered another tumour caused by a virus – this time isolated from a papilloma, or wart, found in rabbits. His earlier work was vindicated when, in the 1950s, the Rous sarcoma virus (RSV) became a widely accepted tool in immunology for inducing cancers in experimental animals, more reliably so than radiation or carcinogenic chemicals. A decade later, scientists found the key gene of the retrovirus that leads to the formation of a tumour, and at the same time Rous himself won a half share of a Nobel Prize for his role in the discovery of a viral cause of cancer.
But the role of chickens in immunology didn’t end there. Bruce Glick was a graduate student at the University of Ohio in the mid-1950s and was trying to discover the role of the “bursa of Fabricius”, a small appendix-like organ in the tail end of a hen’s digestive tract. When Glick removed the bursa of newly-hatched, white leghorn chicks, the adult hens didn’t seem to be affected in any way. Puzzled, he finally gave up and returned the bursa-less chickens to the university’s general stock of hens.
Then another graduate student, teaching assistant Tony Chang, needed a few chickens to demonstrate the production of antibodies. He failed to get the bursa-less hens to produce antibodies – to his immense surprise and annoyance. The two students quickly realised this mysterious organ was crucial for antibody production and submitted a paper to the journal Science, which unfortunately rejected it as “uninteresting”. It was finally published in Poultry Science in 1955 where it languished for many years before becoming one of the most cited papers in immunology.
Thanks to Glick, Chang and the chicken we now know that a bird’s bursa plays a key role in producing the antibody-secreting B cells of the immune system. The equivalent organ in humans where B cells are produced is the bone marrow. But the “B” in B cells actually derives from “bursa” rather than “bone” – an etymological tribute to our feathered friend.