the origins of immunology -- 10/25/23
Today's selection -- from An Elegant Defense by Matt Richtel. Immunology and phagocytosis:
“A case can be made that the field of immunology originated with a chicken.
“The setting was the University of Padova in northern Italy, at the end of the sixteenth century. There was at that time a young researcher named Fabricius ab Aquapendente who liked to cut things up. He dissected eyes, ears, animal fetuses, and occasionally humans. But history remembers him for a chicken.
“Dissecting a fowl one day, Fabricius noticed an odd region beneath the chicken's tail. He found a saclike organ, which he called the bursa, a word that shares its derivation with the modern word purse. Henceforth, the bursa of Fabricius.
“This thing appeared to have no purpose. What the heck was it? Why would God (this was the sixteenth century) leave on a bird a saclike purse that didn't seem to do anything?
“Would Fabricius have believed it held the key to understanding our survival? Could he have known this simple observation would someday save the lives of millions of people, including Jason's?
“So too it would be for a handful of other seemingly unconnected discoveries that would build the foundation of our understanding of our immune system.
“On July 23, 1622, an Italian scientist named Gaspare Aselli dissected a ‘living well-fed dog,’ recounts one history of this seminal surgery. In its stomach, he observed ‘milky veins.’ This observation wasn't consistent with an understanding of a circulatory system carrying red blood. Instead, these milky veins looked like they contained white blood. Aselli's dissection set off a period of exploration that the history calls lymphomania, a fascination with a little understood bodily fluid called lymph, along with the dissection and vivisection of hundreds of animals.
“The role of the milky veins wasn't clear for many years. As Nature magazine put it centuries later, Aselli's observation ‘languished in relative obscurity for decades.’
“What was this alternate circulatory system?
“In northeast Sicily in the summer of 1882, Elie Metchnikoff peered through a microscope. Metchnikoff was a zoologist from Odessa who had gone to Italy to visit with his sister and her family during a period when trouble was brewing in Russia. Jewish farmers faced intensifying persecution from the government and peasants. At one point, the peasants murdered a farmer. Metchnikoff took his microscope to Sicily, where lightning struck: ‘The great event of my scientific life took place.’
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| Ilya Ilyich Mechnikov in his laboratory |
“The name Fabricius will be forever linked to the chicken bursa. For Metchnikoff, the association is with a starfish larva. This was the medium of his great observation.
“One day while his family was at the circus--’to see some extraordinary performing apes’--Metchnikoff turned his microscope on embryonic starfish, which are transparent. He noticed cells moving throughout the tiny organisms. He described them as "wandering cells," and he was struck by an instant of revelation.
“‘A new thought suddenly flashed across my brain. It struck me that similar cells might serve in the defence of the organism against an intruder,’ he wrote.
“He had an idea how to figure it out. What if, he wondered, he put a splinter into a starfish? Would cells like these somehow swarm, as if coming to the rescue?
“'There was a small garden to our dwelling, in which we had a few days previously organised a "Christmas tree" for the children on a little tangerine tree; I fetched from it a few rose thorns and introduced them at once under the skin of some beautiful star-fish larvae as transparent as water. I was too excited to sleep that night in the expectation of the result of my experiment, and very early the next morning I ascertained that it had fully succeeded.'
“Indeed, a bunch of these wandering cells swarmed around the splinter. They appeared to eat away at the offending or troubled tissue.
“That experiment formed the basis of the phagocyte theory, to the development of which I devoted the next twenty-five years of my life.
“The word phagocyte is taken from the Greek and can be roughly translated as ‘devourer of cells.’
“Phagocytosis is the process by which the devouring happens."
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